Evolutionary algorithm
You are encouraged to solve this task according to the task description, using any language you may know.
Starting with:
- The
targetstring:"METHINKS IT IS LIKE A WEASEL". - An array of random characters chosen from the set of upper-case letters together with the space, and of the same length as the target string. (Call it the
parent). - A
fitnessfunction that computes the ‘closeness’ of its argument to the target string. - A
mutatefunction that given a string and a mutation rate returns a copy of the string, with some characters probably mutated. - While the
parentis not yet thetarget:
- copy the
parentC times, each time allowing some random probability that another character might be substituted usingmutate. - Assess the
fitnessof the parent and all the copies to thetargetand make the most fit string the newparent, discarding the others. - repeat until the parent converges, (hopefully), to the target.
- copy the
- See also
- Wikipedia entry: Weasel algorithm.
- Wikipedia entry: Evolutionary algorithm.
Note: to aid comparison, try and ensure the variables and functions mentioned in the task description appear in solutions
A cursory examination of a few of the solutions reveals that the instructions have not been followed rigorously in some solutions. Specifically,
- While the
parentis not yet thetarget:
- copy the
parentC times, each time allowing some random probability that another character might be substituted usingmutate.
- copy the
Note that some of the the solutions given retain characters in the mutated string that are correct in the target string. However, the instruction above does not state to retain any of the characters while performing the mutation. Although some may believe to do so is implied from the use of "converges"
(:* repeat until the parent converges, (hopefully), to the target.
Strictly speaking, the new parent should be selected from the new pool of mutations, and then the new parent used to generate the next set of mutations with parent characters getting retained only by not being mutated. It then becomes possible that the new set of mutations has no member that is fitter than the parent!
As illustration of this error, the code for 8th has the following remark.
Create a new string based on the TOS, changing randomly any characters which don't already match the target:
NOTE: this has been changed, the 8th version is completely random now
Clearly, this algo will be applying the mutation function only to the parent characters that don't match to the target characters!
To ensure that the new parent is never less fit than the prior parent, both the parent and all of the latest mutations are subjected to the fitness test to select the next parent.
11l
<lang 11l>V target = Array(‘METHINKS IT IS LIKE A WEASEL’) V alphabet = ‘ ABCDEFGHIJLKLMNOPQRSTUVWXYZ’ V p = 0.05 V c = 100
F neg_fitness(trial)
R sum(zip(trial, :target).map((t, h) -> Int(t != h)))
F mutate(parent)
R parent.map(ch -> (I random:() < :p {random:choice(:alphabet)} E ch))
V parent = (0 .< target.len).map(_ -> random:choice(:alphabet)) V i = 0 print((‘#3’.format(i))‘ ’parent.join(‘’)) L parent != target
V copies = ((0 .< c).map(_ -> mutate(:parent))) parent = min(copies, key' x -> neg_fitness(x)) print((‘#3’.format(i))‘ ’parent.join(‘’)) i++</lang>
- Output:
0 FGUQJPIPMOUSPW MRHJQMNLF GZP 0 FGURJPIPMOUSPW LRHJQMSLF GZP 1 FGURJPIPMOUSPW LRHJQASLF GLP 2 FGURJPIPMOUSPW LRHJQASWFYGLP 3 FGURZPKZMOUSPW LRHJQASWFYGLP 4 FJUHZPKZMOUSPW LRHJQASWFYGLP 5 FJUHZNKZMOUSPW LRHJQASWFYGLP 6 FJUHZNKZMOUSPW LRHJBASWFYGLP 7 FJUHZNKSMOUSPW LRHJBASWFYGLP 8 FJUHKNKSMOU PW LRHJBABWFYGLP 9 FJUHKNKSMOU PW LRHJBABWFYGLL 10 FJUHKNKSMOU PW LRKJBABWFYGLL ... 76 METHINKS IT IS LIKE A WEASEL
8080 Assembly
<lang 8080asm>MRATE: equ 26 ; Chance of mutation (MRATE/256) COPIES: equ 100 ; Amount of copies to make fname1: equ 5Dh ; First filename on command line (used for RNG seed) fname2: equ 6Dh ; Second filename (also used for RNG seed) org 100h ;;; Make random seed from the two CP/M 'filenames' lxi b,rnddat lxi h,fname1 xra a call seed ; First four bytes from fn1 make X call seed ; Second four bytes from fn1 make A mvi l,fname2 call seed ; First four bytes from fn2 make B call seed ; Second four bytes from fn2 make C ;;; Create the first parent (random string) lxi h,parent mvi e,tgtsz-1 genchr: call rndchr ; Get random character mov m,a ; Store it inx h dcr e jnz genchr mvi m,'$' ; CP/M string terminator ;;; Main loop loop: lxi d,parent push d call puts ; Print current parent pop h ; Calculate fitness call fitnes xra a ; If it is 0, all characters match, ora d rz ; So we stop. lxi h,kids ; Otherwise, set HL to start of children, mvi a,0FFh ; Initialize maximum fitness value sta maxfit mvi a,COPIES ; Initialize copy counter sta copies ;;; Make copies copy: push h ; Store the place where the copy will go call mutcpy ; Make a mutated copy of the parent pop h ; Get the place where the copy went push h ; But keep it on the stack call fitnes ; Calculate the fitness of that copy pop h ; Get place where copy went lda maxfit ; Get current best fitness cmp d ; Compare to fitness of current copy jc next ; If it wasn't better, next copy shld maxptr ; If it was better, store pointer mov a,d sta maxfit ; And new max fitness next: lxi b,tgtsz ; Get place for next copy dad b xchg ; Keep in DE lxi h,copies dcr m ; Any copies left to make? xchg jnz copy ; Then make another copy lhld maxptr ; Otherwise, get location of copy with best fitness lxi b,parent ; Make that the new parent pcopy: mov a,m ; Get character from copy inx h stax b ; Store into location of parent inx b cpi '$' ; Check for string terminator jnz pcopy ; If it isn't, copy next character jmp loop ; Otherwise, mutate new parent ;;; Make a copy of the parent, mutate it, and store it at [HL]. mutcpy: lxi b,parent mcloop: ldax b ; Get current character inx b mov m,a ; Write it to new location inx h cpi '$' ; Was it the string terminator? rz ; Then stop call rand ; Otherwise, get random value cpi MRATE ; Should we mutate this character? jnc mcloop ; If not, just copy next character call rndchr ; Otherwise, get a random character dcx h ; And store it instead of the character we had mov m,a inx h jmp mcloop ;;; Calculate fitness of candidate under [HL], fitness is ;;; returned in D. Fitness is "inverted", i.e. a fitness of 0 ;;; means everything matches. fitnes: lxi b,target lxi d,tgtsz ; E=counter, D=fitness floop: dcr e ; Done yet? rz ; If so, return. ldax b ; Get target character inx b cmp m ; Compare to current character inx h jz floop ; If they match, don't do anything inr d ; If they don't match, count this jmp floop ;;; Generate a random uppercase letter, or a space ;;; Return in A, other registers preserved rndchr: call rand ; Get a random value ani 31 ; from 0 to 31 cpi 28 ; If 28 or higher, jnc rndchr ; get another value adi 'A' ; Make uppercase letter cpi 'Z'+1 ; If the result is 'Z' or lower, rc ; then return it, mvi a,' ' ; otherwise return a space ret ;;; Load 4 bytes from [HL] and use them, plus A, as part of seed ;;; in [BC] seed: mvi e,4 ; 4 bytes sloop: xra m inx h dcr e jnz sloop stax b inx b ret ;;; Random number generator using XABC algorithm rand: push h lxi h,rnddat inr m ; X++ mov a,m ; X inx h xra m ; ^ C inx h xra m ; ^ A mov m,a ; -> A inx h add m ; + B mov m,a ; -> B rar ; >>1 (ish) dcx h xra m ; ^ A dcx h add m ; + C mov m,a ; -> C pop h ret ;;; Print string to console using CP/M, saving all registers puts: push h push d push b push psw mvi c,9 ; CP/M print string call 5 lxi d,nl ; Print a newline as well mvi c,9 call 5 pop b pop d pop h pop psw ret nl: db 13,10,'$' target: db 'METHINKS IT IS LIKE A WEASEL$' tgtsz: equ $-target rnddat: ds 4 ; RNG state copies: ds 1 ; Copies left to make maxfit: ds 1 ; Best fitness seen maxptr: ds 2 ; Pointer to copy with best fitness parent: equ $ ; Store current parent here kids: equ $+tgtsz ; Store mutated copies here</lang>
- Output:
BEFHWYJNLPTBQDG KAULUCAHZC S BEFHWYJNZPTBQDG OAULUCOHAK S BEFHWYJNEPTMQDG OYULUCSHAKML HEFHWESNEPTMQDG IYULU SHAKML HETHWESMEPTMQDB IYULU SHAKML HETHWESMEPTLQEB IYU U XHAHML HETHWESMEPTLQEB IYE U XHAHML HETHWNSMEPTDQEB IYE U XHAPML HETHWNSSEPTKQAB IYE U XHAPML HEUHWNSSEPT IAW IKU U XHAPML HEUHWNSSEPT IAW IKU U OHAPML ... METHINKZ IT IS LRKE A WEASEL METHINKZ IT IS LIKE A WEASEL METHINKZ IT IS LIKE A WEASEL METHINKZ IT IS LIKE A WEASEL METHINKZ IT IS LIKE A WEASEL METHINKV IT IS LIKE A WEASEL METHINKV IT IS LIKE A WEASEL METHINKV IT IS LIKE A WEASEL METHINKV IT IS LIKE A WEASEL METHINKS IT IS LIKE A WEASEL
8086 Assembly
<lang asm> bits 16 cpu 8086 MRATE: equ 26 ; Mutation rate (MRATE/256) COPIES: equ 100 ; Amount of copies to make gettim: equ 02Ch ; MS-DOS get time function pstr: equ 9 ; MS-DOS print string section .text org 100h ;;; Use MS-DOS time to set random seed mov ah,gettim int 21h mov [rnddat],cx mov [rnddat+2],dx ;;; Make first parent (random characters) mov di,parent mov cx,target.size-1 getchr: call rndchr ; Get random character stosb ; Store in parent loop getchr mov al,'$' ; Write string terminator stosb ;;; Main loop. loop: mov bx,parent ; Print current parent mov dx,bx call puts call fitnes ; Check fitness test cl,cl ; If zero, we're done jnz nxmut ; If not, do another mutation ret ; Quit to DOS nxmut: mov dl,0FFh ; DL = best fitness yet mov di,kids ; Set DI to start of memory for children mov ch,COPIES ; CH = amount of copies to make xor bp,bp ;;; Make copy, mutate, and test fitness copy: mov bx,di ; Let BX = where next copy will go call mutcpy ; Make the copy (and adjust DI) call fitnes ; Check fitness cmp cl,dl ; Is it better than the previous best one? ja next ; If not, just do the next one, mov dl,cl ; Otherwise, this is now the best one lea bp,[di-target.size] ; Store a pointer to it in BP next: dec ch ; One copy less jnz copy ; Make another copy if we need to mov si,bp ; We're done, the best child becomes mov di,parent ; the parent for the next generation mov cx,target.size rep movsb jmp loop ; Next generation ;;; Make copy of parent, mutating as we go, and store at [DI] mutcpy: mov si,parent .loop: lodsb ; Get byte from parent stosb ; Store in copy cmp al,'$' ; Is it '$'? je .out ; Then we're done call rand ; Otherwise, should we mutate? cmp al,MRATE ja .loop ; If not, do next character call rndchr ; But if so, get random character, mov [di-1],al ; and overwrite the current character. jmp .loop ; Then do the next character. .out: ret ;;; Get fitness of character in [BX] fitnes: mov si,target xor cl,cl ; Fitness .loop: lodsb ; Get target character cmp al,'$' ; Done? je .out ; Then stop cmp al,[bx] ; Equal to character under [BX]? lahf ; Keep flags inc bx ; Increment BX sahf ; Restore flags (was al=[bx]?) je .loop ; If equal, do next character inc cx ; Otherwise, count this as a mismatch jmp .loop .out: ret ;;; Generate random character, [A-Z] or space. rndchr: call rand ; Get random number and al,31 ; Lower five bits cmp al,27 ; One of 27 characters? jae rndchr ; If not, get new random number add al,'A' ; Make uppercase letter cmp al,'Z' ; More than 'Z'? jbe .out ; If not, it's OK mov al,' ' ; Otherwise, give a space .out: ret ;;; Random number generator using XABC algorithm ;;; Returns random byte in AL rand: push cx push dx mov cx,[rnddat] ; CH=X CL=A mov dx,[rnddat+2] ; DH=B DL=C inc ch ; X++ xor cl,ch ; A ^= X xor cl,dl ; A ^= C add dh,cl ; B += A mov al,dh ; C' = B shr al,1 ; C' >>= 1 xor al,cl ; C' ^= A add al,dl ; C' += C mov dl,al ; C = C' mov [rnddat],cx mov [rnddat+2],dx pop dx pop cx ret ;;; Print string in DX, plus a newline, saving registers puts: push ax push dx mov ah,pstr int 21h mov dx,nl int 21h pop dx pop ax ret section .data nl: db 13,10,'$' target: db 'METHINKS IT IS LIKE A WEASEL$' .size: equ $-target section .bss rnddat: resb 4 ; RNG state parent: resb target.size ; Place to store current parent kids: resb COPIES*target.size ; Place to store children</lang>
- Output:
HIIBZTIDHHEFZMUEDCXQRUH GNXK HIIBRTODHHE ZMUEDCXQAUHIONXK HECBRYCDHHE ZMUEBCXQAMHIONXK HECBRYCDYHE UMUEBCE AMHIONXK HECBRNCDYHE DMUEBCE AMHIONXK HECHRNCDYHE DMUEBCE AMHIONXK HECHRNKDYHE DMUEJCE AMHIOKXK HECHRNKDWHE DMUEJCE AMHIOKXK HELHRNKSWHE DMUEJCE AMHIOYXK HELHVNKSWHE DM EJRE ABHIAYXK ... METHINKS JT IS LIKU A WEASEL METHINKS JT IS LIKU A WEASEL METHINKS JT IS LIKU A WEASEL METHINKS IT IS LIKU A WEASEL METHINKS IT IS LIKU A WEASEL METHINKS IT IS LIKU A WEASEL METHINKS IT IS LIKU A WEASEL METHINKS IT IS LIKU A WEASEL METHINKS IT IS LIKU A WEASEL METHINKS IT IS LIKE A WEASEL
8th
<lang forth> \ RosettaCode challenge http://rosettacode.org/wiki/Evolutionary_algorithm \ Responding to the criticism that the implementation was too directed, this \ version does a completely random selection of chars to mutate
var gen \ Convert a string of valid chars into an array of char-strings: "ABCDEFGHIJKLMNOPQRSTUVWXYZ " null s:/ var, valid-chars
\ How many mutations each generation will handle; the larger, the slower each \ generation but the fewer generations required: 300 var, #mutations 23 var, mutability
- get-random-char
valid-chars @ 27 rand-pcg n:abs swap n:mod a:@ nip ;
- mutate-string \ s -- s'
(
rand-pcg mutability @ n:mod not if
drop get-random-char
then
) s:map ;
- mutate \ s n -- a
\ iterate 'n' times over the initial string, mutating it each time \ save the original string, as the best of the previous generation: >r [] over a:push swap ( tuck mutate-string a:push swap ) r> times drop ;
\ compute Hamming distance of two strings:
- hamming \ s1 s2 -- n
0 >r s:len n:1- ( 2 pick over s:@ nip 2 pick rot s:@ nip n:- n:abs r> n:+ >r ) 0 rot loop 2drop r> ;
var best
- fitness-check \ s a -- s t
10000 >r
-1 best !
(
\ ix s ix s'
2 pick hamming
r@
over n:> if
rdrop >r
best !
else
2drop
then
)
a:each
rdrop best @ a:@ nip ;
- add-random-char \ s -- s'
get-random-char s:+ ;
\ take the target and make a random string of the same length
- initial-string \ s -- s
s:len "" swap ' add-random-char swap times ;
- done? \ s1 s2 -- s1 s2 | bye
2dup s:= if "Done in " . gen @ . " generations" . cr ;;; then ;
- setup-random
rand rand rand-pcg-seed ;
- evolve
1 gen n:+! \ create an array of #mutations strings mutated from the random string, drop the random #mutations @ mutate \ iterate over the array and pick the closest fit: fitness-check \ show this generation's best match: dup . cr \ check for end condition and continue if not done: done? evolve ;
"METHINKS IT IS LIKE A WEASEL" setup-random initial-string evolve bye</lang>
The output:
PIQSLOGHISTIPSDLZFGRDBYUCADA PIQSNOGH SQIPSDLZFGRDBYUEADA PIQSNOGH SQIPSDLZFG DBYUEDDA ... METHINKS IT IS LIKD A WEASEL METHINKS IT IS LIKD A WEASEL METHINKS IT IS LIKE A WEASEL Done in 43 generations
Ada
Very simple fitness determination. For testing purposes you can add a static seed value to the RNG initializations (sample output uses '12345' for both).
<lang Ada>with Ada.Text_IO; with Ada.Numerics.Discrete_Random; with Ada.Numerics.Float_Random; with Ada.Strings.Fixed; with Ada.Strings.Maps;
procedure Evolution is
-- only upper case characters allowed, and space, which uses '@' in -- internal representation (allowing subtype of Character). subtype DNA_Char is Character range '@' .. 'Z';
-- DNA string is as long as target string. subtype DNA_String is String (1 .. 28);
-- target string translated to DNA_Char string Target : constant DNA_String := "METHINKS@IT@IS@LIKE@A@WEASEL";
-- calculate the 'closeness' to the target DNA.
-- it returns a number >= 0 that describes how many chars are correct.
-- can be improved much to make evolution better, but keep simple for
-- this example.
function Fitness (DNA : DNA_String) return Natural is
Result : Natural := 0;
begin
for Position in DNA'Range loop
if DNA (Position) = Target (Position) then
Result := Result + 1;
end if;
end loop;
return Result;
end Fitness;
-- output the DNA using the mapping
procedure Output_DNA (DNA : DNA_String; Prefix : String := "") is
use Ada.Strings.Maps;
Output_Map : Character_Mapping;
begin
Output_Map := To_Mapping
(From => To_Sequence (To_Set (('@'))),
To => To_Sequence (To_Set ((' '))));
Ada.Text_IO.Put (Prefix);
Ada.Text_IO.Put (Ada.Strings.Fixed.Translate (DNA, Output_Map));
Ada.Text_IO.Put_Line (", fitness: " & Integer'Image (Fitness (DNA)));
end Output_DNA;
-- DNA_Char is a discrete type, use Ada RNG package Random_Char is new Ada.Numerics.Discrete_Random (DNA_Char); DNA_Generator : Random_Char.Generator;
-- need generator for floating type, too Float_Generator : Ada.Numerics.Float_Random.Generator;
-- returns a mutated copy of the parent, applying the given mutation rate
function Mutate (Parent : DNA_String;
Mutation_Rate : Float)
return DNA_String
is
Result : DNA_String := Parent;
begin
for Position in Result'Range loop
if Ada.Numerics.Float_Random.Random (Float_Generator) <= Mutation_Rate
then
Result (Position) := Random_Char.Random (DNA_Generator);
end if;
end loop;
return Result;
end Mutate;
-- genetic algorithm to evolve the string
-- could be made a function returning the final string
procedure Evolve (Child_Count : Positive := 100;
Mutation_Rate : Float := 0.2)
is
type Child_Array is array (1 .. Child_Count) of DNA_String;
-- determine the fittest of the candidates
function Fittest (Candidates : Child_Array) return DNA_String is
The_Fittest : DNA_String := Candidates (1);
begin
for Candidate in Candidates'Range loop
if Fitness (Candidates (Candidate)) > Fitness (The_Fittest)
then
The_Fittest := Candidates (Candidate);
end if;
end loop;
return The_Fittest;
end Fittest;
Parent, Next_Parent : DNA_String;
Children : Child_Array;
Loop_Counter : Positive := 1;
begin
-- initialize Parent
for Position in Parent'Range loop
Parent (Position) := Random_Char.Random (DNA_Generator);
end loop;
Output_DNA (Parent, "First: ");
while Parent /= Target loop
-- mutation loop
for Child in Children'Range loop
Children (Child) := Mutate (Parent, Mutation_Rate);
end loop;
Next_Parent := Fittest (Children);
-- don't allow weaker children as the parent
if Fitness (Next_Parent) > Fitness (Parent) then
Parent := Next_Parent;
end if;
-- output every 20th generation
if Loop_Counter mod 20 = 0 then
Output_DNA (Parent, Integer'Image (Loop_Counter) & ": ");
end if;
Loop_Counter := Loop_Counter + 1;
end loop;
Output_DNA (Parent, "Final (" & Integer'Image (Loop_Counter) & "): ");
end Evolve;
begin
-- initialize the random number generators Random_Char.Reset (DNA_Generator); Ada.Numerics.Float_Random.Reset (Float_Generator); -- evolve! Evolve;
end Evolution;</lang>
sample output:
First: FCLYNZAOQ KBSZHJAKAWOSZKBOBT, fitness: 1 20: MKTHCPKS IT MSBBIKEVB SPASEH, fitness: 17 40: METHIDKS IT NS BIKE B OQASET, fitness: 21 60: METHIDKS IT NS BIKE B OQASET, fitness: 21 80: METHIDKS IT NS BIKE B OQASET, fitness: 21 100: METHIDKS IT VS BIKE B WQASEP, fitness: 22 120: METHIDKS IT VS BIKE B WQASEP, fitness: 22 140: METHIDKS ITBVS LIKE B WEASEP, fitness: 23 160: METHIDKS ITBVS LIKE B WEASEP, fitness: 23 180: METHIDKS ITBVS LIKE B WEASEP, fitness: 23 200: METHIDKS ITBIS LIKE B WEASEP, fitness: 24 220: METHITKS ITBIS LIKE B WEASEL, fitness: 25 240: METHITKS ITBIS LIKE B WEASEL, fitness: 25 260: METHITKS ITBIS LIKE B WEASEL, fitness: 25 280: METHITKS ITBIS LIKE B WEASEL, fitness: 25 300: METHITKS ITBIS LIKE B WEASEL, fitness: 25 320: METHITKS ITBIS LIKE B WEASEL, fitness: 25 340: METHITKS ITBIS LIKE B WEASEL, fitness: 25 360: METHITKS ITBIS LIKE B WEASEL, fitness: 25 380: METHINKS ITBIS LIKE A WEASEL, fitness: 27 Final ( 384): METHINKS IT IS LIKE A WEASEL, fitness: 28
Aime
<lang aime>integer fitness(data t, data b) {
integer c, f, i;
f = 0;
for (i, c in b) {
f += sign(t[i] ^ c);
}
f;
}
void mutate(data e, data b, data u) {
integer c;
for (, c in b) {
e.append(drand(15) ? c : u[drand(26)]);
}
}
integer main(void) {
data b, t, u; integer f, i;
t = "METHINK IT IS LIKE A WEASEL"; u = "ABCDEFGHIJKLMNOPQRSTUVWXYZ ";
i = ~t;
while (i) {
i -= 1;
b.append(u[drand(26)]);
}
f = fitness(t, b);
while (f) {
data n;
integer a;
o_form("/lw4/~\n", f, b);
n = b;
i = 32;
while (i) {
data c;
i -= 1;
mutate(c, b, u);
a = fitness(t, c);
if (a < f) {
f = a;
n = c;
}
}
b = n; }
o_form("/lw4/~\n", f, b);
return 0;
}</lang>
- Output:
23 EAAXIZJROVOHSKREBNSAFHEKF B 22 EAUHIZJREVOHSKREBNSAFHEKF B 21 IAUHIZJREVOHSKREBESAFHEKF B 20 IKUHIZJRETOTSKREBESAFHEKFWB 20 IKUHIZJRETOTSKREBESAFHEKFWB 19 IKUHIZJRET USKREBESAFHEKFWA 19 IKUHIZJRET USKREBESAFHEKFWA 19 IKUHIZJRET USKREBESAFHEKFWA 18 IKUHIZJRET US REBESAFHEKFWA 18 IKUHIZJRET US REBESAFHEKFWA 17 IKMHIZJKET US REBESA HEKFWA 16 IKMHIZJKET US LEBEJA HEKJWA 16 IKMHIZJKET US LEBEJA HEKJWA 16 IKMHIZJKET US LEBEJA HEKJWA 16 IKMHIZJKET US LEBEJA HEKJWA 15 MKKHIZJ ET US LEBEJF HEKJWA 14 MEEHIZJ ET US LEBEJF HEKJWA 14 MEEHIZJ ET US LEBEJF HEKJWA 13 MEEHIZJ ET US LKBE F OEKJWA 12 MEEHIZJ ET US LKKE F OEKJWA 12 MEEHIZJ ET US LKKE F OEKJWA 11 MEEHIZJ ET US LIKE F OEKJWA 11 MEEHIZJ ET US LIKE F OEKJWA 10 MEEHIZJ IT US LIKE F OEKJWA 10 MEEHIZJ IT US LIKE F OEKJWA ... 1 METHINK IT IS LIKE F WEASEL 1 METHINK IT IS LIKE F WEASEL 0 METHINK IT IS LIKE A WEASEL
ALGOL 68
Note: This specimen retains the original C coding style.
<lang algol68>STRING target := "METHINKS IT IS LIKE A WEASEL";
PROC fitness = (STRING tstrg)REAL: (
INT sum := 0;
FOR i FROM LWB tstrg TO UPB tstrg DO
sum +:= ABS(ABS target[i] - ABS tstrg[i])
OD;
# fitness := # 100.0*exp(-sum/10.0)
);
PROC rand char = CHAR: (
#STATIC# []CHAR ucchars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ "; # rand char := # ucchars[ENTIER (random*UPB ucchars)+1]
);
PROC mutate = (REF STRING kid, parent, REAL mutate rate)VOID: (
FOR i FROM LWB parent TO UPB parent DO
kid[i] := IF random < mutate rate THEN rand char ELSE parent[i] FI
OD
);
PROC kewe = ( STRING parent, INT iters, REAL fits, REAL mrate)VOID: (
printf(($"#"4d" fitness: "g(-6,2)"% "g(-6,4)" '"g"'"l$, iters, fits, mrate, parent))
);
PROC evolve = VOID: (
FLEX[UPB target]CHAR parent;
REAL fits;
[100]FLEX[UPB target]CHAR kid;
INT iters := 0;
kid[LWB kid] := LOC[UPB target]CHAR;
REAL mutate rate;
# initialize #
FOR i FROM LWB parent TO UPB parent DO
parent[i] := rand char
OD;
fits := fitness(parent);
WHILE fits < 100.0 DO
INT j;
REAL kf;
mutate rate := 1.0 - exp(- (100.0 - fits)/400.0);
FOR j FROM LWB kid TO UPB kid DO
mutate(kid[j], parent, mutate rate)
OD;
FOR j FROM LWB kid TO UPB kid DO
kf := fitness(kid[j]);
IF fits < kf THEN
fits := kf;
parent := kid[j]
FI
OD;
IF iters MOD 100 = 0 THEN
kewe( parent, iters, fits, mutate rate )
FI;
iters+:=1
OD;
kewe( parent, iters, fits, mutate rate )
);
main: (
evolve
)</lang> Sample output:
#0000 fitness: 0.00% 0.2212 'JUQBKWCHNPJ LO LFDKHDJJNQIFQ' #0100 fitness: 5.50% 0.2104 'NGVGIOJV IT JS MGLD C VEAWCI' #0200 fitness: 22.31% 0.1765 'MGTGIOJS IU JS MGKD C VEAREL' #0300 fitness: 60.65% 0.0937 'METHIOKS IU IS LIKE B VFASEL' #0354 fitness: 100.00% 0.0235 'METHINKS IT IS LIKE A WEASEL'
Amstrad CPC Locomotive BASIC
Finding the target string on an Amstrad CPC takes a bit less than 45 minutes.
<lang locobasic>10 s$="METHINKS IT IS LIKE A WEASEL" 20 cc=100 30 prop=0.05 40 sl=len(s$) 50 dim c(cc,sl) 60 dim o(sl) 70 dim v(cc) 80 cp = 1 90 start=time 100 for i=1 to sl 110 o(i)=asc(mid$(s$,i,1)) 120 if o(i)=32 then o(i)=64 130 next 140 for j=1 to sl:c(1,j)=int(64+27*rnd(1)):next 150 for i=2 to cc 160 for j=1 to sl:c(i,j)=c(cp,j):next 170 next 180 for i=1 to cc 190 for j=1 to sl 200 if rnd(1)>prop then goto 220 210 c(i,j)=int(64+27*rnd(1)) 220 next j: next i 230 sc=0:bsi=1 240 for i=1 to cc 250 v(i)=0 260 for j=1 to sl 270 if c(i,j)=o(j) then v(i)=v(i)+1 280 next j 290 if v(i)>sc then sc=v(i):bsi=i 300 next i 310 print sc"@"bsi;:if bsi<10 then print " "; 320 for i=1 to sl:?chr$(c(bsi, i)+(c(bsi, i)=64)*32);:next:? 330 if sc=sl then print "We have a weasel!":? "Time: "(time-start)/300:end 340 cp=bsi 350 goto 150</lang>
Output during calculation (excerpt):
27 @ 10 METHINKGS IT IS LQKE A WEASEL 27 @ 9 METHINKGS IT IS LYKE A WEASEL 27 @ 2 METHINKGS IT IS LYKE A WEASEL 27 @ 2 METHINKGS IT IS LYKE A WEASEL 27 @ 7 METHINKGS IT IS LYKE A WEASEL 27 @ 2 METHINKGS IT IS LYKE A WEASEL 28 @ 93 METHINKGS IT IS LIKE A WEASEL We have a weasel! Time: 2572.87
APL
<lang APL> evolve←{
⍺←0.1
target←'METHINKS IT IS LIKE A WEASEL'
charset←27↑⎕A
fitness←{target+.=⍵}
mutate←⍺∘{
(⍺>?(⍴target)/0){
⍺:(?⍴charset)⊃charset
⍵
}¨⍵
}
⍵{
target≡⎕←⍵:⍵
next←mutate¨⍺/⊂⍵
⍺∇(⊃⍒fitness¨next)⊃next
}charset[?(⍴target)/⍴charset]
}
</lang>
- Output:
evolve 100 JDBBTX JVAWZVJUUGACMOMZEATQH JEBITX JVAWZVJUUGACMOMWEATQH JEBGTX JVAWZVJ UGACMORWEATQH JEHGTX JVAW VJ UGACMOJWEATQH JEHGTX JVAW VJ UGACMAJWEATQH IEHGTX JFAR VJ EGACMAJWEATEH IEHGTX JFAR VJ LGACMAJWEATEH IEHGTX FKAR IJ LGACMAJWEATEH IEJGTX FKAT IJ LGACMAJWEATEW MEJGTX FKAT IJ LGACKAJWEATEW MERGTX F AT IJ LGACKAJWEATEW ... METHI KS IT IS LIKE A WEASEL METHINKS IT IS LIKE A WPASEL METHINKS IT IS LIKE A WPASEL METHINKS IT IS LIKE A WPASEL METHINKS IT IS LIKE A WPASEL METHINKS IT IS LIKE A WPASEL METHINKS IT IS LIKE A WPASEL METHINKS IT IS LIKE A WPASEL METHINKS IT IS LIKE A WJASEL METHINKS IT IS LIKE A WEASEL METHINKS IT IS LIKE A WEASEL
AutoHotkey
<lang AutoHotkey>output := "" target := "METHINKS IT IS LIKE A WEASEL" targetLen := StrLen(target) Loop, 26 possibilities_%A_Index% := Chr(A_Index+64) ; A-Z possibilities_27 := " " C := 100
parent := "" Loop, %targetLen% { Random, randomNum, 1, 27
parent .= possibilities_%randomNum%
}
Loop, { If (target = parent) Break If (Mod(A_Index,10) = 0) output .= A_Index ": " parent ", fitness: " fitness(parent, target) "`n" bestFit := 0 Loop, %C% If ((fitness := fitness(spawn := mutate(parent), target)) > bestFit) bestSpawn := spawn , bestFit := fitness parent := bestFit > fitness(parent, target) ? bestSpawn : parent iter := A_Index } output .= parent ", " iter MsgBox, % output ExitApp
mutate(parent) { local output, replaceChar, newChar output := "" Loop, %targetLen% { Random, replaceChar, 0, 9 If (replaceChar != 0) output .= SubStr(parent, A_Index, 1) else { Random, newChar, 1, 27 output .= possibilities_%newChar% } } Return output }
fitness(string, target) { totalFit := 0 Loop, % StrLen(string) If (SubStr(string, A_Index, 1) = SubStr(target, A_Index, 1)) totalFit++ Return totalFit }</lang> Output:
10: DETRNNKR IAQPFLNVKZ AMXEASEL, fitness: 14 20: METKNNKS IL PALLKKE A XEASEL, fitness: 20 30: METHGNKS IT PSXLKKE A XEASEL, fitness: 23 40: METHGNKS IT IS LKKE A EEASEL, fitness: 25 50: METHGNKS IT IS LKKE A WEASEL, fitness: 26 60: METHGNKS IT IS LKKE A WEASEL, fitness: 26 70: METHGNKS IT IS LIKE A WEASEL, fitness: 27 METHINKS IT IS LIKE A WEASEL, 72
AWK
I apply the rate to each character in each generated child. The number of generations required seems to be really sensitive to the rate. I used the default seeding in GNU awk to obtain the results below. I suspect the algorithm used to generate the pseudo-random numbers may also influence the rapidity of convergence but I haven't investigated that yet. The output shown was obtained using GNU Awk 3.1.5. BusyBox v1.20.0.git also works but using the same rate generates 88 generations before converging. <lang awk>
- !/bin/awk -f
function randchar(){ return substr(charset,randint(length(charset)+1),1) } function mutate(gene,rate ,l,newgene){ newgene = "" for (l=1; l < 1+length(gene); l++){ if (rand() < rate)
newgene = newgene randchar()
else
newgene = newgene substr(gene,l,1)
} return newgene } function fitness(gene,target ,k,fit){ fit = 0 for (k=1;k<1+length(gene);k++){ if (substr(gene,k,1) == substr(target,k,1)) fit = fit + 1 } return fit } function randint(n){ return int(n * rand()) } function evolve(){
maxfit = fitness(parent,target)
oldfit = maxfit
maxj = 0
for (j=1; j < D; j++){
child[j] = mutate(parent,mutrate)
fit[j] = fitness(child[j],target)
if (fit[j] > maxfit) {
maxfit = fit[j]
maxj = j
}
}
if (maxfit > oldfit) parent = child[maxj]
}
BEGIN{ target = "METHINKS IT IS LIKE A WEASEL" charset = " ABCDEFGHIJKLMNOPQRSTUVWXYZ" mutrate = 0.10 if (ARGC > 1) mutrate = ARGV[1] lenset = length(charset) C = 100 D = C + 1 parent = "" for (j=1; j < length(target)+1; j++) {
parent = parent randchar()
}
print "target: " target print "fitness of target: " fitness(target,target) print "initial parent: " parent gens = 0 while (parent != target){
evolve()
gens = gens + 1
if (gens % 10 == 0) print "after " gens " generations,","new parent: " parent," with fitness: " fitness(parent,target)
}
print "after " gens " generations,"," evolved parent: " parent }
</lang> Output:
# ./awkevolution .08998 target: METHINKS IT IS LIKE A WEASEL fitness of target: 28 initial parent: EGVCODUCLCILXFXEPNHAMNV BP S after 10 generations, new parent: EGTSIDKS IT XFXXIKHAANUDEW S with fitness: 11 after 20 generations, new parent: MKTIIDKS IT IF XIKB A WEEWEL with fitness: 20 after 30 generations, new parent: M TIIDKS IT IF LIKE A WENSEL with fitness: 23 after 40 generations, new parent: METIIDKS IT IF LIKE A WEASEL with fitness: 25 after 50 generations, new parent: METHIDKS IT IS LIKE A WEASEL with fitness: 27 after 60 generations, new parent: METHINKS IT IS LIKE A WEASEL with fitness: 28 after 60 generations, evolved parent: METHINKS IT IS LIKE A WEASEL #
Batch File
<lang dos> @echo off setlocal enabledelayedexpansion
set target=M E T H I N K S @ I T @ I S @ L I K E @ A @ W E A S E L set chars=A B C D E F G H I J K L M N O P Q R S T U V W X Y Z @
set tempcount=0 for %%i in (%target%) do (
set /a tempcount+=1 set target!tempcount!=%%i
) call:parent
echo %target% echo --------------------------------------------------------
- loop
call:fitness parent set currentfit=%errorlevel% if %currentfit%==28 goto end echo %parent% - %currentfit% [%attempts%] set attempts=0
- innerloop
set /a attempts+=1 title Attemps - %attempts% call:mutate %parent% call:fitness tempparent set newfit=%errorlevel% if %newfit% gtr %currentfit% (
set tempcount=0 set "parent=" for %%i in (%tempparent%) do ( set /a tempcount+=1 set parent!tempcount!=%%i set parent=!parent! %%i ) goto loop
) goto innerloop
- end
echo %parent% - %currentfit% [%attempts%] echo Done. exit /b
- parent
set "parent=" for /l %%i in (1,1,28) do (
set /a charchosen=!random! %% 27 + 1
set tempcount=0
for %%j in (%chars%) do (
set /a tempcount+=1
if !charchosen!==!tempcount! (
set parent%%i=%%j
set parent=!parent! %%j
)
)
) exit /b
- fitness
set fitness=0 set array=%1 for /l %%i in (1,1,28) do if !%array%%%i!==!target%%i! set /a fitness+=1 exit /b %fitness%
- mutate
set tempcount=0 set returnarray=tempparent set "%returnarray%=" for %%i in (%*) do (
set /a tempcount+=1 set %returnarray%!tempcount!=%%i set %returnarray%=!%returnarray%! %%i
) set /a tomutate=%random% %% 28 + 1 set /a mutateto=%random% %% 27 + 1 set tempcount=0 for %%i in (%chars%) do (
set /a tempcount+=1 if %mutateto%==!tempcount! ( set %returnarray%!tomutate!=%%i )
) set "%returnarray%=" for /l %%i in (1,1,28) do set %returnarray%=!%returnarray%! !%returnarray%%%i! exit /b </lang>
- Output:
Sample Output:
M E T H I N K S @ I T @ I S @ L I K E @ A @ W E A S E L -------------------------------------------------------- R S T L U M F Q Y B T L G P L Q T B F C B X F S X S H Y - 3 [] R S T L I M F Q Y B T L G P L Q T B F C B X F S X S H Y - 4 [9] R S T L I M F Q Y B T L G S L Q T B F C B X F S X S H Y - 5 [49] R E T L I M F Q Y B T L G S L Q T B F C B X F S X S H Y - 6 [2] R E T L I M F Q Y B T L G S L Q T B F C B X F S X S H L - 7 [18] R E T L I M F Q Y B T L G S L Q T B F C B X W S X S H L - 8 [5] R E T L I M F Q Y B T @ G S L Q T B F C B X W S X S H L - 9 [13] R E T L I M F Q Y B T @ G S L L T B F C B X W S X S H L - 10 [114] R E T L I M K Q Y B T @ G S L L T B F C B X W S X S H L - 11 [9] R E T L I M K Q Y B T @ G S @ L T B F C B X W S X S H L - 12 [17] R E T L I M K S Y B T @ G S @ L T B F C B X W S X S H L - 13 [53] R E T L I M K S Y I T @ G S @ L T B F C B X W S X S H L - 14 [20] R E T L I M K S @ I T @ G S @ L T B F C B X W S X S H L - 15 [121] R E T L I M K S @ I T @ G S @ L T B F C B X W S X S E L - 16 [86] R E T L I M K S @ I T @ G S @ L T B F C B X W E X S E L - 17 [115] R E T H I M K S @ I T @ G S @ L T B F C B X W E X S E L - 18 [54] R E T H I M K S @ I T @ G S @ L T B F @ B X W E X S E L - 19 [121] R E T H I M K S @ I T @ G S @ L T B F @ B X W E A S E L - 20 [207] M E T H I M K S @ I T @ G S @ L T B F @ B X W E A S E L - 21 [5] M E T H I M K S @ I T @ G S @ L I B F @ B X W E A S E L - 22 [163] M E T H I M K S @ I T @ G S @ L I B E @ B X W E A S E L - 23 [84] M E T H I M K S @ I T @ G S @ L I K E @ B X W E A S E L - 24 [31] M E T H I N K S @ I T @ G S @ L I K E @ B X W E A S E L - 25 [432] M E T H I N K S @ I T @ I S @ L I K E @ B X W E A S E L - 26 [85] M E T H I N K S @ I T @ I S @ L I K E @ A X W E A S E L - 27 [144] M E T H I N K S @ I T @ I S @ L I K E @ A @ W E A S E L - 28 [227] Done.
BBC BASIC
<lang bbcbasic> target$ = "METHINKS IT IS LIKE A WEASEL"
parent$ = "IU RFSGJABGOLYWF XSMFXNIABKT"
mutation_rate = 0.5
children% = 10
DIM child$(children%)
REPEAT
bestfitness = 0
bestindex% = 0
FOR index% = 1 TO children%
child$(index%) = FNmutate(parent$, mutation_rate)
fitness = FNfitness(target$, child$(index%))
IF fitness > bestfitness THEN
bestfitness = fitness
bestindex% = index%
ENDIF
NEXT index%
parent$ = child$(bestindex%)
PRINT parent$
UNTIL parent$ = target$
END
DEF FNfitness(text$, ref$)
LOCAL I%, F%
FOR I% = 1 TO LEN(text$)
IF MID$(text$, I%, 1) = MID$(ref$, I%, 1) THEN F% += 1
NEXT
= F% / LEN(text$)
DEF FNmutate(text$, rate)
LOCAL C%
IF rate > RND(1) THEN
C% = 63+RND(27)
IF C% = 64 C% = 32
MID$(text$, RND(LEN(text$)), 1) = CHR$(C%)
ENDIF
= text$</lang>
C
<lang c>#include <stdio.h>
- include <stdlib.h>
- include <string.h>
const char target[] = "METHINKS IT IS LIKE A WEASEL"; const char tbl[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ ";
- define CHOICE (sizeof(tbl) - 1)
- define MUTATE 15
- define COPIES 30
/* returns random integer from 0 to n - 1 */ int irand(int n) { int r, rand_max = RAND_MAX - (RAND_MAX % n); while((r = rand()) >= rand_max); return r / (rand_max / n); }
/* number of different chars between a and b */ int unfitness(const char *a, const char *b) { int i, sum = 0; for (i = 0; a[i]; i++) sum += (a[i] != b[i]); return sum; }
/* each char of b has 1/MUTATE chance of differing from a */ void mutate(const char *a, char *b) { int i; for (i = 0; a[i]; i++) b[i] = irand(MUTATE) ? a[i] : tbl[irand(CHOICE)];
b[i] = '\0'; }
int main() { int i, best_i, unfit, best, iters = 0; char specimen[COPIES][sizeof(target) / sizeof(char)];
/* init rand string */ for (i = 0; target[i]; i++) specimen[0][i] = tbl[irand(CHOICE)]; specimen[0][i] = 0;
do { for (i = 1; i < COPIES; i++) mutate(specimen[0], specimen[i]);
/* find best fitting string */ for (best_i = i = 0; i < COPIES; i++) { unfit = unfitness(target, specimen[i]); if(unfit < best || !i) { best = unfit; best_i = i; } }
if (best_i) strcpy(specimen[0], specimen[best_i]); printf("iter %d, score %d: %s\n", iters++, best, specimen[0]); } while (best);
return 0; }</lang>output<lang>iter 0, score 26: WKVVYFJUHOMQJNZYRTEQAGDVXKYC iter 1, score 25: WKVVTFJUHOMQJN YRTEQAGDVSKXC iter 2, score 25: WKVVTFJUHOMQJN YRTEQAGDVSKXC iter 3, score 24: WKVVTFJUHOMQJN YRTEQAGDVAKFC ... iter 221, score 1: METHINKSHIT IS LIKE A WEASEL iter 222, score 1: METHINKSHIT IS LIKE A WEASEL iter 223, score 0: METHINKS IT IS LIKE A WEASEL</lang>
C#
<lang csharp>using System; using System.Collections.Generic; using System.Linq;
static class Program {
static Random Rng = new Random((int)DateTime.Now.Ticks);
static char NextCharacter(this Random self) {
const string AllowedChars = " ABCDEFGHIJKLMNOPQRSTUVWXYZ";
return AllowedChars[self.Next() % AllowedChars.Length];
}
static string NextString(this Random self, int length) {
return String.Join("", Enumerable.Repeat(' ', length)
.Select(c => Rng.NextCharacter()));
}
static int Fitness(string target, string current) {
return target.Zip(current, (a, b) => a == b ? 1 : 0).Sum();
}
static string Mutate(string current, double rate) {
return String.Join("", from c in current
select Rng.NextDouble() <= rate ? Rng.NextCharacter() : c);
}
static void Main(string[] args) {
const string target = "METHINKS IT IS LIKE A WEASEL";
const int C = 100;
const double P = 0.05;
// Start with a random string the same length as the target.
string parent = Rng.NextString(target.Length);
Console.WriteLine("START: {0,20} fitness: {1}",
parent, Fitness(target, parent));
int i = 0;
while (parent != target) {
// Create C mutated strings + the current parent.
var candidates = Enumerable.Range(0, C + 1)
.Select(n => n > 0 ? Mutate(parent, P) : parent);
// select the fittest
parent = candidates.OrderByDescending(c => Fitness(target, c)).First();
++i;
Console.WriteLine(" #{0,6} {1,20} fitness: {2}",
i, parent, Fitness(target, parent));
}
Console.WriteLine("END: #{0,6} {1,20}", i, parent);
}
}</lang>
Example output:
START: PACQXJB CQPWEYKSVDCIOUPKUOJY fitness: 0
# 1 PALQXJB CQPWEYKSVDCIOUPEUOJY fitness: 1
# 2 PALQXJB CQPWEYKSVDEIOUPEUOJY fitness: 2
# 3 PALQXJB CQPWEYKSVDE OUPEUOJY fitness: 3
# 4 MALQOJB CQPWEYKSVDE OUPEUOJY fitness: 4
# 5 MALQOJB CQPWEYKSVKE OUPEUOJY fitness: 5
# 6 MALQOJB CQPWEYKLVKE OUPEUOES fitness: 7
# 7 MALQOJB CQPWEYKLVKE OUPEAOES fitness: 8
# 8 M LQOJB CQPWEYKLVKE OUPEAOES fitness: 8
# 9 M LQOJB CQPWEYKL KE OUPEAOES fitness: 8
# 10 M LHOJB CQPWEYKL KE OUPEAOES fitness: 9
# 11 M LHOJB CQPWEYKL KE OGYEAOEL fitness: 10
# 12 M LHOJB CQP EYKL KE OGYEAOEL fitness: 11
# 13 M THOJB CQP EYKL KE OGYEAOEL fitness: 12
# 14 M THOJB CQP ESKL KE OGYEAOEL fitness: 13
# 15 M THOJB CQP ESKL KE AGYEAOEL fitness: 14
# 16 M THHJBSCQP ESKL KE AGYEAOEL fitness: 15
# 17 M THHJBSCQP ES L KE AGYEAOEL fitness: 16
# 18 MXTHHJBSCQP ES L KE AGYEASEL fitness: 17
# 19 MXTHHJBSCOT ES L KE AGYEASEL fitness: 18
# 20 MXTHHJBSCOT ES L KE AGYEASEL fitness: 18
# 21 METHHJBSCOT GS L KE ACYEASEL fitness: 19
# 22 METHIJBSCOT GS L KE ACYEASEL fitness: 20
# 23 METHILBSCOT GS L KE ACYEASEL fitness: 20
# 24 METHILBSCOT GS L KE ACWEASEL fitness: 21
# 25 METHILBS OT GS LBKE ACWEASEL fitness: 22
# 26 METHILBS OT GS LBKE ACWEASEL fitness: 22
# 27 METHILBS OT IS LBKE ACWEASEL fitness: 23
# 28 METHILBS OT IS LBKE ACWEASEL fitness: 23
# 29 METHILBS OT IS LBKE ACWEASEL fitness: 23
# 30 METHILBS CT IS LPKE ACWEASEL fitness: 23
# 31 METHILBS CT IS LPKE ACWEASEL fitness: 23
# 32 METHILBS CT IS LPKE A WEASEL fitness: 24
# 33 METHILBS ET IS LPKE A WEASEL fitness: 24
# 34 METHILBS ET IS LPKE A WEASEL fitness: 24
# 35 METHILBS ET IS LPKE A WEASEL fitness: 24
# 36 METHILBS ET IS LPKE A WEASEL fitness: 24
# 37 METHILBS IT IS LPKE A WEASEL fitness: 25
# 38 METHILBS IT IS LPKE A WEASEL fitness: 25
# 39 METHILBS IT IS LPKE A WEASEL fitness: 25
# 40 METHILBS IT IS LPKE A WEASEL fitness: 25
# 41 METHILBS IT IS LPKE A WEASEL fitness: 25
# 42 METHILBS IT IS LPKE A WEASEL fitness: 25
# 43 METHINBS IT IS LPKE A WEASEL fitness: 26
# 44 METHINBS IT IS LPKE A WEASEL fitness: 26
# 45 METHINBS IT IS LPKE A WEASEL fitness: 26
# 46 METHINBS IT IS LIKE A WEASEL fitness: 27
# 47 METHINBS IT IS LIKE A WEASEL fitness: 27
# 48 METHINBS IT IS LIKE A WEASEL fitness: 27
# 49 METHINBS IT IS LIKE A WEASEL fitness: 27
# 50 METHINBS IT IS LIKE A WEASEL fitness: 27
# 51 METHINBS IT IS LIKE A WEASEL fitness: 27
# 52 METHINBS IT IS LIKE A WEASEL fitness: 27
# 53 METHINBS IT IS LIKE A WEASEL fitness: 27
# 54 METHINBS IT IS LIKE A WEASEL fitness: 27
# 55 METHINBS IT IS LIKE A WEASEL fitness: 27
# 56 METHINBS IT IS LIKE A WEASEL fitness: 27
# 57 METHINBS IT IS LIKE A WEASEL fitness: 27
# 58 METHINBS IT IS LIKE A WEASEL fitness: 27
# 59 METHINBS IT IS LIKE A WEASEL fitness: 27
# 60 METHINBS IT IS LIKE A WEASEL fitness: 27
# 61 METHINBS IT IS LIKE A WEASEL fitness: 27
# 62 METHINKS IT IS LIKE A WEASEL fitness: 28
END: # 62 METHINKS IT IS LIKE A WEASEL
C++
<lang cpp>#include <string>
- include <cstdlib>
- include <iostream>
- include <cassert>
- include <algorithm>
- include <vector>
- include <ctime>
std::string allowed_chars = " ABCDEFGHIJKLMNOPQRSTUVWXYZ";
// class selection contains the fitness function, encapsulates the // target string and allows access to it's length. The class is only // there for access control, therefore everything is static. The // string target isn't defined in the function because that way the // length couldn't be accessed outside. class selection { public:
// this function returns 0 for the destination string, and a
// negative fitness for a non-matching string. The fitness is
// calculated as the negated sum of the circular distances of the
// string letters with the destination letters.
static int fitness(std::string candidate)
{
assert(target.length() == candidate.length());
int fitness_so_far = 0;
for (int i = 0; i < target.length(); ++i)
{
int target_pos = allowed_chars.find(target[i]);
int candidate_pos = allowed_chars.find(candidate[i]);
int diff = std::abs(target_pos - candidate_pos);
fitness_so_far -= std::min(diff, int(allowed_chars.length()) - diff);
}
return fitness_so_far; }
// get the target string length
static int target_length() { return target.length(); }
private:
static std::string target;
};
std::string selection::target = "METHINKS IT IS LIKE A WEASEL";
// helper function: cyclically move a character through allowed_chars void move_char(char& c, int distance) {
while (distance < 0) distance += allowed_chars.length(); int char_pos = allowed_chars.find(c); c = allowed_chars[(char_pos + distance) % allowed_chars.length()];
}
// mutate the string by moving the characters by a small random // distance with the given probability std::string mutate(std::string parent, double mutation_rate) {
for (int i = 0; i < parent.length(); ++i)
if (std::rand()/(RAND_MAX + 1.0) < mutation_rate)
{
int distance = std::rand() % 3 + 1;
if(std::rand()%2 == 0)
move_char(parent[i], distance);
else
move_char(parent[i], -distance);
}
return parent;
}
// helper function: tell if the first argument is less fit than the // second bool less_fit(std::string const& s1, std::string const& s2) {
return selection::fitness(s1) < selection::fitness(s2);
}
int main() {
int const C = 100;
std::srand(time(0));
std::string parent;
for (int i = 0; i < selection::target_length(); ++i)
{
parent += allowed_chars[std::rand() % allowed_chars.length()];
}
int const initial_fitness = selection::fitness(parent);
for(int fitness = initial_fitness;
fitness < 0;
fitness = selection::fitness(parent))
{
std::cout << parent << ": " << fitness << "\n";
double const mutation_rate = 0.02 + (0.9*fitness)/initial_fitness;
std::vector<std::string> childs;
childs.reserve(C+1);
childs.push_back(parent);
for (int i = 0; i < C; ++i)
childs.push_back(mutate(parent, mutation_rate));
parent = *std::max_element(childs.begin(), childs.end(), less_fit); } std::cout << "final string: " << parent << "\n";
}</lang> Example output:
BBQYCNLDIHG RWEXN PNGFTCMS: -203 ECPZEOLCHFJBCXTXFYLZQPDDQ KP: -177 HBSBGMKEEIM BUTUGWKWNRCGSZNN: -150 EEUCGNKDCHN RSSITKZPRBESYQK: -134 GBRFGNKDAINX TVRITIZPSBERXTH: -129 JEUFILLDDGNZCWYRIWFWSUAERZUI: -120 JESGILIGDJOZCWXRIWFVSXZESXXI: -109 JCSHILIIDIOZCTZOIUIVVXZEUVXI: -93 KDSHHLJIDIOZER LIUGXVXXFWW I: -76 KDSHGNMIDIOZHR LIUHXWXWFWW L: -69 LDSHHNMLDIOZKR LGSEXWXWFYV L: -59 LDSHHNMNDIOYKU LGSEXY WFYV M: -55 LCSHHNMLDHR IT LGSEZY WFYSBM: -44 LCSHHNMNBIR IT LGSEZY WFASBM: -36 LCSHHNMQBIQ JT LGQEZY WFASBM: -33 LCSIHNMRBIS JT LGQE Y WFASBM: -30 LESIHNMSBIS JR LGQE Y WFASBM: -27 LESIJNMSBIS JR LHOE A WFASBM: -21 LERIJNJSBIS JR LHOF A WFASEM: -19 LERIJNJSBIS JR LHLF A WFASEM: -16 NERIJNJS IS JR LHLF A WFASEM: -14 NERIJNJS IS JS LHLF A WFASEM: -13 NERIJNKS IS JS LHLF A WFASEM: -12 NERIJNKS IS JS LHKF A WFASEM: -11 NERIJNKS IS JS LHKF A WFASEM: -11 NERIJNKS IS JS LHKF A WEASEM: -10 NERIJNKS IS JS LHKF A WEASEM: -10 NERIJNKS IS JS LHKF A WEASEL: -9 NERIJNKS IS JS LHKF A WEASEL: -9 NETIJNKS IS JS LHKF A WEASEL: -7 NETIJNKS IS JS LHKF A WEASEL: -7 NETIJNKS IT JS LHKF A WEASEL: -6 NETIINKS IT JS LHKF A WEASEL: -5 NETIINKS IT JS LHKE A WEASEL: -4 NETHINKS IT JS LHKE A WEASEL: -3 NETHINKS IT JS LIKE A WEASEL: -2 NETHINKS IT JS LIKE A WEASEL: -2 NETHINKS IT JS LIKE A WEASEL: -2 NETHINKS IT JS LIKE A WEASEL: -2 NETHINKS IT JS LIKE A WEASEL: -2 NETHINKS IT JS LIKE A WEASEL: -2 METHINKS IT JS LIKE A WEASEL: -1 METHINKS IT JS LIKE A WEASEL: -1 METHINKS IT JS LIKE A WEASEL: -1 final string: METHINKS IT IS LIKE A WEASEL
Ceylon
<lang ceylon>import ceylon.random {
DefaultRandom }
shared void run() {
value mutationRate = 0.05; value childrenPerGeneration = 100; value target = "METHINKS IT IS LIKE A WEASEL"; value alphabet = {' ', *('A'..'Z')}; value random = DefaultRandom();
value randomLetter => random.nextElement(alphabet);
function fitness(String a, String b) => count {for([c1, c2] in zipPairs(a, b)) c1 == c2};
function mutate(String string) => String { for(letter in string) if(random.nextFloat() < mutationRate) then randomLetter else letter };
function makeCopies(String string) => {for(i in 1..childrenPerGeneration) mutate(string)};
function chooseFittest(String+ children) => children .map((String element) => element->fitness(element, target)) .max(increasingItem) .key;
variable value parent = String {for(i in 1..target.size) randomLetter}; variable value generationCount = 0; function display() => print("``generationCount``: ``parent``");
display(); while(parent != target) { parent = chooseFittest(parent, *makeCopies(parent)); generationCount++; display(); }
print("mutated into target in ``generationCount`` generations!");
}</lang>
Clojure
Define the evolution parameters (values here per Wikipedia article), with a couple of problem constants. <lang clojure>(def c 100) ;number of children in each generation (def p 0.05) ;mutation probability
(def target "METHINKS IT IS LIKE A WEASEL") (def tsize (count target))
(def alphabet " ABCDEFGHIJLKLMNOPQRSTUVWXYZ")</lang> Now the major functions. fitness simply counts the number of characters matching the target. <lang clojure>(defn fitness [s] (count (filter true? (map = s target)))) (defn perfectly-fit? [s] (= (fitness s) tsize))
(defn randc [] (rand-nth alphabet)) (defn mutate [s] (map #(if (< (rand) p) (randc) %) s))</lang> Finally evolve. At each generation, print the generation number, the parent, and the parent's fitness. <lang clojure>(loop [generation 1, parent (repeatedly tsize randc)]
(println generation, (apply str parent), (fitness parent))
(if-not (perfectly-fit? parent)
(let [children (repeatedly c #(mutate parent))
fittest (apply max-key fitness parent children)]
(recur (inc generation), fittest))))</lang>
CLU
<lang clu>fitness = proc (s, t: string) returns (int)
f: int := 0
for i: int in int$from_to(1,string$size(s)) do
if s[i] ~= t[i] then f := f-1 end
end
return(f)
end fitness
mutate = proc (mut: int, s: string) returns (string)
own charset: string := " ABCDEFGHIJKLMNOPQRSTUVWXYZ"
out: array[char] := array[char]$predict(1,string$size(s))
for c: char in string$chars(s) do
if random$next(10000) < mut then
c := charset[1+random$next(string$size(charset))]
end
array[char]$addh(out,c)
end
return(string$ac2s(out))
end mutate
weasel = iter (mut, c: int, tgt: string) yields (string)
own charset: string := " ABCDEFGHIJKLMNOPQRSTUVWXYZ"
start: array[char] := array[char]$[]
for i: int in int$from_to(1,string$size(tgt)) do
array[char]$addh(start,charset[1+random$next(string$size(charset))])
end
cur: string := string$ac2s(start)
while true do
yield(cur)
if cur = tgt then break end
best: string := cur
best_fitness: int := fitness(cur, tgt)
for i: int in int$from_to(2,c) do
next: string := mutate(mut, cur)
next_fitness: int := fitness(next, tgt)
if best_fitness <= next_fitness then
best, best_fitness := next, next_fitness
end
end
cur := best
end
end weasel
start_up = proc ()
d: date := now()
random$seed(d.second + 60*(d.minute + 60*d.hour))
po: stream := stream$primary_output()
for m: string in weasel(100, 1000, "METHINKS IT IS LIKE A WEASEL") do
stream$putl(po, m)
end
end start_up</lang>
- Output:
CQWBQKNNFKEOLFLXHGJYEWZYULBQ MQWBQKNNFKEOLFLXHGJYEWZYULBQ MQWBQKNNFKEOLFLXHGJYEWZEULBQ MEWBQKNNFKEOLFLXHGJYEWZEULBQ MEWBQKNNFKEOLFLXHKJYEWZEULBQ MEWBQKNNFKEOLFLXHKJYEWZEULBL MEWBQNNNFKEOLFLXHKJYEWZEULBL METBQNNNFKEOLFLXHKJYEWZEULBL METBQNNNFKEOLFLXHKJYE ZEULBL METBQNNSFKEOLFLXHKJYE ZEULBL METBQNNSFKEOLFLXHKEYE ZEULBL METBQNNSFKEOLFLXHKEYE ZEULEL METBQNNSFKEOLFLXIKEYE ZEULEL METEQNNSFKEOLFLLIKEYE ZEULEL METEQNNSFKEOLFLLIKE E ZEULEL METEQNKSFKEOLFLLIKE E ZEULEL METEQNKSFKEOLF LIKE E ZEULEL METEQNKSFKEOLF LIKE E ZEALEL METEQNKSFKEOIF LIKE E ZEALEL METEQNKSFKEOIF LIKE E ZEASEL METEQNKSFKTOIF LIKE E ZEASEL METEQNKS KTOIF LIKE E ZEASEL METEQNKS KTOIF LIKE E WEASEL METHQNKS KTOIF LIKE E WEASEL METHQNKS ITOIF LIKE E WEASEL METHQNKS ITOIF LIKE E WEASEL METHQNKS ITOIF LIKE A WEASEL METHQNKS IT IF LIKE A WEASEL METHQNKS IT IF LIKE A WEASEL METHQNKS IT IS LIKE A WEASEL METHQNKS IT IS LIKE A WEASEL METHQNKS IT IS LIKE A WEASEL METHINKS IT IS LIKE A WEASEL
COBOL
For testing purposes, you can comment out the first two sentences in the CONTROL-PARAGRAPH and the program will then use the same sequence of pseudo-random numbers on each run. <lang cobol>identification division. program-id. evolutionary-program. data division. working-storage section. 01 evolving-strings.
05 target pic a(28)
value 'METHINKS IT IS LIKE A WEASEL'.
05 parent pic a(28).
05 offspring-table.
10 offspring pic a(28)
occurs 50 times.
01 fitness-calculations.
05 fitness pic 99. 05 highest-fitness pic 99. 05 fittest pic 99.
01 parameters.
05 character-set pic a(27)
value 'ABCDEFGHIJKLMNOPQRSTUVWXYZ '.
05 size-of-generation pic 99
value 50.
05 mutation-rate pic 99
value 5.
01 counters-and-working-variables.
05 character-position pic 99.
05 randomization.
10 random-seed pic 9(8).
10 random-number pic 99.
10 random-letter pic 99.
05 generation pic 999.
05 child pic 99.
05 temporary-string pic a(28).
procedure division. control-paragraph.
accept random-seed from time. move function random(random-seed) to random-number. perform random-letter-paragraph, varying character-position from 1 by 1 until character-position is greater than 28. move temporary-string to parent. move zero to generation. perform output-paragraph. perform evolution-paragraph, varying generation from 1 by 1 until parent is equal to target. stop run.
evolution-paragraph.
perform mutation-paragraph varying child from 1 by 1 until child is greater than size-of-generation. move zero to highest-fitness. move 1 to fittest. perform check-fitness-paragraph varying child from 1 by 1 until child is greater than size-of-generation. move offspring(fittest) to parent. perform output-paragraph.
output-paragraph.
display generation ': ' parent.
random-letter-paragraph.
move function random to random-number. divide random-number by 3.80769 giving random-letter. add 1 to random-letter. move character-set(random-letter:1) to temporary-string(character-position:1).
mutation-paragraph.
move parent to temporary-string. perform character-mutation-paragraph, varying character-position from 1 by 1 until character-position is greater than 28. move temporary-string to offspring(child).
character-mutation-paragraph.
move function random to random-number. if random-number is less than mutation-rate then perform random-letter-paragraph.
check-fitness-paragraph.
move offspring(child) to temporary-string. perform fitness-paragraph.
fitness-paragraph.
move zero to fitness. perform character-fitness-paragraph, varying character-position from 1 by 1 until character-position is greater than 28. if fitness is greater than highest-fitness then perform fittest-paragraph.
character-fitness-paragraph.
if temporary-string(character-position:1) is equal to target(character-position:1) then add 1 to fitness.
fittest-paragraph.
move fitness to highest-fitness. move child to fittest.</lang>
- Output:
000: YZPLJKKFEZTWMSGAPVMUZBKBLLRS 001: YZPLJKKFEZTWMSGAPVMUZBKBLLRS 002: YZPLJKKFEZTWMS APVMUZBKBLLRS 003: JZPLJKKFEZTWMS AIVMUZBKBLLRS 004: JZPLJKKFEZTWMS AIVBUABKBLLRS 005: JZPLJKKFEZTWIS AIVBUABKBLLRS 006: JZPLJKKFEZTWIS AIVBUABKBLLRS 007: MVPLXKKFECTWIS AIVBUABKBLLRS 008: MVPLXKKSECTWIS AIVBUABKBLLRS 009: MVPLCKKSUCTWIS AIVBUABKBLLRS 010: MVPLCKKSUCTJIS LIVBVABKBLLRS 011: MVPLCKKSUCTJIS LIVBVABKBLSRS 012: MVPLCKKSUCTJIS LIVBQABKBLSRS 013: MVPLCKKSUCTJIS LIVBQABKBLSRS 014: MEPLCKKSUCTJIS LIVBQABKBLSRS 015: MEPVCKKSUCTJIS LIVBFABKBLSRS 016: MEPVCKKSUCTJIS LIVBFABKBLSRE 017: MEPVCKKSUCTJIS LIVBFABKBLSEE 018: MEPVCKKSUCTJIS LIVBFABWBLSEE 019: MEPVCKKSUCTJIS LIVBFABWBLSEE 020: MEPXCKKSUCTJIS LIVBFABWBLSEE 021: MEPXCKKSUCTJIS LIVBFABWBLSEE 022: MEPXCKKSUSTJIS LIVBFABWBLSEE 023: MEPXCKKSUSTJIS LIVBFABWBASEE 024: MEPXCKKSUSTJIS LIVEFABWBASEM 025: MEPXCKKSUSTJIS LIVEFABWEASEM 026: MEPXCKKSUSTJIS LIVEFABWEASEM 027: MEPXCKKSUITJIS LIVEFABWEASEM 028: MEPXCNKSUITJIS LIVEFABWEASEM 029: MEPXCNKSUITJIS LIVEFABWEASEM 030: MEPXCNKS ITJIS LIVEFABWEASEM 031: MEPXCNKS ITJIS LIVEFABWEASEM 032: MEPXCNKS ITJIS LIVEFABWEASEM 033: MEPXCNKS ITJIS LIVEFABWEASEM 034: MEPXCNKS ITNIS LIVEFABWEASEM 035: METICNKS ITNIS LIVEYABWEASEM 036: METICNKS ITNIS LIVEYABWEASEM 037: METICNKS ITMIS LIVEYABWEASEM 038: METIHNKS ITMIS LIVEYABWEASEM 039: METIHNKS ITMIS LIVEYABWEASEM 040: METIHNKS ITMIS LIKEYABWEASEM 041: METIHNKS IT IS LIKEYABWEASEM 042: METIHNKS IT IS LIKEYABWEASEM 043: METIHNKS IT IS LIKEPABWEASEM 044: METIHNKS IT IS LIKEPABWEASEM 045: METHHNKS IT IS LIKEPABWEASEM 046: METHHNKS IT IS LIKEPABWEASEM 047: METHHNKS IT IS LIKEPABWEASEM 048: METHHNKS IT IS LIKEPABWEASEM 049: METHHNKS IT IS LIKEPABWEASEM 050: METHHNKS IT IS LIKEPABWEASEM 051: METHHNKS IT IS LIKEPABWEASEM 052: METHHNKS IT IS LIKEPABWEASEL 053: METHHNKS IT IS LIKEPABWEASEL 054: METHHNKS IT IS LIKEPA WEASEL 055: METHHNKS IT IS LIKEPA WEASEL 056: METHHNKS IT IS LIKEPA WEASEL 057: METHINKS IT IS LIKEPA WEASEL 058: METHINKS IT IS LIKEPA WEASEL 059: METHINKS IT IS LIKECA WEASEL 060: METHINKS IT IS LIKECA WEASEL 061: METHINKS IT IS LIKEAA WEASEL 062: METHINKS IT IS LIKEAA WEASEL 063: METHINKS IT IS LIKEAA WEASEL 064: METHINKS IT IS LIKETA WEASEL 065: METHINKS IT IS LIKETA WEASEL 066: METHINKS IT IS LIKETA WEASEL 067: METHINKS IT IS LIKETA WEASEL 068: METHINKS IT IS LIKETA WEASEL 069: METHINKS IT IS LIKETA WEASEL 070: METHINKS IT IS LIKETA WEASEL 071: METHINKS IT IS LIKETA WEASEL 072: METHINKS IT IS LIKETA WEASEL 073: METHINKS IT IS LIKETA WEASEL 074: METHINKS IT IS LIKETA WEASEL 075: METHINKS IT IS LIKETA WEASEL 076: METHINKS IT IS LIKETA WEASEL 077: METHINKS IT IS LIKETA WEASEL 078: METHINKS IT IS LIKETA WEASEL 079: METHINKS IT IS LIKETA WEASEL 080: METHINKS IT IS LIKETA WEASEL 081: METHINKS IT IS LIKETA WEASEL 082: METHINKS IT IS LIKETA WEASEL 083: METHINKS IT IS LIKETA WEASEL 084: METHINKS IT IS LIKETA WEASEL 085: METHINKS IT IS LIKETA WEASEL 086: METHINKS IT IS LIKETA WEASEL 087: METHINKS IT IS LIKETA WEASEL 088: METHINKS IT IS LIKETA WEASEL 089: METHINKS IT IS LIKETA WEASEL 090: METHINKS IT IS LIKETA WEASEL 091: METHINKS IT IS LIKETA WEASEL 092: METHINKS IT IS LIKETA WEASEL 093: METHINKS IT IS LIKETA WEASEL 094: METHINKS IT IS LIKETA WEASEL 095: METHINKS IT IS LIKETA WEASEL 096: METHINKS IT IS LIKETA WEASEL 097: METHINKS IT IS LIKETA WEASEL 098: METHINKS IT IS LIKETA WEASEL 099: METHINKS IT IS LIKETA WEASEL 100: METHINKS IT IS LIKETA WEASEL 101: METHINKS IT IS LIKETA WEASEL 102: METHINKS IT IS LIKETA WEASEL 103: METHINKS IT IS LIKETA WEASEL 104: METHINKS IT IS LIKETA WEASEL 105: METHINKS IT IS LIKETA WEASEL 106: METHINKS IT IS LIKETA WEASEL 107: METHINKS IT IS LIKETA WEASEL 108: METHINKS IT IS LIKETA WEASEL 109: METHINKS IT IS LIKETA WEASEL 110: METHINKS IT IS LIKETA WEASEL 111: METHINKS IT IS LIKETA WEASEL 112: METHINKS IT IS LIKETA WEASEL 113: METHINKS IT IS LIKETA WEASEL 114: METHINKS IT IS LIKETA WEASEL 115: METHINKS IT IS LIKETA WEASEL 116: METHINKS IT IS LIKETA WEASEL 117: METHINKS IT IS LIKETA WEASEL 118: METHINKS IT IS LIKETA WEASEL 119: METHINKS IT IS LIKETA WEASEL 120: METHINKS IT IS LIKETA WEASEL 121: METHINKS IT IS LIKETA WEASEL 122: METHINKS IT IS LIKETA WEASEL 123: METHINKS IT IS LIKETA WEASEL 124: METHINKS IT IS LIKETA WEASEL 125: METHINKS IT IS LIKETA WEASEL 126: METHINKS IT IS LIKETA WEASEL 127: METHINKS IT IS LIKEDA WEASEL 128: METHINKS IT IS LIKEDA WEASEL 129: METHINKS IT IS LIKEDA WEASEL 130: METHINKS IT IS LIKEKA WEASEL 131: METHINKS IT IS LIKEKA WEASEL 132: METHINKS IT IS LIKEKA WEASEL 133: METHINKS IT IS LIKEKA WEASEL 134: METHINKS IT IS LIKEKA WEASEL 135: METHINKS IT IS LIKEKA WEASEL 136: METHINKS IT IS LIKEKA WEASEL 137: METHINKS IT IS LIKEKA WEASEL 138: METHINKS IT IS LIKEKA WEASEL 139: METHINKS IT IS LIKEKA WEASEL 140: METHINKS IT IS LIKEKA WEASEL 141: METHINKS IT IS LIKEKA WEASEL 142: METHINKS IT IS LIKEKA WEASEL 143: METHINKS IT IS LIKEKA WEASEL 144: METHINKS IT IS LIKEKA WEASEL 145: METHINKS IT IS LIKEKA WEASEL 146: METHINKS IT IS LIKEKA WEASEL 147: METHINKS IT IS LIKEKA WEASEL 148: METHINKS IT IS LIKEKA WEASEL 149: METHINKS IT IS LIKEKA WEASEL 150: METHINKS IT IS LIKEKA WEASEL 151: METHINKS IT IS LIKEKA WEASEL 152: METHINKS IT IS LIKEKA WEASEL 153: METHINKS IT IS LIKEKA WEASEL 154: METHINKS IT IS LIKEKA WEASEL 155: METHINKS IT IS LIKEKA WEASEL 156: METHINKS IT IS LIKEKA WEASEL 157: METHINKS IT IS LIKEKA WEASEL 158: METHINKS IT IS LIKEKA WEASEL 159: METHINKS IT IS LIKEKA WEASEL 160: METHINKS IT IS LIKEKA WEASEL 161: METHINKS IT IS LIKEKA WEASEL 162: METHINKS IT IS LIKEKA WEASEL 163: METHINKS IT IS LIKEKA WEASEL 164: METHINKS IT IS LIKEHA WEASEL 165: METHINKS IT IS LIKEHA WEASEL 166: METHINKS IT IS LIKEHA WEASEL 167: METHINKS IT IS LIKEHA WEASEL 168: METHINKS IT IS LIKEHA WEASEL 169: METHINKS IT IS LIKEHA WEASEL 170: METHINKS IT IS LIKEYA WEASEL 171: METHINKS IT IS LIKEYA WEASEL 172: METHINKS IT IS LIKEYA WEASEL 173: METHINKS IT IS LIKEYA WEASEL 174: METHINKS IT IS LIKEYA WEASEL 175: METHINKS IT IS LIKEYA WEASEL 176: METHINKS IT IS LIKEYA WEASEL 177: METHINKS IT IS LIKEYA WEASEL 178: METHINKS IT IS LIKEYA WEASEL 179: METHINKS IT IS LIKEYA WEASEL 180: METHINKS IT IS LIKEYA WEASEL 181: METHINKS IT IS LIKEYA WEASEL 182: METHINKS IT IS LIKEYA WEASEL 183: METHINKS IT IS LIKEYA WEASEL 184: METHINKS IT IS LIKEYA WEASEL 185: METHINKS IT IS LIKEYA WEASEL 186: METHINKS IT IS LIKEYA WEASEL 187: METHINKS IT IS LIKEYA WEASEL 188: METHINKS IT IS LIKEYA WEASEL 189: METHINKS IT IS LIKEZA WEASEL 190: METHINKS IT IS LIKEZA WEASEL 191: METHINKS IT IS LIKEZA WEASEL 192: METHINKS IT IS LIKEZA WEASEL 193: METHINKS IT IS LIKEZA WEASEL 194: METHINKS IT IS LIKE A WEASEL
ColdFusion
<lang cfm> <Cfset theString = 'METHINKS IT IS LIKE A WEASEL'> <cfparam name="parent" default=""> <Cfset theAlphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ "> <Cfset fitness = 0> <Cfset children = 3> <Cfset counter = 0>
<Cfloop from="1" to="#children#" index="child">
<Cfparam name="child#child#" default=""> <Cfparam name="fitness#child#" default=0>
</Cfloop>
<Cfloop condition="fitness lt 1">
<Cfset oldparent = parent> <Cfset counter = counter + 1>
<cfloop from="1" to="#children#" index="child">
<Cfset thischild = >
<Cfloop from="1" to="#len(theString)#" index="i">
<cfset Mutate = Mid(theAlphabet, RandRange(1, 28), 1)>
<cfif fitness eq 0>
<Cfset thischild = thischild & mutate>
<Cfelse>
<Cfif Mid(theString, i, 1) eq Mid(variables["child" & child], i, 1)>
<Cfset thischild = thischild & Mid(variables["child" & child], i, 1)>
<Cfelse>
<cfset MutateChance = 1/fitness>
<Cfset MutateChanceRand = rand()>
<Cfif MutateChanceRand lte MutateChance>
<Cfset thischild = thischild & mutate>
<Cfelse>
<Cfset thischild = thischild & Mid(variables["child" & child], i, 1)>
</Cfif>
</Cfif>
</cfif>
</Cfloop>
<Cfset variables["child" & child] = thischild>
</cfloop>
<cfloop from="1" to="#children#" index="child">
<Cfset thisChildFitness = 0>
<Cfloop from="1" to="#len(theString)#" index="i">
<Cfif Mid(variables["child" & child], i, 1) eq Mid(theString, i, 1)>
<Cfset thisChildFitness = thisChildFitness + 1>
</Cfif>
</Cfloop>
<Cfset variables["fitness" & child] = (thisChildFitness)/len(theString)>
<Cfif variables["fitness" & child] gt fitness>
<Cfset fitness = variables["fitness" & child]>
<Cfset parent = variables["child" & child]>
</Cfif>
</cfloop> <Cfif parent neq oldparent> <Cfoutput>###counter# #numberformat(fitness*100, 99)#% fit: #parent#
</Cfoutput><cfflush> </Cfif>
</Cfloop> </lang>
#1 7% fit: VOPJOBSYPTTUNYYSAFHTPJUIAIL #2 18% fit: FQUFHEKPLXTQISYZZRIEVQWBHRC #3 21% fit: MGTUKIRICATKDDMSIUNDERUAASKT #33 29% fit: M THILKORWP XSRVOLV GVIRVJHE #34 36% fit: MEBHRNTSYPH IHTCHMH LGWBAFZ #37 39% fit: MSTHIWKLIHU KSSLECR Z WGUMZE #61 43% fit: METHINKA RT ZRQCEFVEAMWKZEBA #62 50% fit: METHINKA GT RLQAOHVSAXWNAS A #67 54% fit: MESHINKT IGBWSRLIEEAF WERYWH #72 57% fit: METHINKE VT YBUJNRXRA W XSEL #129 64% fit: METHINKS ITCIEHLPNB A YYAAPL #156 68% fit: METHINKS IT IHIWJKY I W GSAL #177 71% fit: METHINKS IT IS RIPRPA BEAVYN #180 75% fit: METHINKS IT IS OI BAA TEABBL #185 79% fit: METHINKS IT IS LIQEWA EEARLX #197 82% fit: METHINKS IT IS LIKP OKWEASMU #222 86% fit: METHINKS IT IS LIKESG WEALEH #245 89% fit: METHINKS IT IS LIKEOA GEAQEL #304 93% fit: METHINKS IT IS LIKE A WESSYL #349 96% fit: METHINKS IT IS LIKE A WEASOL #360 100% fit: METHINKS IT IS LIKE A WEASEL
Commodore BASIC
Finding the target string takes roughly two hours on a Commodore 64.
<lang gwbasic>10 N=100:P=0.05:TI$="000000" 20 Z$="METHINKS IT IS LIKE A WEASEL" 30 L=LEN(Z$) 40 DIMX(N,L) 50 FORI=1TOL 60 IFMID$(Z$,I,1)=" "THENX(0,I)=0:GOTO80 70 X(0,I)=ASC(MID$(Z$,I))-64 80 NEXT 90 FORK=1TON:FORI=1TOL:X(K,I)=INT(RND(0)*27):NEXT:NEXT 100 S=-100:B=0 110 K=B:GOSUB300 120 FORK=1TON:IFK=BTHEN150 130 FORI=1TOL:IFRND(.)<PTHENX(K,I)=INT(RND(0)*27) 140 NEXT 150 NEXT 160 S=-100:B=0 170 FORK=1TON 180 F=0:FORI=1TOL:IFX(K,I)<>X(0,I)THENF=F-1:IFF<STHENI=L 190 NEXT:IFF>STHENS=F:B=K 200 NEXT 210 PRINT"BEST:"B;"SCORE:"S 220 IFS=0THEN270 230 FORK=1TON:IFK=BTHEN250 240 FORI=1TOL:X(K,I)=X(B,I):NEXT 250 NEXT 260 GOTO110 270 PRINT"WE HAVE A WEASEL!":K=B:GOSUB300 280 PRINT"TIME:"TI$:END 300 FORI=1TOL:IFX(K,I)THENPRINTCHR$(64+X(K,I));:GOTO320 310 PRINT" "; 320 NEXT:PRINT"<":RETURN</lang>
Output during calculation (excerpt):
BEST: 23 SCORE:-21 PJKJELKRRIWZITLOCKXTNYLNASEY< BEST: 3 SCORE:-20 PJKJENKRRIWZITLOCKXTNJLNASEY< BEST: 14 SCORE:-19 PJKJENKSRIWZITLOCKXTNJLNASEY< BEST: 79 SCORE:-18 PJKJENKSRIW ITLOCKXTNJLNASEY< BEST: 50 SCORE:-17 PJKUENKSRIW ITLOCKXTN LNASEY< BEST: 12 SCORE:-16 PJKUINKSRIW ITLOCKHTN LNASEY< BEST: 8 SCORE:-15 PJKUINKSSIK ITLOCKHTA LNASEY< BEST: 21 SCORE:-14 PJKHINKSSIK ITLOCKHTA LNASEY< BEST: 30 SCORE:-13 PJTHINKSSIK ITTOCKHTA LOASEY< BEST: 48 SCORE:-12 PJTHINKS IK ITTOCKHTA LOASEY< BEST: 1 SCORE:-12 PJTHINKS IK ITTOCKHTA LOASEY< BEST: 29 SCORE:-11 PJTHINKS IK IT OCKHTA LOASEY<
Common Lisp
<lang lisp>(defun fitness (string target)
"Closeness of string to target; lower number is better"
(loop for c1 across string
for c2 across target
count (char/= c1 c2)))
(defun mutate (string chars p)
"Mutate each character of string with probablity p using characters from chars"
(dotimes (n (length string))
(when (< (random 1.0) p)
(setf (aref string n) (aref chars (random (length chars))))))
string)
(defun random-string (chars length)
"Generate a new random string consisting of letters from char and specified length"
(do ((n 0 (1+ n))
(str (make-string length)))
((= n length) str)
(setf (aref str n) (aref chars (random (length chars))))))
(defun evolve-string (target string chars c p)
"Generate new mutant strings, and choose the most fit string"
(let ((mutated-strs (list string)))
(dotimes (n c)
(push (mutate (copy-seq string) chars p) mutated-strs))
(reduce #'(lambda (s0 s1)
(if (< (fitness s0 target)
(fitness s1 target))
s0
s1))
mutated-strs)))
(defun evolve-gens (target c p)
(let ((chars " ABCDEFGHIJKLMNOPQRSTUVWXYZ"))
(do ((parent (random-string chars (length target))
(evolve-string target parent chars c p))
(n 0 (1+ n)))
((string= target parent) (format t "Generation ~A: ~S~%" n parent))
(format t "Generation ~A: ~S~%" n parent))))</lang>
Sample output:
CL-USER> (evolve-gens "METHINKS IT IS LIKE A WEASEL" 100 0.05) Generation 0: "IFNGR ACQNOAWQZYHNIUPLRHTPCP" Generation 1: "IUNGRHAC NOAWQZYHNIUPLRHTPCP" Generation 2: "IUNGRHAC YO WQZYHNIUPLRHTPCP" Generation 3: "IUNGRHKC YO WQZYHNIUPLJHTPRP" Generation 4: "IUNGRHKC IO WQZYHVIUPLVHTPRP" Generation 5: "IUNGRNKC IO WQZYHVIUPLVHNPRP" Generation 6: "IUNGRNKC IO WQZYHVIUPLVHNPRP" Generation 7: "IENGRNKC IO WQZYHVIUPLVHNPRP" Generation 8: "IENGRNKC IO WQZYHVEURLVHNPRP" Generation 9: "IENMRNKC IO WQZYHVE RLVHNPRP" Generation 10: "IENMRNKC IO WQZYHVE RLVHNPRP" Generation 11: "IENMRNKC IO WQZYHVE RLVHNPRP" Generation 12: "IEZMRNKC IO WQZYAVE RLVHNSRP" Generation 13: "IEZMRNKC IO WQZYIVE RLVHNSRP" Generation 14: "IEZMRNKC IO WQZYIKE RLVHNSRP" Generation 15: "IEZMRNKC IO WQZYIKE RLVHNSRL" Generation 16: "IEZ INKC IZ WQZYIKE RLVHNSRL" Generation 17: "IET INKC IZ WQZYIKE RLVHNSRL" Generation 18: "IET INKC IZ WQZYIKE RLVHNSEL" Generation 19: "IET INKC IZ WQZ IKE RLVHASEL" Generation 20: "GET INKC IZ WSZ IKE RLVHASEL" Generation 21: "GET INKC IZ WSZ IKE RLVHASEL" Generation 22: "GET INKC IZ WSZ IKE RLVHASEL" Generation 23: "GET INKC IZ ISZ IKE RLVHASEL" Generation 24: "GET INKC IZ ISZ IKE RLWHASEL" Generation 25: "MET INKC IZ ISZ IKE OLWHASEL" Generation 26: "MET INKC IZ ISZ IKE OLWHASEL" Generation 27: "MET INKC IZ ISZ IKE ALWHASEL" Generation 28: "MET INKC IZ ISZ IKE A WHASEL" Generation 29: "METHINKC IZ ISZ IKE A WHASEL" Generation 30: "METHINKC IZ ISZ IKE A WHASEL" Generation 31: "METHINKC IZ ISZ IKE A WHASEL" Generation 32: "METHINKC IZ ISZ IKE A WEASEL" Generation 33: "METHINKC IZ ISZ IKE A WEASEL" Generation 34: "METHINKC IZ ISZ IKE A WEASEL" Generation 35: "METHINKC IT ISZLIKD A WEASEL" Generation 36: "METHINKC IT ISZLIKD A WEASEL" Generation 37: "METHINKC IT ISZLIKD A WEASEL" Generation 38: "METHINKC IT ISZLIKD A WEASEL" Generation 39: "METHINKC IT ISZLIKD A WEASEL" Generation 40: "METHINKC IT ISZLIKE A WEASEL" Generation 41: "METHINKC IT IS LIKE A WEASEL" Generation 42: "METHINKC IT IS LIKE A WEASEL" Generation 43: "METHINKS IT IS LIKE A WEASEL"
Mutates one character at a time, with only on offspring each generation (which competes against the parent): <lang lisp>(defun unfit (s1 s2)
(loop for a across s1
for b across s2 count(char/= a b)))
(defun mutate (str alp n) ; n: number of chars to mutate
(let ((out (copy-seq str))) (dotimes (i n) (setf (char out (random (length str)))
(char alp (random (length alp)))))
out))
(defun evolve (changes alpha target)
(loop for gen from 1
with f2 with s2 with str = (mutate target alpha 100) with fit = (unfit target str) while (plusp fit) do (setf s2 (mutate str alpha changes) f2 (unfit target s2)) (when (> fit f2) (setf str s2 fit f2) (format t "~5d: ~a (~d)~%" gen str fit))))
(evolve 1 " ABCDEFGHIJKLMNOPQRSTUVWXYZ" "METHINKS IT IS LIKE A WEASEL")</lang>outupt<lang> 44: DYZTOREXDML ZCEUCSHRVHBEPGJE (26)
57: DYZTOREXDIL ZCEUCSHRVHBEPGJE (25) 83: DYZTOREX IL ZCEUCSHRVHBEPGJE (24) 95: MYZTOREX IL ZCEUCSHRVHBEPGJE (23) 186: MYZTOREX IL ZCEUISHRVHBEPGJE (22) 208: MYZTOREX IL ZCEUISH VHBEPGJE (21) 228: MYZTOREX IL ZCEUISH VHBEPGEE (20) 329: MYZTOREX IL ZCEUIKH VHBEPGEE (19) 330: MYTTOREX IL ZCEUIKH VHBEPGEE (18) 354: MYTHOREX IL ZCEUIKH VHBEPGEE (17) 365: MYTHOREX IL ICEUIKH VHBEPGEE (16) 380: MYTHOREX IL ISEUIKH VHBEPGEE (15) 393: METHOREX IL ISEUIKH VHBEPGEE (14) 407: METHORKX IL ISEUIKH VHBEPGEE (13) 443: METHORKX IL ISEUIKH VHBEPSEE (12) 455: METHORKX IL ISEUIKE VHBEPSEE (11) 477: METHIRKX IL ISEUIKE VHBEPSEE (10) 526: METHIRKS IL ISEUIKE VHBEPSEE (9) 673: METHIRKS IL ISEUIKE VHBEPSEL (8) 800: METHINKS IL ISEUIKE VHBEPSEL (7) 875: METHINKS IL ISEUIKE AHBEPSEL (6) 941: METHINKS IL ISEUIKE AHBEASEL (5) 1175: METHINKS IT ISEUIKE AHBEASEL (4) 1214: METHINKS IT ISELIKE AHBEASEL (3) 1220: METHINKS IT IS LIKE AHBEASEL (2) 1358: METHINKS IT IS LIKE AHWEASEL (1) 2610: METHINKS IT IS LIKE A WEASEL (0)</lang>
D
<lang d>import std.stdio, std.random, std.algorithm, std.range, std.ascii;
enum target = "METHINKS IT IS LIKE A WEASEL"d; enum C = 100; // Number of children in each generation. enum P = 0.05; // Mutation probability. enum fitness = (dchar[] s) => target.zip(s).count!q{ a[0] != a[1] }; dchar rnd() { return (uppercase ~ " ")[uniform(0, $)]; } enum mut = (dchar[] s) => s.map!(a => uniform01 < P ? rnd : a).array;
void main() {
auto parent = generate!rnd.take(target.length).array;
for (auto gen = 1; parent != target; gen++) {
// parent = parent.repeat(C).map!mut.array.max!fitness;
parent = parent.repeat(C).map!mut.array
.minPos!((a, b) => a.fitness < b.fitness)[0];
writefln("Gen %2d, dist=%2d: %s", gen, parent.fitness, parent);
}
}</lang>
- Output:
Generation 0, dist=25: PTJNKPFVJFTDRSDVNUB ESJGU MF Generation 1, dist=18: PEKNKNKSBFTDISDVIUB ESJEP MF Generation 2, dist=12: NETVKNKS FTDISDLIUE EIJEPSEF Generation 3, dist= 8: NETVONKS ITDISDLIUE AIWEASEF Generation 4, dist= 8: NETVONKS ITDISDLIUE AIWEASEF Generation 5, dist= 6: NETHONKS ITDIS LINE AIWEASEW Generation 6, dist= 5: NETHINKS ITSIS LINE AIWEASEW Generation 7, dist= 5: NETHINKS ITSIS LINE AIWEASEW Generation 8, dist= 4: NETHINKS ITSIS LINE A WEASEW Generation 9, dist= 3: METHINKS ITSIS LINE A WEASEW Generation 10, dist= 3: METHINKS ITSIS LINE A WEASEW Generation 11, dist= 3: METHINKS ITSIS LINE A WEASEW Generation 12, dist= 2: METHINKS IT IS LINE A WEASEW Generation 13, dist= 2: METHINKS IT IS LINE A WEASEW Generation 14, dist= 1: METHINKS IT IS LIKE A WEASEW Generation 15, dist= 1: METHINKS IT IS LIKE A WEASEW Generation 16, dist= 1: METHINKS IT IS LIKE A WEASEW Generation 17, dist= 1: METHINKS IT IS LIKE A WEASEW Generation 18, dist= 1: METHINKS IT IS LIKE A WEASEW Generation 19, dist= 1: METHINKS IT IS LIKE A WEASEW Generation 20, dist= 1: METHINKS IT IS LIKE A WEASEW Generation 21, dist= 1: METHINKS IT IS LIKE A WEASEW Generation 22, dist= 1: METHINKS IT IS LIKE A WEASEW Generation 23, dist= 1: METHINKS IT IS LIKE A WEASEW Generation 24, dist= 0: METHINKS IT IS LIKE A WEASEL
Delphi
See Pascal.
E
<lang e>pragma.syntax("0.9") pragma.enable("accumulator")
def target := "METHINKS IT IS LIKE A WEASEL" def alphabet := "ABCDEFGHIJKLMNOPQRSTUVWXYZ " def C := 100 def RATE := 0.05
def randomCharString() {
return E.toString(alphabet[entropy.nextInt(alphabet.size())])
}
def fitness(string) {
return accum 0 for i => ch in string {
_ + (ch == target[i]).pick(1, 0)
}
}
def mutate(string, rate) {
return accum "" for i => ch in string {
_ + (entropy.nextDouble() < rate).pick(randomCharString(), E.toString(ch))
}
}
def weasel() {
var parent := accum "" for _ in 1..(target.size()) { _ + randomCharString() }
var generation := 0
while (parent != target) {
println(`$generation $parent`)
def copies := accum [] for _ in 1..C { _.with(mutate(parent, RATE)) }
var best := parent
for c in copies {
if (fitness(c) > fitness(best)) {
best := c
}
}
parent := best
generation += 1
}
println(`$generation $parent`)
}
weasel()</lang>
EchoLisp
<lang scheme> (require 'sequences) (define ALPHABET (list->vector ["A" .. "Z"] )) (vector-push ALPHABET " ")
(define (fitness source target) ;; score >=0, best is 0 (for/sum [(s source)(t target)] (if (= s t) 0 1)))
(define (mutate source rate) (for/string [(s source)] (if (< (random) rate) [ALPHABET (random 27)] s)))
(define (select parent target rate copies (copy) (score)) (define best (fitness parent target)) (define selected parent) (for [(i copies)] (set! copy (mutate parent rate)) (set! score (fitness copy target)) (when (< score best) (set! selected copy) (set! best score))) selected )
(define MUTATION_RATE 0.05) ;; 5% chances to change (define COPIES 100) (define TARGET "METHINKS IT IS LIKE A WEASEL")
(define (task (rate MUTATION_RATE) (copies COPIES) (target TARGET) (score)) (define parent ;; random source (for/string
[(i (string-length target))] [ALPHABET (random 27)]))
(for [(i (in-naturals))] (set! score (fitness parent target)) (writeln i parent 'score score) #:break (zero? score) (set! parent (select parent target rate copies)) )) </lang>
- Output:
(task) 0 "TNCEKMNVYOW NSMSZ BZDODMMAXE" score 26 1 "TNCEKBNVYOW NSMSZ AZDODMMAEE" score 25 2 "TNCEKINVYOW NSMSZKEZDODMMAEE" score 23 3 "TNCEKIKVYOW NSMSZKEZDODMMAEE" score 22 4 "TNCEKIKVYOW NSMSZKEZDOWMMAEE" score 21 5 "TNCEKIKVYOW NSMSZKEZDOWMMAEE" score 21 6 "MNCEKIKVYOW NSMSZKEZSOWMMAEE" score 20 7 "MNCEKIKAYOE NSMLZKEZSOWMMAEE" score 19 8 "MNCEKIKAYOE NSMLZKEZS WMMAEE" score 18 9 "MNCEKIKAYOE ISMLZKEZS WMMAEE" score 17 10 "MECEKIKAYBE ISMLZKEZS WMMAEE" score 16 11 "MECEKLKAYBE ISMLZKE S WMMAEE" score 15 12 "METEKZKAYBE ISMLZKE S WMMAEE" score 14 13 "METEKZKAYBE ISMLZKE S WMMSEE" score 13 14 "METEIZKAYBE ISMLZKE S WMMSEH" score 12 15 "METEIZKAYBE ISMLZKE S WMMSEH" score 12 16 "METHIZKAYBE ISMLZKE S WMMSEH" score 11 17 "METHIZKAYBE ISMLZKE S WMASEH" score 10 18 "METHIZKAYBE ISMLZKE S WMASEH" score 10 [...] 67 "METHINKS RT ISMLIKE A WEASEL" score 2 68 "METHINKS RT ISMLIKE A WEASEL" score 2 69 "METHINKS RT ISMLIKE A WEASEL" score 2 70 "METHINKS RT ISMLIKE A WEASEL" score 2 71 "METHINKS RT ISMLIKE A WEASEL" score 2 72 "METHINKS RT IS LIKE A WEASEL" score 1 73 "METHINKS RT IS LIKE A WEASEL" score 1 74 "METHINKS RT IS LIKE A WEASEL" score 1 75 "METHINKS IT IS LIKE A WEASEL" score 0
Elena
ELENA 5.0 : <lang elena>import system'routines; import extensions; import extensions'text;
const string Target = "METHINKS IT IS LIKE A WEASEL"; const string AllowedCharacters = " ABCDEFGHIJKLMNOPQRSTUVWXYZ";
const int C = 100; const real P = 0.05r;
rnd = randomGenerator;
randomChar
= AllowedCharacters[rnd.nextInt(AllowedCharacters.Length)];
extension evoHelper {
randomString()
= 0.repeatTill(self).selectBy:(x => randomChar).summarize(new StringWriter());
fitnessOf(s)
= self.zipBy(s, (a,b => a==b ? 1 : 0)).summarize(new Integer()).toInt();
mutate(p)
= self.selectBy:(ch => rnd.nextReal() <= p ? randomChar : ch).summarize(new StringWriter());
}
class EvoAlgorithm : Enumerator {
object theTarget; object theCurrent; object theVariantCount;
constructor new(s,count)
{
theTarget := s;
theVariantCount := count.toInt();
}
get() = theCurrent;
bool next()
{
if (nil == theCurrent)
{ theCurrent := theTarget.Length.randomString(); ^ true };
if (theTarget == theCurrent)
{ ^ false };
auto variants := Array.allocate(theVariantCount).populate:(x => theCurrent.mutate:P );
theCurrent := variants.sort:(a,b => a.fitnessOf:Target > b.fitnessOf:Target ).at:0;
^ true
}
reset()
{
theCurrent := nil
}
enumerable() => theTarget;
}
public program() {
var attempt := new Integer();
EvoAlgorithm.new(Target,C).forEach:(current)
{
console
.printPaddingLeft(10,"#",attempt.append(1))
.printLine(" ",current," fitness: ",current.fitnessOf(Target))
};
console.readChar()
}</lang>
- Output:
#1 WYHOOITVJKCPTOOTEVZJUNLCFDCV fitness: 0
#2 WYHOOITV KCPTOOTEVZJUNLCFDCV fitness: 1
#3 WYHOOITS KCPTOCTEVZ UNLCFDCV fitness: 3
#4 WYHO ITS KCPTO TEVZ UELCFDCV fitness: 4
#5 WYGO ITS DC ZO TEVZ UELCFDCV fitness: 5
#6 WYGO ITS DC ZO TEVZ UELCADCV fitness: 6
#7 WYGO ITS DT ZO TEVZ UELCADCV fitness: 7
#8 WYGOIITS DT ZO TEVZ LELCADRV fitness: 8
#9 WYGOIITS DT ZO TEVZ LELCADRL fitness: 9
#10 WYTOIITS HT ZZ TEVZ LEQCADRL fitness: 10
#11 WYTOIITS HT ZZ IEKZ LEQCADRL fitness: 11
#12 WYTOIITS HT ZZ IEKZ LEQCADEL fitness: 12
#13 WYTOIITS HT ZZ IEKZ LEQCASEL fitness: 13
#14 WYTOIIKS HT BZ IEKZ LEQCASEL fitness: 14
...
#34 METHINKS GT BS LGKE AEWGASEL fitness: 23
#35 METHINKS GT BS LIKE AEWGASEL fitness: 24
#36 METHINKS GT BS LIKE AEWGASEL fitness: 24
#37 METHINKS GT BS LIKE AEWGASEL fitness: 24
#38 METHINKS GT BS LIKE AEWGASEL fitness: 24
#39 METHINKS GT IS LIKE AEWYASEL fitness: 25
#40 METHINKS GT IS LIKE AEWYASEL fitness: 25
#41 METHINKS GT IS LIKE AEWEASEL fitness: 26
#42 METHINKS GT IS LIKE AEWEASEL fitness: 26
#43 METHINKS GT IS LIKE AEWEASEL fitness: 26
#44 METHINKS GT IS LIKE AEWEASEL fitness: 26
#45 METHINKS GT IS LIKE AEWEASEL fitness: 26
#46 METHINKS GT IS LIKE AEWEASEL fitness: 26
#47 METHINKS GT IS LIKE AEWEASEL fitness: 26
...
#57 METHINKS GT IS LIKE A WEASEL fitness: 27
#58 METHINKS GT IS LIKE A WEASEL fitness: 27
#59 METHINKS GT IS LIKE A WEASEL fitness: 27
#60 METHINKS GT IS LIKE A WEASEL fitness: 27
#61 METHINKS GT IS LIKE A WEASEL fitness: 27
#62 METHINKS GT IS LIKE A WEASEL fitness: 27
#63 METHINKS GT IS LIKE A WEASEL fitness: 27
#64 METHINKS LT IS LIKE A WEASEL fitness: 27
#65 METHINKS LT IS LIKE A WEASEL fitness: 27
#66 METHINKS LT IS LIKE A WEASEL fitness: 27
#67 METHINKS LT IS LIKE A WEASEL fitness: 27
#68 METHINKS LT IS LIKE A WEASEL fitness: 27
#69 METHINKS LT IS LIKE A WEASEL fitness: 27
#70 METHINKS LT IS LIKE A WEASEL fitness: 27
#71 METHINKS IT IS LIKE A WEASEL fitness: 28
Elixir
Print current gen and most fit offspring if more fit than parent.
Print the target and the total number of generations (iterations) it took to reach it.
<lang Elixir>defmodule Log do
def show(offspring,i) do
IO.puts "Generation: #{i}, Offspring: #{offspring}"
end
def found({target,i}) do
IO.puts "#{target} found in #{i} iterations"
end
end
defmodule Evolution do
# char list from A to Z; 32 is the ord value for space.
@chars [32 | Enum.to_list(?A..?Z)]
def select(target) do
(1..String.length(target)) # Creates parent for generation 0.
|> Enum.map(fn _-> Enum.random(@chars) end)
|> mutate(to_charlist(target),0)
|> Log.found
end
# w is used to denote fitness in population genetics.
defp mutate(parent,target,i) when target == parent, do: {parent,i}
defp mutate(parent,target,i) do
w = fitness(parent,target)
prev = reproduce(target,parent,mu_rate(w))
# Check if the most fit member of the new gen has a greater fitness than the parent.
if w < fitness(prev,target) do
Log.show(prev,i)
mutate(prev,target,i+1)
else
mutate(parent,target,i+1)
end
end
# Generate 100 offspring and select the one with the greatest fitness.
defp reproduce(target,parent,rate) do
[parent | (for _ <- 1..100, do: mutation(parent,rate))]
|> Enum.max_by(fn n -> fitness(n,target) end)
end
# Calculate fitness by checking difference between parent and offspring chars.
defp fitness(t,r) do
Enum.zip(t,r)
|> Enum.reduce(0, fn {tn,rn},sum -> abs(tn - rn) + sum end)
|> calc
end
# Generate offspring based on parent.
defp mutation(p,r) do
# Copy the parent chars, then check each val against the random mutation rate
Enum.map(p, fn n -> if :rand.uniform <= r, do: Enum.random(@chars), else: n end)
end
defp calc(sum), do: 100 * :math.exp(sum/-10)
defp mu_rate(n), do: 1 - :math.exp(-(100-n)/400)
end
Evolution.select("METHINKS IT IS LIKE A WEASEL")</lang>
- Output:
Generation: 0, Offspring: AFOSPRRLTLF CQKYFIGUMEUVBLRN Generation: 1, Offspring: HFOMJRRESLL FQKYQRGUM UVBLRN Generation: 2, Offspring: HFOMCRLIDLL FDKYQRGNM UVBLIN Generation: 3, Offspring: HFOMCOLIDQL FDKYQRG M UVBLIP Generation: 4, Offspring: HFOMCOLVLRL FD YYRG M UEBLIP Generation: 5, Offspring: HFOMCOLVLRL FS YYNH M UEBXJP Generation: 6, Offspring: KFOMCOLVLRL FS YYNH C UEBXJP Generation: 7, Offspring: EFOFCOCVLFT FV YCNH C UEBMJP Generation: 8, Offspring: EFWFCOCV FTBFV YCSH C UEBMJP Generation: 9, Offspring: EFWFJOCZ FTBRV DCMH C UEBMJP Generation: 11, Offspring: PFSFJOCL FVBRV DCMH C UEBJJP Generation: 12, Offspring: PFSDJYCL LV RK DKMH C UEBJJR Generation: 13, Offspring: IFSDJYCP LV MK DKMH C UEBSJR Generation: 14, Offspring: IFSDJTIP LV MK DKMH C UEBSGR Generation: 15, Offspring: IFSDJTIO JV MK SKMH C UEBSGR Generation: 16, Offspring: IFSKIJIO JV MK DKMH C UEBSGG Generation: 19, Offspring: IFSJIJIP JV MK DKIH C UEBSGH Generation: 20, Offspring: IFSJIJIP JV MO DMIH C UEBSGH Generation: 21, Offspring: IFWJDJIP JV IO EHJH C UEBSGH Generation: 23, Offspring: IFWJDJIP JV IO SHJH A XEBSGH Generation: 25, Offspring: IFWJDJIP JV IO SHJC A XEBSGH Generation: 26, Offspring: IFWJKJIP JV IO LHJC A XEBOGH Generation: 34, Offspring: IFTJKJIT JV IO LHJC A XEBOGH Generation: 39, Offspring: IFTJKOIT JV IO LHJC A XEBOGH Generation: 53, Offspring: IETJKOIT JV IO LHJC A XEBOGH Generation: 60, Offspring: IETJKOIT JV IO LHJC A XEBOEG Generation: 64, Offspring: IETJKOIT JV IO LHJF A XEBOEG Generation: 68, Offspring: LETGKOIT JV IO LHJF A XEBOEG Generation: 70, Offspring: LETGKOIT JV IS LHJF A XEBOBG Generation: 76, Offspring: LETEKOIT JV IS LHJF A XEBOBN Generation: 83, Offspring: LETHKOIT JV IS LHJF A XEBOFN Generation: 90, Offspring: LBTHKOIT JV IS LHJF A XEBSFN Generation: 92, Offspring: LBTHKOIT JV IS LHJF A XEBSFL Generation: 93, Offspring: LBTHKOJT JV IS LHJF A XEBSFL Generation: 123, Offspring: LETHKOJT JV IS LHJF A XEBSFL Generation: 125, Offspring: LETHHOJT JV IS LHJF A XEBSFL Generation: 135, Offspring: LETHHOJT JV IS LIJF A XEBSFL Generation: 143, Offspring: LETHHOJT IV IS LIJF A XEBSFL Generation: 161, Offspring: LETHHNJT IV IS LIJF A XEBSFL Generation: 165, Offspring: METHHNJT IV IS LIJF A XEBSFL Generation: 169, Offspring: METHHNKT IV IS LIJF A XEBSFL Generation: 171, Offspring: METHHNKT IV IS LIJE A XEBSFL Generation: 175, Offspring: METHHNKT IS IS LIJE A XEBSFL Generation: 213, Offspring: METHHNKT IS IS LIKE A XEBSFL Generation: 218, Offspring: METHINKT IS IS LIKE A XEBSFL Generation: 234, Offspring: METHINKT IS IS LIKE A XEBSEL Generation: 237, Offspring: METHINKT IS IS LIKE A XEASEL Generation: 241, Offspring: METHINKT IS IS LIKE A WEASEL Generation: 243, Offspring: METHINKT IT IS LIKE A WEASEL Generation: 247, Offspring: METHINKS IT IS LIKE A WEASEL METHINKS IT IS LIKE A WEASEL found in 248 iterations
Erlang
<lang erlang>-module(evolution). -export([run/0]).
-define(MUTATE, 0.05). -define(POPULATION, 100). -define(TARGET, "METHINKS IT IS LIKE A WEASEL"). -define(MAX_GENERATIONS, 1000).
run() -> evolve_gens().
evolve_gens() ->
Initial = random_string(length(?TARGET)), evolve_gens(Initial,0,fitness(Initial)).
evolve_gens(Parent,Generation,0) ->
io:format("Generation[~w]: Achieved the target: ~s~n",[Generation,Parent]);
evolve_gens(Parent,Generation,_Fitness) when Generation == ?MAX_GENERATIONS ->
io:format("Reached Max Generations~nFinal string is ~s~n",[Parent]);
evolve_gens(Parent,Generation,Fitness) ->
io:format("Generation[~w]: ~s, Fitness: ~w~n",
[Generation,Parent,Fitness]),
Child = evolve_string(Parent),
evolve_gens(Child,Generation+1,fitness(Child)).
fitness(String) -> fitness(String, ?TARGET). fitness([],[]) -> 0; fitness([H|Rest],[H|Target]) -> fitness(Rest,Target); fitness([_H|Rest],[_T|Target]) -> 1+fitness(Rest,Target).
mutate(String) -> mutate(String,[]). mutate([],Acc) -> lists:reverse(Acc); mutate([H|T],Acc) ->
case random:uniform() < ?MUTATE of
true ->
mutate(T,[random_character()|Acc]);
false ->
mutate(T,[H|Acc])
end.
evolve_string(String) ->
evolve_string(String,?TARGET,?POPULATION,String).
evolve_string(_,_,0,Child) -> Child; evolve_string(Parent,Target,Population,Best_Child) ->
Child = mutate(Parent),
case fitness(Child) < fitness(Best_Child) of
true ->
evolve_string(Parent,Target,Population-1,Child);
false ->
evolve_string(Parent,Target,Population-1,Best_Child)
end.
random_character() ->
case random:uniform(27)-1 of
26 -> $ ;
R -> $A+R
end.
random_string(Length) -> random_string(Length,[]). random_string(0,Acc) -> Acc; random_string(N,Acc) when N > 0 ->
random_string(N-1,[random_character()|Acc]).
</lang>
Euphoria
<lang euphoria>constant table = "ABCDEFGHIJKLMNOPQRSTUVWXYZ " function random_generation(integer len)
sequence s
s = rand(repeat(length(table),len))
for i = 1 to len do
s[i] = table[s[i]]
end for
return s
end function
function mutate(sequence s, integer n)
for i = 1 to length(s) do
if rand(n) = 1 then
s[i] = table[rand(length(table))]
end if
end for
return s
end function
function fitness(sequence probe, sequence target)
atom sum
sum = 0
for i = 1 to length(target) do
sum += power(find(target[i], table) - find(probe[i], table), 2)
end for
return sqrt(sum/length(target))
end function
constant target = "METHINKS IT IS LIKE A WEASEL", C = 30, MUTATE = 15 sequence parent, specimen integer iter, best atom fit, best_fit parent = random_generation(length(target)) iter = 0 while not equal(parent,target) do
best_fit = fitness(parent, target)
printf(1,"Iteration: %3d, \"%s\", deviation %g\n", {iter, parent, best_fit})
specimen = repeat(parent,C+1)
best = C+1
for i = 1 to C do
specimen[i] = mutate(specimen[i], MUTATE)
fit = fitness(specimen[i], target)
if fit < best_fit then
best_fit = fit
best = i
end if
end for
parent = specimen[best]
iter += 1
end while printf(1,"Finally, \"%s\"\n",{parent})</lang>
Output:
Iteration: 0, "HRGPWKOOARZL KTJEBPUYPTOLGDK", deviation 11.1002 Iteration: 1, "HRGPWKOOWRZLLKTJEBPUYPTOLGDK", deviation 9.40175 Iteration: 2, "HRGPOKOOWRZVLKTJEBPUYPTOLGDK", deviation 8.69113 Iteration: 3, "HRKPOKOOWRZVLKTJEBPUDPTOLGDB", deviation 7.46181 Iteration: 4, "HEKPOKOOWRZVLKTJEBPUDPTOLGDB", deviation 7.04577 Iteration: 5, "HEKPOKOOWRZVLKTJEBEUDPTOLGDB", deviation 6.73212 Iteration: 6, "HEKPOKOOWRZVLKTJEBEUDPTALGDB", deviation 6.50549 Iteration: 7, "HEKPOKOOWIZVLKTJEBEUDPTALGDB", deviation 6.27922 Iteration: 8, "HESPOKOOWIZVLKTJEBEUDPTALJDB", deviation 5.85845 Iteration: 9, "HESPOKOOWIZVLKTJEBEUIPTALJDJ", deviation 5.73212 ... Iteration: 201, "METHINKS IT IT LIKE A WEASEL", deviation 0.188982 Iteration: 202, "METHINKS IT IT LIKE A WEASEL", deviation 0.188982 Iteration: 203, "METHINKS IT IT LIKE A WEASEL", deviation 0.188982 Iteration: 204, "METHINKS IT IT LIKE A WEASEL", deviation 0.188982 Iteration: 205, "METHINKS IT IT LIKE A WEASEL", deviation 0.188982 Iteration: 206, "METHINKS IT IT LIKE A WEASEL", deviation 0.188982 Iteration: 207, "METHINKS IT IT LIKE A WEASEL", deviation 0.188982 Iteration: 208, "METHINKS IT IT LIKE A WEASEL", deviation 0.188982 Iteration: 209, "METHINKS IT IT LIKE A WEASEL", deviation 0.188982 Iteration: 210, "METHINKS IT IT LIKE A WEASEL", deviation 0.188982 Finally, "METHINKS IT IS LIKE A WEASEL"
F#
<lang fsharp> //A functional implementation of Evolutionary algorithm //Nigel Galloway February 7th., 2018 let G=System.Random 23 let fitness n=Array.fold2(fun a n g->if n=g then a else a+1) 0 n ("METHINKS IT IS LIKE A WEASEL".ToCharArray()) let alphabet="QWERTYUIOPASDFGHJKLZXCVBNM ".ToCharArray() let mutate (n:char[]) g=Array.iter(fun g->n.[g]<-alphabet.[G.Next()%27]) (Array.init g (fun _->G.Next()%(Array.length n)));n let nextParent n g=List.init 500 (fun _->mutate (Array.copy n) g)|>List.minBy fitness let evolution n=let rec evolution n g=match fitness n with |0->(0,n)::g |l->evolution (nextParent n ((l/2)+1)) ((l,n)::g)
evolution n []
let n = evolution (Array.init 28 (fun _->alphabet.[G.Next()%27]))
</lang>
Real: 00:00:00.021, CPU: 00:00:00.050, GC gen0: 1, gen1: 0
Length of n (37) is the number of generations including the original parent as follows:
Length of n (37) is the number of generations including the original parent as follows: (28, [|' '; 'V'; 'L'; 'D'; 'N'; 'Q'; 'A'; 'Z'; 'P'; 'A'; 'J'; 'A'; 'T'; 'C'; 'S'; 'I'; 'G'; 'H'; 'M'; 'Q'; 'M'; 'J'; 'Y'; 'L'; 'Q'; 'H'; 'S'; 'A'|]) (25, [|'D'; 'V'; 'L'; 'B'; 'N'; 'S'; 'A'; 'Z'; 'B'; 'A'; 'J'; 'Y'; 'T'; 'M'; 'U'; 'L'; 'G'; 'M'; 'M'; 'Q'; 'M'; ' '; 'Y'; 'L'; 'Q'; S'; 'X'; 'Y'|]) (23, [|'V'; 'E'; 'L'; 'A'; 'N'; 'S'; 'A'; 'Z'; 'P'; 'A'; 'J'; ' '; 'T'; 'M'; 'L'; 'L'; 'G'; 'D'; 'M'; 'Z'; 'S'; ' '; 'A'; 'L'; 'L'; 'S'; 'X'; 'Y'|]) (21, [|'V'; 'S'; 'L'; 'J'; 'N'; 'S'; 'A'; 'S'; 'P'; 'A'; 'J'; ' '; ' '; 'M'; 'L'; 'L'; 'G'; 'D'; 'E'; 'I'; 'A'; ' '; 'A'; 'L'; 'L'; 'S'; 'X'; 'Y'|]) (20, [|'V'; 'S'; 'E'; 'H'; 'N'; ' '; 'A'; 'S'; 'P'; 'S'; 'J'; ' '; 'Z'; 'P'; 'L'; 'L'; 'G'; 'B'; 'E'; 'Y'; 'A'; ' '; 'D'; 'H'; 'V'; 'S'; 'X'; 'Y'|]) (18, [|'V'; 'S'; 'K'; 'H'; 'N'; ' '; 'K'; 'S'; 'M'; 'S'; 'J'; ' '; 'I'; 'P'; 'V'; 'L'; 'D'; 'B'; 'E'; 'Y'; 'A'; ' '; 'X'; 'J'; 'V'; 'S'; 'X'; 'Y'|]) (16, [|'W'; 'S'; 'K'; 'H'; 'N'; ' '; 'K'; 'S'; 'M'; 'S'; 'D'; ' '; 'I'; 'S'; 'V'; 'L'; 'D'; 'T'; 'E'; ' '; 'A'; ' '; 'C'; 'J'; 'V'; 'S'; 'W'; 'Y'|]) (14, [|'W'; 'E'; 'K'; 'H'; 'X'; 'G'; 'K'; 'S'; 'M'; 'H'; 'D'; ' '; 'I'; 'S'; 'V'; 'L'; ' '; 'T'; 'E'; ' '; 'A'; ' '; 'C'; 'J'; 'R'; 'S'; 'W'; 'L'|]) (14, [|'W'; 'E'; 'E'; 'H'; 'I'; 'L'; 'K'; 'S'; 'M'; 'H'; 'D'; 'W'; 'I'; 'S'; 'O'; 'L'; 'M'; 'A'; 'E'; ' '; 'A'; ' '; 'Q'; 'J'; 'R'; 'S'; 'W'; 'L'|]) (13, [|'W'; 'E'; 'E'; 'H'; 'I'; 'L'; 'K'; 'S'; 'M'; 'H'; 'D'; 'W'; 'I'; 'S'; 'R'; 'L'; 'S'; 'A'; 'E'; ' '; 'A'; ' '; 'Q'; 'J'; 'Z'; 'S'; 'E'; 'L'|]) (12, [|'W'; 'E'; 'E'; 'H'; 'I'; 'L'; 'K'; 'S'; 'M'; 'H'; 'D'; 'O'; 'I'; 'S'; 'C'; 'L'; 'I'; 'Y'; 'E'; ' '; 'A'; ' '; 'J'; 'O'; 'R'; 'S'; 'E'; 'L'|]) (10, [|'B'; 'E'; 'A'; 'H'; 'I'; 'N'; 'K'; 'S'; 'M'; 'C'; 'T'; 'O'; 'I'; 'S'; 'C'; 'L'; 'I'; 'R'; 'E'; ' '; 'A'; ' '; 'J'; 'O'; 'R'; 'S'; 'E'; 'L'|]) (9, [|'M'; 'E'; 'A'; 'H'; 'I'; 'N'; 'K'; 'S'; 'N'; 'C'; 'T'; 'F'; 'I'; 'S'; 'C'; 'L'; 'I'; 'R'; 'E'; ' '; 'A'; ' '; 'K'; 'N'; 'R'; 'S'; 'E'; 'L'|]) (9, [|'M'; 'E'; 'A'; 'H'; 'I'; 'N'; 'K'; 'S'; 'T'; 'P'; 'T'; 'F'; 'I'; 'S'; 'C'; 'L'; 'I'; 'R'; 'E'; ' '; 'A'; ' '; 'K'; 'N'; 'P'; 'S'; 'E'; 'L'|]) (8, [|'M'; 'E'; 'N'; 'H'; 'I'; 'N'; 'K'; 'S'; 'L'; 'P'; 'T'; 'F'; 'I'; 'S'; 'Y'; 'L'; 'I'; 'K'; 'E'; ' '; 'A'; ' '; 'K'; 'H'; 'P'; 'S'; 'E'; 'L'|]) (8, [|'M'; 'E'; 'N'; 'H'; 'I'; 'N'; 'K'; 'S'; 'L'; 'E'; 'T'; 'F'; 'I'; 'R'; 'Y'; 'L'; 'I'; 'K'; 'E'; ' '; 'A'; ' '; 'Q'; 'H'; 'A'; 'S'; 'E'; 'L'|]) (7, [|'M'; 'E'; ' '; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'E'; 'T'; 'F'; 'I'; 'K'; 'Y'; 'L'; 'I'; 'K'; 'E'; ' '; 'A'; ' '; 'Q'; 'H'; 'A'; 'S'; 'E'; 'L'|]) (7, [|'M'; 'E'; ' '; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'E'; 'T'; 'F'; 'I'; 'K'; 'J'; 'L'; 'I'; 'K'; 'E'; ' '; 'A'; ' '; 'Q'; 'H'; 'A'; 'S'; 'E'; 'L'|]) (6, [|'M'; 'E'; 'T'; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'I'; 'T'; 'F'; 'I'; 'K'; 'J'; 'L'; 'I'; 'D'; 'E'; ' '; 'A'; ' '; 'Q'; 'Z'; 'A'; 'S'; 'E'; 'L'|]) (5, [|'M'; 'E'; 'T'; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'E'; 'J'; 'L'; 'I'; 'T'; 'E'; ' '; 'A'; ' '; 'X'; 'Z'; 'A'; 'S'; 'E'; 'L'|]) (5, [|'M'; 'E'; 'T'; 'H'; 'I'; 'F'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; 'I'; 'L'; 'I'; 'T'; 'E'; ' '; 'A'; ' '; 'X'; 'Z'; 'A'; 'S'; 'E'; 'L'|]) (5, [|'M'; 'E'; 'T'; 'H'; 'I'; 'F'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; ' '; 'L'; 'I'; 'T'; 'E'; ' '; 'A'; ' '; 'K'; 'Z'; 'A'; 'Z'; 'E'; 'L'|]) (5, [|'M'; 'E'; 'T'; 'H'; 'I'; 'F'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; ' '; 'L'; 'I'; 'F'; 'E'; ' '; 'A'; ' '; 'K'; 'Z'; 'A'; 'P'; 'E'; 'L'|]) (5, [|'M'; 'E'; 'T'; 'H'; 'I'; 'R'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; ' '; 'L'; 'I'; 'F'; 'E'; ' '; 'A'; ' '; 'K'; 'Z'; 'A'; 'F'; 'E'; 'L'|]) (4, [|'M'; 'E'; 'T'; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; ' '; 'L'; 'I'; 'F'; 'E'; ' '; 'A'; ' '; 'K'; 'Z'; 'A'; 'F'; 'E'; 'L'|]) (3, [|'M'; 'E'; 'T'; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; ' '; 'L'; 'I'; 'J'; 'E'; ' '; 'A'; ' '; 'K'; 'E'; 'A'; 'F'; 'E'; 'L'|]) (3, [|'M'; 'E'; 'T'; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; ' '; 'L'; 'I'; 'J'; 'E'; ' '; 'A'; ' '; 'Y'; 'E'; 'A'; 'F'; 'E'; 'L'|]) (3, [|'M'; 'E'; 'T'; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; ' '; 'L'; 'I'; 'J'; 'E'; ' '; 'A'; ' '; 'K'; 'E'; 'A'; 'G'; 'E'; 'L'|]) (3, [|'M'; 'E'; 'T'; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; ' '; 'L'; 'I'; 'A'; 'E'; ' '; 'A'; ' '; 'K'; 'E'; 'A'; 'G'; 'E'; 'L'|]) (2, [|'M'; 'E'; 'T'; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; ' '; 'L'; 'I'; 'K'; 'E'; ' '; 'A'; ' '; 'K'; 'E'; 'A'; 'Q'; 'E'; 'L'|]) (2, [|'M'; 'E'; 'T'; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; ' '; 'L'; 'I'; 'K'; 'E'; ' '; 'A'; ' '; 'K'; 'E'; 'A'; 'Q'; 'E'; 'L'|]) (2, [|'M'; 'E'; 'T'; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; ' '; 'L'; 'I'; 'K'; 'E'; ' '; 'A'; ' '; 'K'; 'E'; 'A'; 'N'; 'E'; 'L'|]) (1, [|'M'; 'E'; 'T'; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; ' '; 'L'; 'I'; 'K'; 'E'; ' '; 'A'; ' '; 'K'; 'E'; 'A'; 'S'; 'E'; 'L'|]) (1, [|'M'; 'E'; 'T'; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; ' '; 'L'; 'I'; 'K'; 'E'; ' '; 'A'; ' '; 'K'; 'E'; 'A'; 'S'; 'E'; 'L'|]) (1, [|'M'; 'E'; 'T'; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; ' '; 'L'; 'I'; 'K'; 'E'; ' '; 'A'; ' '; 'N'; 'E'; 'A'; 'S'; 'E'; 'L'|]) (1, [|'M'; 'E'; 'T'; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; ' '; 'L'; 'I'; 'K'; 'E'; ' '; 'A'; ' '; 'H'; 'E'; 'A'; 'S'; 'E'; 'L'|]) (0, [|'M'; 'E'; 'T'; 'H'; 'I'; 'N'; 'K'; 'S'; ' '; 'I'; 'T'; ' '; 'I'; 'S'; ' '; 'L'; 'I'; 'K'; 'E'; ' '; 'A'; ' '; 'W'; 'E'; 'A'; 'S'; 'E'; 'L'|])
Factor
<lang factor>USING: arrays formatting io kernel literals math prettyprint random sequences strings ; FROM: math.extras => ... ; IN: rosetta-code.evolutionary-algorithm
CONSTANT: target "METHINKS IT IS LIKE A WEASEL" CONSTANT: mutation-rate 0.1 CONSTANT: num-children 25 CONSTANT: valid-chars
$[ CHAR: A ... CHAR: Z >array { 32 } append ]
- rand-char ( -- n )
valid-chars random ;
- new-parent ( -- str )
target length [ rand-char ] replicate >string ;
- fitness ( str -- n )
target [ = ] { } 2map-as sift length ;
- mutate ( str rate -- str/str' )
[ random-unit > [ drop rand-char ] when ] curry map ;
- next-parent ( str -- str/str' )
dup [ mutation-rate mutate ] curry num-children 1 - swap replicate [ 1array ] dip append [ fitness ] supremum-by ;
- print-parent ( str -- )
[ fitness pprint bl ] [ print ] bi ;
- main ( -- )
0 new-parent [ dup target = ] [ next-parent dup print-parent [ 1 + ] dip ] until drop "Finished in %d generations." printf ;
MAIN: main</lang>
- Output:
1 JWTBPZMHKOFFWDSBCLZUCFUAWUJ 2 JWTAPFMSKOFFWDSBCLZUCHUAWUJ 3 JWTAPSOSKOFFWDOBFLZ CHGAWUJ ... 14 MWTTISKS EFFWS LIKE JZGAWBKL ... 28 METHINKS IT IS LIKE A WEASEL Finished in 298 generations.
Fantom
<lang fantom> class Main {
static const Str target := "METHINKS IT IS LIKE A WEASEL"
static const Int C := 100 // size of population
static const Float p := 0.1f // chance any char is mutated
// compute distance of str from target
static Int fitness (Str str)
{
Int sum := 0
str.each |Int c, Int index|
{
if (c != target[index]) sum += 1
}
return sum
}
// mutate given parent string
static Str mutate (Str str)
{
Str result := ""
str.size.times |Int index|
{
result += ((Float.random < p) ? randomChar() : str[index]).toChar
}
return result
}
// return a random char
static Int randomChar ()
{
"ABCDEFGHIJKLMNOPQRSTUVWXYZ "[Int.random(0..26)]
}
// make population by mutating parent and sorting by fitness
static Str[] makePopulation (Str parent)
{
Str[] result := [,]
C.times { result.add (mutate(parent)) }
result.sort |Str a, Str b -> Int| { fitness(a) <=> fitness(b) }
return result
}
public static Void main ()
{
Str parent := ""
target.size.times { parent += randomChar().toChar }
while (parent != target)
{
echo (parent)
parent = makePopulation(parent).first
}
echo (parent)
}
} </lang>
Forth
<lang forth>include lib/choose.4th
\ target string
s" METHINKS IT IS LIKE A WEASEL" sconstant target
27 constant /charset \ size of characterset 29 constant /target \ size of target string 32 constant #copies \ number of offspring
/target string charset \ characterset /target string this-generation \ current generation and offspring /target #copies [*] string new-generation
- this new-generation does> swap /target chars * + ;
\ generate a mutation
- mutation charset /charset choose chars + c@ ;
\ print the current candidate
- .candidate ( n1 n2 -- n1 f)
." Generation " over 2 .r ." : " this-generation count type cr /target -1 [+] =
- \ test a candidate on
\ THE NUMBER of correct genes
- test-candidate ( a -- a n)
dup target 0 >r >r ( a1 a2) begin ( a1 a2) r@ ( a1 a2 n) while ( a1 a2) over c@ over c@ = ( a1 a2 n) r> r> rot if 1+ then >r 1- >r ( a1 a2) char+ swap char+ swap ( a1+1 a2+1) repeat ( a1+1 a2+1) drop drop r> drop r> ( a n)
\ find the best candidate
- get-candidate ( -- n)
#copies 0 >r >r ( --) begin ( --) r@ ( n) while ( --) r@ 1- new-generation ( a) test-candidate r'@ over < ( a n f) if swap count this-generation place r> 1- swap r> drop >r >r else drop drop r> 1- >r then ( --) repeat ( --) r> drop r> ( n)
\ generate a new candidate
- make-candidate ( a --)
dup charset count rot place ( a1) this-generation target >r ( a1 a2 a3) begin ( a1 a2 a3) r@ ( a1 a2 a3 n) while ( a1 a2 a3) over c@ over c@ = ( a1 a2 a3 f) swap >r >r over r> ( a1 a2 a1 f) if over c@ else mutation then ( a1 a2 a1 c) swap c! r> r> 1- >r ( a1 a2 a3) char+ rot char+ rot char+ rot ( a1+1 a2+1 a3+1) repeat ( a1+1 a2+1 a3+1) drop drop drop r> drop ( --)
\ make a whole new generation
- make-generation #copies 0 do i new-generation make-candidate loop ;
\ weasel program
- weasel
s" ABCDEFGHIJKLMNOPQRSTUVWXYZ " 2dup charset place \ initialize the characterset this-generation place 0 \ initialize the first generation begin \ start the program 1+ make-generation \ make a new generation get-candidate .candidate \ select the best candidate until drop \ stop when we've found perfection
weasel</lang> Output:
habe@linux-471m:~> 4th cxq weasel1.4th Generation 1: MUPHMOOXEIBGELPUZZEGXIVMELFL Generation 2: MUBHIYDPKIQWYXSVLUEBH TYJMRL Generation 3: MEVHIUTZDIVQSMRT KEDP GURBSL Generation 4: MEWHIHKPKITBWSYVYKEXZ ASBAL Generation 5: MEVHIPKMRIT VSTSBKE R YNJWEL Generation 6: MERHIIKQ IT OSNEUKE A TKCLEL Generation 7: METHINKO IT SXREKE A JDAIEL Generation 8: METHINKS IT SSSVIKE A OIA EL Generation 9: METHINKS IT ISICIKE A IGASEL Generation 10: METHINKS IT ISITIKE A WZASEL Generation 11: METHINKS IT ISACIKE A WEASEL Generation 12: METHINKS IT ISKLIKE A WEASEL Generation 13: METHINKS IT IS LIKE A WEASEL
Fortran
<lang fortran>
!*************************************************************************************************** module evolve_routines !*************************************************************************************************** implicit none !the target string: character(len=*),parameter :: targ = 'METHINKS IT IS LIKE A WEASEL' contains !*************************************************************************************************** !******************************************************************** pure elemental function fitness(member) result(n) !******************************************************************** ! The fitness function. The lower the value, the better the match. ! It is zero if they are identical. !******************************************************************** implicit none integer :: n character(len=*),intent(in) :: member integer :: i n=0 do i=1,len(targ) n = n + abs( ichar(targ(i:i)) - ichar(member(i:i)) ) end do !******************************************************************** end function fitness !******************************************************************** !******************************************************************** pure elemental subroutine mutate(member,factor) !******************************************************************** ! mutate a member of the population. !******************************************************************** implicit none character(len=*),intent(inout) :: member !population member real,intent(in) :: factor !mutation factor integer,parameter :: n_chars = 27 !number of characters in set character(len=n_chars),parameter :: chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ ' real :: rnd_val integer :: i,j,n n = len(member) do i=1,n rnd_val = rand() if (rnd_val<=factor) then !mutate this element rnd_val = rand() j = int(rnd_val*n_chars)+1 !an integer between 1 and n_chars member(i:i) = chars(j:j) end if end do !********************************************************************
end subroutine mutate
!********************************************************************
!*************************************************************************************************** end module evolve_routines !*************************************************************************************************** !*************************************************************************************************** program evolve !*************************************************************************************************** ! The main program !*************************************************************************************************** use evolve_routines implicit none !Tuning parameters: integer,parameter :: seed = 12345 !random number generator seed integer,parameter :: max_iter = 10000 !maximum number of iterations integer,parameter :: population_size = 200 !size of the population real,parameter :: factor = 0.04 ![0,1] mutation factor integer,parameter :: iprint = 5 !print every iprint iterations !local variables: integer :: i,iter integer,dimension(1) :: i_best character(len=len(targ)),dimension(population_size) :: population !initialize random number generator: call srand(seed) !create initial population: ! [the first element of the population will hold the best member] population(1) = 'PACQXJB CQPWEYKSVDCIOUPKUOJY' !initial guess iter=0 write(*,'(A10,A30,A10)') 'iter','best','fitness' write(*,'(I10,A30,I10)') iter,population(1),fitness(population(1)) do iter = iter + 1 !iteration counter !write the iteration: if (mod(iter,iprint)==0) write(*,'(I10,A30,I10)') iter,population(1),fitness(population(1))
!check exit conditions: if ( iter>max_iter .or. fitness(population(1))==0 ) exit !copy best member and mutate: population = population(1) do i=2,population_size call mutate(population(i),factor) end do !select the new best population member: ! [the best has the lowest value] i_best = minloc(fitness(population)) population(1) = population(i_best(1)) end do !write the last iteration: if (mod(iter,iprint)/=0) write(*,'(I10,A30,I10)') iter,population(1),fitness(population(1)) if (iter>max_iter) then write(*,*) 'No solution found.' else write(*,*) 'Solution found.' end if !*************************************************************************************************** end program evolve !***************************************************************************************************
</lang>
The output is:
<lang>
iter best fitness
0 PACQXJB CQPWEYKSVDCIOUPKUOJY 459
5 PACDXJBRCQP EYKSVDK OAPKGOJY 278
10 PAPDJJBOCQP EYCDKDK A PHGQJF 177
15 PAUDJJBO FP FY VKBL A PEGQJF 100
20 PEUDJMOO KP FY IKLD A YECQJF 57
25 PEUHJMOT KU FS IKLD A YECQJL 35
30 PEUHJMIT KU GS LKJD A YEAQFL 23
35 MERHJMIT KT IS LHJD A YEASFL 15
40 MERHJMKS IT IS LIJD A WEASFL 7
45 MERHINKS IT IS LIJD A WEASFL 5
50 MERHINKS IT IS LIJD A WEASEL 4
55 MERHINKS IT IS LIKD A WEASEL 3
60 MESHINKS IT IS LIKD A WEASEL 2
65 MESHINKS IT IS LIKD A WEASEL 2
70 MESHINKS IT IS LIKE A WEASEL 1
75 METHINKS IT IS LIKE A WEASEL 0
</lang>
FreeBASIC
<lang freebasic>' version 01-07-2018 ' compile with: fbc -s console
Randomize Timer Const As UInteger children = 100 Const As Double mutate_rate = 0.05
Function fitness(target As String, tmp As String) As UInteger
Dim As UInteger x, f
For x = 0 To Len(tmp) -1
If tmp[x] = target[x] Then f += 1
Next
Return f
End Function
Sub mutate(tmp As String, chars As String, mute_rate As Double)
If Rnd <= mute_rate Then
tmp[Int(Rnd * Len(tmp))] = chars[Int(Rnd * Len(chars))]
End If
End Sub
' ------=< MAIN >=------
Dim As String target = "METHINKS IT IS LIKE A WEASEL" Dim As String chars = " ABCDEFGHIJKLMNOPQRSTUVWXYZ" Dim As String parent, mutation() Dim As UInteger x, iter, f, fit(), best_fit, parent_fit
For x = 1 To Len(target)
parent += Chr(chars[Int(Rnd * Len(chars))])
Next
f = fitness(target, parent) parent_fit = f best_fit = f
Print "iteration best fit Parent" Print "========= ======== ============================" Print Using " #### #### ";iter; best_fit; Print parent
Do
iter += 1 ReDim mutation(1 To children),fit(1 To children)
For x = 1 To children
mutation(x) = parent
mutate(mutation(x), chars, mutate_rate)
Next
For x = 1 To children
If mutation(x) <> parent Then
f = fitness(target, mutation(x))
If best_fit < f Then
best_fit = f
fit(x) = f
Else
fit(x) = parent_fit
End If
End If
Next
If best_fit > parent_fit Then
For x = 1 To children
If fit(x) = best_fit Then
parent = mutation(x)
Print Using " #### #### ";iter; best_fit;
Print parent
End If
Next
End If
Loop Until parent = target
' empty keyboard buffer While InKey <> "" : Wend Print : Print "hit any key to end program" Sleep End</lang>
- Output:
iteration best fit Parent
========= ======== ============================
0 2 VDHQATVSHHSVRFNAPFEGZARZGCZE
3 3 VEHQATVSHHSVRFNAPFEGZARZGCZE
5 4 VEHQATVSHHSVRFNAPFEGZAREGCZE
11 5 VEHQATKSHHSVRFNAPFEGZAREGCZE
19 6 VEHQATKSHHSVRFNAPFEGZAREGSZE
32 7 VEHQANKSHHSVRFNAPFEGZAREGSZE
36 8 VEHQANKSHHSVRFNAPFEGAAREGSZE
38 9 VEHQANKSHHTVRFNAPFEGAAREGSZE
39 10 VEHQANKSHHTVRFNAPFEGAAREGSEE
48 11 VEHHANKSHHTVRFNAPFEGAAREGSEE
53 12 VEHHANKSHITVRFNAPFEGAAREGSEE
73 13 VEHHINKSHITVRFNAPFEGAAREGSEE
81 14 VEHHINKSHITVRFNAPFEGAAWEGSEE
95 15 VEHHINKSHITVIFNAPFEGAAWEGSEE
96 16 VEHHINKSHITVIFNLPFEGAAWEGSEE
135 17 VETHINKSHITVIFNLPFEGAAWEGSEE
137 18 VETHINKSHITVISNLPFEGAAWEGSEE
152 19 VETHINKSHITVISNLPKEGAAWEGSEE
171 20 VETHINKSHITVISNLPKEGAAWEGSEL
174 21 VETHINKSHITVIS LPKEGAAWEGSEL
188 22 VETHINKSHITVIS LIKEGAAWEGSEL
213 23 VETHINKSHIT IS LIKEGAAWEGSEL
220 24 METHINKSHIT IS LIKEGAAWEGSEL
374 25 METHINKSHIT IS LIKE AAWEGSEL
378 26 METHINKSHIT IS LIKE A WEGSEL
555 27 METHINKS IT IS LIKE A WEGSEL
585 28 METHINKS IT IS LIKE A WEASEL
Fōrmulæ
Fōrmulæ programs are not textual, visualization/edition of programs is done showing/manipulating structures but not text. Moreover, there can be multiple visual representations of the same program. Even though it is possible to have textual representation —i.e. XML, JSON— they are intended for storage and transfer purposes more than visualization and edition.
Programs in Fōrmulæ are created/edited online in its website, However they run on execution servers. By default remote servers are used, but they are limited in memory and processing power, since they are intended for demonstration and casual use. A local server can be downloaded and installed, it has no limitations (it runs in your own computer). Because of that, example programs can be fully visualized and edited, but some of them will not run if they require a moderate or heavy computation/memory resources, and no local server is being used.
In this page you can see the program(s) related to this task and their results.
Go
I took the liberty to use []byte for the "strings" mentioned in the task description. Go has a native string type, but in this case it was both easier and more efficient to work with byte slices and just convert to string when there was something to print.
<lang go>package main
import (
"fmt" "math/rand" "time"
)
var target = []byte("METHINKS IT IS LIKE A WEASEL") var set = []byte("ABCDEFGHIJKLMNOPQRSTUVWXYZ ") var parent []byte
func init() {
rand.Seed(time.Now().UnixNano())
parent = make([]byte, len(target))
for i := range parent {
parent[i] = set[rand.Intn(len(set))]
}
}
// fitness: 0 is perfect fit. greater numbers indicate worse fit. func fitness(a []byte) (h int) {
// (hamming distance)
for i, tc := range target {
if a[i] != tc {
h++
}
}
return
}
// set m to mutation of p, with each character of p mutated with probability r func mutate(p, m []byte, r float64) {
for i, ch := range p {
if rand.Float64() < r {
m[i] = set[rand.Intn(len(set))]
} else {
m[i] = ch
}
}
}
func main() {
const c = 20 // number of times to copy and mutate parent
copies := make([][]byte, c)
for i := range copies {
copies[i] = make([]byte, len(parent))
}
fmt.Println(string(parent))
for best := fitness(parent); best > 0; {
for _, cp := range copies {
mutate(parent, cp, .05)
}
for _, cp := range copies {
fm := fitness(cp)
if fm < best {
best = fm
copy(parent, cp)
fmt.Println(string(parent))
}
}
}
}</lang>
- Output:
HRVDKMXETOIOVSFMVHWKIY ZDXEY HRVDKMXE OIOVSFMVHWKIY ZDWEY HRVDKMXE OIOISFMVHWVIY ZDSEY HRVDKMXE OIOISFMFHWVI ZDSEL HRVDKMXE OIOISFLFHWVI ZDSEL HRVDKMXE OIOISFLFHWVI ZASEL HRVDKMXS OIOISFLFHWVI ZASEL HRVHKMXS OIOISFLHHWVI ZASEL MRVHKMXS OHOISFLHHWVI ZASEL MRVHKMXS OTOISFLHHWVI FASEL MRVHKNXS OTOISFLHHWVI FASEL MRVHKNXS OTOISFLHHWVI EASEL MEVHKNXS OTOISFLHHWVI IEASEL MEVHKNXS OTOISFLHHWVI WEASEL METHKNXS OTOISFLHHWVI WEASEL METHKNXS ZTOIS LHHWVI WEASEL METHKNKS ZTOIS LHHWVI WEASEL METHKNKS ZTOIS LHKWEI WEASEL METHKNKS ZT IS LHKWEI WEASEL METHKNKS ZT IS LHKEEI WEASEL METHKNKS ZT IS LHKEEA WEASEL METHKNKS ZT IS LHKE A WEASEL METHKNKS ZT IS LIKE A WEASEL METHINKS ZT IS LIKE A WEASEL METHINKS IT IS LIKE A WEASEL
Haskell
<lang Haskell>import System.Random import Control.Monad import Data.List import Data.Ord import Data.Array
showNum :: (Num a, Show a) => Int -> a -> String showNum w = until ((>w-1).length) (' ':) . show
replace :: Int -> a -> [a] -> [a] replace n c ls = take (n-1) ls ++ [c] ++ drop n ls
target = "METHINKS IT IS LIKE A WEASEL" pfit = length target mutateRate = 20 popsize = 100 charSet = listArray (0,26) $ ' ': ['A'..'Z'] :: Array Int Char
fitness = length . filter id . zipWith (==) target
printRes i g = putStrLn $
"gen:" ++ showNum 4 i ++ " "
++ "fitn:" ++ showNum 4 (round $ 100 * fromIntegral s / fromIntegral pfit ) ++ "% "
++ show g
where s = fitness g
mutate :: [Char] -> Int -> IO [Char] mutate g mr = do
let r = length g chances <- replicateM r $ randomRIO (1,mr) let pos = elemIndices 1 chances chrs <- replicateM (length pos) $ randomRIO (bounds charSet) let nchrs = map (charSet!) chrs return $ foldl (\ng (p,c) -> replace (p+1) c ng) g (zip pos nchrs)
evolve :: [Char] -> Int -> Int -> IO () evolve parent gen mr = do
when ((gen-1) `mod` 20 == 0) $ printRes (gen-1) parent
children <- replicateM popsize (mutate parent mr)
let child = maximumBy (comparing fitness) (parent:children)
if fitness child == pfit then printRes gen child
else evolve child (succ gen) mr
main = do
let r = length target genes <- replicateM r $ randomRIO (bounds charSet) let parent = map (charSet!) genes evolve parent 1 mutateRate</lang>
Example run in GHCi:
*Main> main gen: 0 fitn: 4% "AICJEWXYSFTMOAYOHNFZ HSLFNBY" gen: 20 fitn: 54% "XZTHIWXSSVTMSUYOIKEZA WEFSEL" gen: 40 fitn: 89% "METHINXSSIT IS OIKE A WEASEL" gen: 60 fitn: 93% "METHINXSSIT IS LIKE A WEASEL" gen: 78 fitn: 100% "METHINKS IT IS LIKE A WEASEL"
Alternate Presentation
I find this easier to read.
<lang Haskell>import System.Random import Data.List import Data.Ord import Data.Array import Control.Monad import Control.Arrow
target = "METHINKS IT IS LIKE A WEASEL" mutateRate = 0.1 popSize = 100 printEvery = 10
alphabet = listArray (0,26) (' ':['A'..'Z'])
randomChar = (randomRIO (0,26) :: IO Int) >>= return . (alphabet !)
origin = mapM createChar target
where createChar c = randomChar
fitness = length . filter id . zipWith (==) target
mutate = mapM mutateChar
where mutateChar c = do
r <- randomRIO (0.0,1.0) :: IO Double
if r < mutateRate then randomChar else return c
converge n parent = do
if n`mod`printEvery == 0 then putStrLn fmtd else return ()
if target == parent
then putStrLn $ "\nFinal: " ++ fmtd
else mapM mutate (replicate (popSize-1) parent) >>=
converge (n+1) . fst . maximumBy (comparing snd) . map (id &&& fitness) . (parent:)
where fmtd = parent ++ ": " ++ show (fitness parent) ++ " (" ++ show n ++ ")"
main = origin >>= converge 0</lang> Example:
YUZVNNZ SXPSNGZFRHZKVDOEPIGS: 2 (0) BEZHANK KIPONSYSPKV F AEULEC: 11 (10) BETHANKSFIT ISYHIKJ I TERLER: 17 (20) METHINKS IT IS YIKE R TERYER: 22 (30) METHINKS IT IS YIKE WEASEQ: 25 (40) METHINKS IT IS MIKE WEASEI: 25 (50) METHINKS IT IS LIKE D WEASEI: 26 (60) METHINKS IT IS LIKE T WEASEX: 26 (70) METHINKS IT IS LIKE I WEASEL: 27 (80) Final: METHINKS IT IS LIKE A WEASEL: 28 (86)
Icon and Unicon
<lang icon>global target, chars, parent, C, M, current_fitness
procedure fitness(s) fit := 0 #Increment the fitness for every position in the string s that matches the target every i := 1 to *target & s[i] == target[i] do fit +:= 1 return fit end
procedure mutate(s) #If a random number between 0 and 1 is inside the bounds of mutation randomly alter a character in the string if (?0 <= M) then ?s := ?chars return s end
procedure generation() population := [ ] next_parent := "" next_fitness := -1
#Create the next population every 1 to C do push(population, mutate(parent)) #Find the member of the population with highest fitness, or use the last one inspected every x := !population & (xf := fitness(x)) > next_fitness do { next_parent := x next_fitness := xf }
parent := next_parent
return next_fitness end
procedure main() target := "METHINKS IT IS LIKE A WEASEL" #Our target string chars := &ucase ++ " " #Set of usable characters parent := "" & every 1 to *target do parent ||:= ?chars #The universal common ancestor! current_fitness := fitness(parent) #The best fitness we have so far
C := 50 #Population size in each generation
M := 0.5 #Mutation rate per individual in a generation
gen := 1 #Until current fitness reaches a score of perfect match with the target string keep generating new populations until ((current_fitness := generation()) = *target) do {
write(gen || " " || current_fitness || " " || parent)
gen +:= 1
} write("At generation " || gen || " we found a string with perfect fitness at " || current_fitness || " reading: " || parent) end </lang>
J
Solution:
Using sum of differences from the target for fitness, i.e. 0 is optimal fitness.
<lang j>CHARSET=: 'ABCDEFGHIJKLMNOPQRSTUVWXYZ '
NPROG=: 100 NB. number of progeny (C)
MRATE=: 0.05 NB. mutation rate
create =: (?@$&$ { ])&CHARSET NB. creates random list from charset of same shape as y fitness =: +/@:~:"1 copy =: # ,: mutate =: &(>: $ ?@$ 0:)(`(,: create))} NB. adverb select =: ] {~ (i. <./)@:fitness NB. select fittest member of population
nextgen =: select ] , [: MRATE mutate NPROG copy ] while =: conjunction def '(] , (u {:))^:(v {:)^:_ ,:'
evolve=: nextgen while (0 < fitness) create</lang>
Example usage:
Returns list of best solutions at each generation until converged.
<lang j> filter=: {: ,~ ({~ i.@>.&.(%&20)@#) NB. take every 20th and last item
filter evolve 'METHINKS IT IS LIKE A WEASEL'
XXURVQXKQXDLCGFVICCUA NUQPND MEFHINVQQXT IW LIKEUA WEAPEL METHINVS IT IW LIKEUA WEAPEL METHINKS IT IS LIKE A WEASEL</lang>
Alternative solution:
Using explicit versions of mutate and evolve above.
<lang j>CHARSET=: 'ABCDEFGHIJKLMNOPQRSTUVWXYZ '
NPROG=: 100 NB. "C" from specification
fitness=: +/@:~:"1 select=: ] {~ (i. <./)@:fitness NB. select fittest member of population populate=: (?@$&# { ])&CHARSET NB. get random list from charset of same length as y log=: [: smoutput [: ;:inv (('#';'fitness: ';'; ') ,&.> ":&.>)
mutate=: dyad define
idxmut=. I. x >: (*/$y) ?@$ 0 (populate idxmut) idxmut"_} y
)
evolve=: monad define
target=. y parent=. populate y iter=. 0 mrate=. %#y while. 0 < val=. target fitness parent do. if. 0 = 50|iter do. log iter;val;parent end. iter=. iter + 1 progeny=. mrate mutate NPROG # ,: parent NB. create progeny by mutating parent copies parent=. target select parent,progeny NB. select fittest parent for next generation end. log iter;val;parent parent
)</lang>
Example Usage: <lang j> evolve 'METHINKS IT IS LIKE A WEASEL'
- 0 fitness: 27 ; YGFDJFTBEDB FAIJJGMFKDPYELOA
- 50 fitness: 2 ; MEVHINKS IT IS LIKE ADWEASEL
- 76 fitness: 0 ; METHINKS IT IS LIKE A WEASEL
METHINKS IT IS LIKE A WEASEL</lang>
Java
(Close)
<lang java5> import java.util.Random;
public class EvoAlgo {
static final String target = "METHINKS IT IS LIKE A WEASEL"; static final char[] possibilities = "ABCDEFGHIJKLMNOPQRSTUVWXYZ ".toCharArray(); static int C = 100; //number of spawn per generation static double minMutateRate = 0.09; static int perfectFitness = target.length(); private static String parent; static Random rand = new Random();
private static int fitness(String trial){
int retVal = 0;
for(int i = 0;i < trial.length(); i++){
if (trial.charAt(i) == target.charAt(i)) retVal++;
}
return retVal;
}
private static double newMutateRate(){
return (((double)perfectFitness - fitness(parent)) / perfectFitness * (1 - minMutateRate));
}
private static String mutate(String parent, double rate){
String retVal = "";
for(int i = 0;i < parent.length(); i++){
retVal += (rand.nextDouble() <= rate) ?
possibilities[rand.nextInt(possibilities.length)]:
parent.charAt(i);
}
return retVal;
}
public static void main(String[] args){
parent = mutate(target, 1);
int iter = 0;
while(!target.equals(parent)){
double rate = newMutateRate();
iter++;
if(iter % 100 == 0){
System.out.println(iter +": "+parent+ ", fitness: "+fitness(parent)+", rate: "+rate);
}
String bestSpawn = null;
int bestFit = 0;
for(int i = 0; i < C; i++){
String spawn = mutate(parent, rate);
int fitness = fitness(spawn);
if(fitness > bestFit){
bestSpawn = spawn;
bestFit = fitness;
}
}
parent = bestFit > fitness(parent) ? bestSpawn : parent;
}
System.out.println(parent+", "+iter);
}
}</lang> Output:
100: MEVHIBXSCG TP QIK FZGJ SEL, fitness: 13, rate: 0.4875 200: MEBHINMSVI IHTQIKW FTDEZSWL, fitness: 15, rate: 0.42250000000000004 300: METHINMSMIA IHUFIKA F WEYSEL, fitness: 19, rate: 0.29250000000000004 400: METHINSS IT IQULIKA F WEGSEL, fitness: 22, rate: 0.195 METHINKS IT IS LIKE A WEASEL, 492
JavaScript
Using cross-browser techniques to support Array.reduce and Array.map
<lang javascript>// ------------------------------------- Cross-browser Compatibility -------------------------------------
/* Compatibility code to reduce an array
* Source: https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/Reduce */
if (!Array.prototype.reduce) {
Array.prototype.reduce = function (fun /*, initialValue */ ) {
"use strict";
if (this === void 0 || this === null) throw new TypeError();
var t = Object(this);
var len = t.length >>> 0;
if (typeof fun !== "function") throw new TypeError();
// no value to return if no initial value and an empty array
if (len == 0 && arguments.length == 1) throw new TypeError();
var k = 0;
var accumulator;
if (arguments.length >= 2) {
accumulator = arguments[1];
} else {
do {
if (k in t) {
accumulator = t[k++];
break;
}
// if array contains no values, no initial value to return
if (++k >= len) throw new TypeError();
}
while (true);
}
while (k < len) {
if (k in t) accumulator = fun.call(undefined, accumulator, t[k], k, t);
k++;
}
return accumulator; };
}
/* Compatibility code to map an array
* Source: https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/Map */
if (!Array.prototype.map) {
Array.prototype.map = function (fun /*, thisp */ ) {
"use strict";
if (this === void 0 || this === null) throw new TypeError();
var t = Object(this);
var len = t.length >>> 0;
if (typeof fun !== "function") throw new TypeError();
var res = new Array(len);
var thisp = arguments[1];
for (var i = 0; i < len; i++) {
if (i in t) res[i] = fun.call(thisp, t[i], i, t);
}
return res; };
}
/* ------------------------------------- Generator -------------------------------------
* Generates a fixed length gene sequence via a gene strategy object. * The gene strategy object must have two functions: * - "create": returns create a new gene * - "mutate(existingGene)": returns mutation of an existing gene */
function Generator(length, mutationRate, geneStrategy) {
this.size = length; this.mutationRate = mutationRate; this.geneStrategy = geneStrategy;
}
Generator.prototype.spawn = function () {
var genes = [],
x;
for (x = 0; x < this.size; x += 1) {
genes.push(this.geneStrategy.create());
}
return genes;
};
Generator.prototype.mutate = function (parent) {
return parent.map(function (char) {
if (Math.random() > this.mutationRate) {
return char;
}
return this.geneStrategy.mutate(char);
}, this);
};
/* ------------------------------------- Population -------------------------------------
* Helper class that holds and spawns a new population. */
function Population(size, generator) {
this.size = size; this.generator = generator;
this.population = [];
// Build initial popuation;
for (var x = 0; x < this.size; x += 1) {
this.population.push(this.generator.spawn());
}
}
Population.prototype.spawn = function (parent) {
this.population = [];
for (var x = 0; x < this.size; x += 1) {
this.population.push(this.generator.mutate(parent));
}
};
/* ------------------------------------- Evolver -------------------------------------
* Attempts to converge a population based a fitness strategy object. * The fitness strategy object must have three function * - "score(individual)": returns a score for an individual. * - "compare(scoreA, scoreB)": return true if scoreA is better (ie more fit) then scoreB * - "done( score )": return true if score is acceptable (ie we have successfully converged). */
function Evolver(size, generator, fitness) {
this.done = false; this.fitness = fitness; this.population = new Population(size, generator);
}
Evolver.prototype.getFittest = function () {
return this.population.population.reduce(function (best, individual) {
var currentScore = this.fitness.score(individual);
if (best === null || this.fitness.compare(currentScore, best.score)) {
return {
score: currentScore,
individual: individual
};
} else {
return best;
}
}, null);
};
Evolver.prototype.doGeneration = function () {
this.fittest = this.getFittest();
this.done = this.fitness.done(this.fittest.score);
if (!this.done) {
this.population.spawn(this.fittest.individual);
}
};
Evolver.prototype.run = function (onCheckpoint, checkPointFrequency) {
checkPointFrequency = checkPointFrequency || 10; // Default to Checkpoints every 10 generations
var generation = 0;
while (!this.done) {
this.doGeneration();
if (generation % checkPointFrequency === 0) {
onCheckpoint(generation, this.fittest);
}
generation += 1;
}
onCheckpoint(generation, this.fittest);
return this.fittest;
};
// ------------------------------------- Exports ------------------------------------- window.Generator = Generator; window.Evolver = Evolver;
// helper utitlity to combine elements of two arrays.
Array.prototype.zip = function (b, func) {
var result = [],
max = Math.max(this.length, b.length),
x;
for (x = 0; x < max; x += 1) {
result.push(func(this[x], b[x]));
}
return result;
};
var target = "METHINKS IT IS LIKE A WEASEL", geneStrategy, fitness, target, generator, evolver, result;
geneStrategy = {
// The allowed character set (as an array)
characterSet: "ABCDEFGHIJKLMNOPQRSTUVWXYZ ".split(""),
/*
Pick a random character from the characterSet
*/
create: function getRandomGene() {
var randomNumber = Math.floor(Math.random() * this.characterSet.length);
return this.characterSet[randomNumber];
}
}; geneStrategy.mutate = geneStrategy.create; // Our mutation stragtegy is to simply get a random gene fitness = {
// The target (as an array of characters)
target: target.split(""),
equal: function (geneA, geneB) {
return (geneA === geneB ? 0 : 1);
},
sum: function (runningTotal, value) {
return runningTotal + value;
},
/*
We give one point to for each corect letter
*/
score: function (genes) {
var diff = genes.zip(this.target, this.equal); // create an array of ones and zeros
return diff.reduce(this.sum, 0); // Sum the array values together.
},
compare: function (scoreA, scoreB) {
return scoreA <= scoreB; // Lower scores are better
},
done: function (score) {
return score === 0; // We have matched the target string.
}
};
generator = new Generator(target.length, 0.05, geneStrategy); evolver = new Evolver(100, generator, fitness);
function showProgress(generation, fittest) {
document.write("Generation: " + generation + ", Best: " + fittest.individual.join("") + ", fitness:" + fittest.score + "
");
} result = evolver.run(showProgress);</lang> Output:
Generation: 0, Best: KSTFOKJC XZYLWCLLGYZJNXYEGHE, fitness:25 Generation: 10, Best: KOTFINJC XX LS LIGYZT WEPSHL, fitness:14 Generation: 20, Best: KBTHINKS BT LS LIGNZA WEPSEL, fitness:8 Generation: 30, Best: KETHINKS IT BS LISNZA WEASEL, fitness:5 Generation: 40, Best: KETHINKS IT IS LIKEZA WEASEL, fitness:2 Generation: 50, Best: METHINKS IT IS LIKEZA WEASEL, fitness:1 Generation: 52, Best: METHINKS IT IS LIKE A WEASEL, fitness:0
Julia
<lang julia>fitness(a::AbstractString, b::AbstractString) = count(l == t for (l, t) in zip(a, b)) function mutate(str::AbstractString, rate::Float64)
L = collect(Char, " ABCDEFGHIJKLMNOPQRSTUVWXYZ")
return map(str) do c
if rand() < rate rand(L) else c end
end
end
function evolve(parent::String, target::String, mutrate::Float64, nchild::Int)
println("Initial parent is $parent, its fitness is $(fitness(parent, target))")
gens = 0
while parent != target
children = collect(mutate(parent, mutrate) for i in 1:nchild)
bestfit, best = findmax(fitness.(children, target))
parent = children[best]
gens += 1
if gens % 10 == 0
println("After $gens generations, the new parent is $parent and its fitness is $(fitness(parent, target))")
end
end
println("After $gens generations, the parent evolved into the target $target")
end
evolve("IU RFSGJABGOLYWF XSMFXNIABKT", "METHINKS IT IS LIKE A WEASEL", 0.08998, 100)</lang>
- Output:
Initial parent is IU RFSGJABGOLYWF XSMFXNIABKT, its fitness is 1 After 10 generations, the new parent is MOTBSNGTABTTIL LIXEMA WMALSN and its fitness is 13 After 20 generations, the new parent is METHINGATITUIS LIXE A WEASEQ and its fitness is 22 After 30 generations, the new parent is METHINKSLIT ISELIAE A WEASES and its fitness is 24 After 40 generations, the new parent is METHINKS IT IS LINE A WEASEL and its fitness is 27 After 50 generations, the new parent is METHINKS IT IS LINE A WEASEL and its fitness is 27 After 60 generations, the new parent is METHINKS IT IS PIKE A WEASEL and its fitness is 27 After 70 generations, the new parent is METHINKS IT IS AIKE A WEASEL and its fitness is 27 After 80 generations, the new parent is METHINKS IT IS AIKE A WEASEL and its fitness is 27 After 81 generations, the parent evolved into the target METHINKS IT IS LIKE A WEASEL
Kotlin
<lang scala>import java.util.*
val target = "METHINKS IT IS LIKE A WEASEL" val validChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ "
val random = Random()
fun randomChar() = validChars[random.nextInt(validChars.length)] fun hammingDistance(s1: String, s2: String) =
s1.zip(s2).map { if (it.first == it.second) 0 else 1 }.sum()
fun fitness(s1: String) = target.length - hammingDistance(s1, target)
fun mutate(s1: String, mutationRate: Double) =
s1.map { if (random.nextDouble() > mutationRate) it else randomChar() }
.joinToString(separator = "")
fun main(args: Array<String>) {
val initialString = (0 until target.length).map { randomChar() }.joinToString(separator = "")
println(initialString) println(mutate(initialString, 0.2))
val mutationRate = 0.05 val childrenPerGen = 50
var i = 0
var currVal = initialString
while (currVal != target) {
i += 1
currVal = (0..childrenPerGen).map { mutate(currVal, mutationRate) }.maxBy { fitness(it) }!!
}
println("Evolution found target after $i generations")
}</lang>
Liberty BASIC
<lang lb>C = 10 'mutaterate has to be greater than 1 or it will not mutate mutaterate = 2 mutationstaken = 0 generations = 0 Dim parentcopies$((C - 1)) Global targetString$ : targetString$ = "METHINKS IT IS LIKE A WEASEL" Global allowableCharacters$ : allowableCharacters$ = " ABCDEFGHIJKLMNOPQRSTUVWXYZ" currentminFitness = Len(targetString$)
For i = 1 To Len(targetString$)
parent$ = parent$ + Mid$(allowableCharacters$, Int(Rnd(1) + 1 * Len(allowableCharacters$)), 1) 'corrected line
Next i
Print "Parent = " + parent$
While parent$ <> targetString$
generations = (generations + 1)
For i = 0 To (C - 1)
parentcopies$(i) = mutate$(parent$, mutaterate)
mutationstaken = (mutationstaken + 1)
Next i
For i = 0 To (C - 1)
currentFitness = Fitness(targetString$, parentcopies$(i))
If currentFitness = 0 Then
parent$ = parentcopies$(i)
Exit For
Else
If currentFitness < currentminFitness Then
currentminFitness = currentFitness
parent$ = parentcopies$(i)
End If
End If
Next i
CLS
Print "Generation - " + str$(generations)
Print "Parent - " + parent$
Scan
Wend
Print Print "Congratulations to me; I finished!" Print "Final Mutation: " + parent$ 'The ((i + 1) - (C)) reduces the total number of mutations that it took by one generation 'minus the perfect child mutation since any after that would not have been required. Print "Total Mutations Taken - " + str$(mutationstaken - ((i + 1) - (C))) Print "Total Generations Taken - " + str$(generations) Print "Child Number " + str$(i) + " has perfect similarities to your target." End
Function mutate$(mutate$, mutaterate)
If (Rnd(1) * mutaterate) > 1 Then
'The mutatingcharater randomizer needs 1 more than the length of the string
'otherwise it will likely take forever to get exactly that as a random number
mutatingcharacter = Int(Rnd(1) * (Len(targetString$) + 1))
mutate$ = Left$(mutate$, (mutatingcharacter - 1)) + Mid$(allowableCharacters$, Int(Rnd(1) * Len(allowableCharacters$)), 1) _
+ Mid$(mutate$, (mutatingcharacter + 1))
End If
End Function
Function Fitness(parent$, offspring$)
For i = 1 To Len(targetString$)
If Mid$(parent$, i, 1) <> Mid$(offspring$, i, 1) Then
Fitness = (Fitness + 1)
End If
Next i
End Function</lang>
Logo
<lang logo>make "target "|METHINKS IT IS LIKE A WEASEL|
to distance :w
output reduce "sum (map.se [ifelse equal? ?1 ?2 [0][1]] :w :target)
end
to random.letter
output pick "| ABCDEFGHIJKLMNOPQRSTUVWXYZ|
end
to mutate :parent :rate
output map [ifelse random 100 < :rate [random.letter] [?]] :parent
end
make "C 100 make "mutate.rate 10 ; percent
to breed :parent
make "parent.distance distance :parent
localmake "best.child :parent
repeat :C [
localmake "child mutate :parent :mutate.rate
localmake "child.distance distance :child
if greater? :parent.distance :child.distance [
make "parent.distance :child.distance
make "best.child :child
]
]
output :best.child
end
to progress
output (sentence :trials :parent "distance: :parent.distance)
end
to evolve
make "parent cascade count :target [lput random.letter ?] "|| make "trials 0 while [not equal? :parent :target] [ make "parent breed :parent print progress make "trials :trials + 1 ]
end</lang>
Lua
<lang lua>local target = "METHINKS IT IS LIKE A WEASEL" local alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ " local c, p = 100, 0.06
local function fitness(s) local score = #target for i = 1,#target do if s:sub(i,i) == target:sub(i,i) then score = score - 1 end end return score end
local function mutate(s, rate) local result, idx = "" for i = 1,#s do if math.random() < rate then idx = math.random(#alphabet) result = result .. alphabet:sub(idx,idx) else result = result .. s:sub(i,i) end end return result, fitness(result) end
local function randomString(len) local result, idx = "" for i = 1,len do idx = math.random(#alphabet) result = result .. alphabet:sub(idx,idx) end return result end
local function printStep(step, s, fit) print(string.format("%04d: ", step) .. s .. " [" .. fit .."]") end
math.randomseed(os.time()) local parent = randomString(#target) printStep(0, parent, fitness(parent))
local step = 0 while parent ~= target do local bestFitness, bestChild, child, fitness = #target + 1 for i = 1,c do child, fitness = mutate(parent, p) if fitness < bestFitness then bestFitness, bestChild = fitness, child end end parent, step = bestChild, step + 1 printStep(step, parent, bestFitness) end</lang>
M2000 Interpreter
Version 1
<lang M2000 Interpreter> Module WeaselAlgorithm {
Print "Evolutionary Algorithm"
\\ Weasel Algorithm
\\ Using dynamic array, which expand if no fitness change,
\\ and reduce to minimum when fitness changed
\\ Abandon strings when fitness change
\\ Also lambda function Mutate$ change when topscore=10, to change only one character
l$="ABCDEFGHIJKLMNOPQRSTUVWXYZ "
randomstring$=lambda$ l$ ->{
res$=""
For i=1 to 28: res$+=Mid$(L$,Random(1,27),1):next i
=res$
}
m$="METHINKS IT IS LIKE A WEASEL"
lm=len(m$)
fitness=lambda m$, lm (this$)-> {
score=0 : For i=1 to lm {score+=If(mid$(m$,i,1)=mid$(this$, i, 1)->1,0)} : =score
}
Mutate$=lambda$ l$ (w$)-> {
a=random(1,28) : insert a, 1 w$=mid$(l$, random(1,27),1)
If random(3)=1 Then b=a:while b=a {b=random(1,28)} : insert b, 1 w$=mid$(l$, random(1,27),1)
=w$
}
Mutate1$=lambda$ l$ (w$)-> {
insert random(1,28), 1 w$=mid$(l$, random(1,27),1) : =w$
}
f$=randomstring$()
topscore=0
last=0
Pen 11 {Print "Fitness |Target:", @(16),m$, @(47),"|Total Strings"}
Print Over $(3,8), str$(topscore/28,"##0.0%"),"",$(0),f$, 0
count=0
gen=30
mut=0
{
last=0
Dim a$(1 to gen)<<mutate$(f$)
mut+=gen
oldscore=topscore
For i=1 to gen {
topscore=max.data(topscore, fitness(a$(i)))
If oldscore<topscore Then last=i:Exit
}
If last>0 Then {
f$=a$(last) : gen=30 : If topscore=10 Then mutate$=mutate1$
} Else gen+=50
Print Over $(3,8), str$(topscore/28,"##0.0%"), "",$(0),f$, mut : refresh
count+=min(gen,i)
If topscore<28 Then loop
}
Print
Print "Results"
Print "I found this:"; a$(i)
Print "Total strings which evalute fitness:"; count
Print "Done"
} WeaselAlgorithm
</lang>
- Output:
Fitness |Target: METHINKS IT IS LIKE A WEASEL |Total strings
3,6% ZZBZSVEOWPSQGJXNIXTFQCDQTJFE 30
7,1% ZZBZSVEOWPSQGJXNIXTFQCDQAJFE 60
14,3% ZZBZSVEOWPTQGJXNIXTFACDQAJFE 90
17,9% ZZBZSVEOWPTQGJXNIXTFA DQAJFE 200
21,4% ZEBZSVEOWPTQGJXNIXTFA DQAJFE 230
25,0% ZEBZSVEOWPTQGJXNIXT A DQAJFE 260
28,6% MEBZSVEOCPTQGJXNIXT A DQAJFE 290
32,1% MEBZSVEOCITQGJXNIXT A DQAJFE 320
35,7% MEBZSVEOCITQGJXNIKT A DQAJFE 350
39,3% MEBZSVEOCITQGJ NIKT A DQAJFE 380
42,9% MEBZSVEOCITQGJ NIKT A WQAJFE 410
46,4% MEBZSVESCITQGJ NIKT A WQAJFE 440
50,0% MEBZSVESCITQIJ NIKT A WQAJFE 680
53,6% MEBZSVESCIT IJ NIKT A WQAJFE 1100
57,1% MEBZSVESCIT IJ LIKT A WQAJFE 1130
60,7% MEBZSVKSCIT IJ LIKT A WQAJFE 1240
64,3% MEBZSVKS IT IJ LIKT A WQAJFE 1480
67,9% MEBZSNKS IT IJ LIKT A WQAJFE 1900
71,4% MEBHSNKS IT IJ LIKT A WQAJFE 2010
75,0% METHSNKS IT IJ LIKT A WQAJFE 2430
78,6% METHSNKS IT IJ LIKE A WQAJFE 2670
82,1% METHSNKS IT IJ LIKE A WQAJFL 3090
85,7% METHSNKS IT IJ LIKE A WEAJFL 3330
89,3% METHSNKS IT IJ LIKE A WEASFL 3980
92,9% METHINKS IT IJ LIKE A WEASFL 4400
96,4% METHINKS IT IJ LIKE A WEASEL 5050
100,0% METHINKS IT IS LIKE A WEASEL 5290
Results
I found this:METHINKS IT IS LIKE A WEASEL
Total strings which evaluate fitness:3230
Version 2
The second version check fitness for all strings until became 28 (100%)
Also here we have one Mutate function which change letters using 5% probability for each place in the parent string.
<lang M2000 Interpreter> Module WeaselAlgorithm2 {
Print "Evolutionary Algorithm"
\\ Weasel Algorithm
\\ Using dynamic array, which expand if no fitness change,
\\ and reduce to minimum when fitness changed
l$="ABCDEFGHIJKLMNOPQRSTUVWXYZ "
randomstring$=lambda$ l$ ->{
res$=""
For i=1 to 28: res$+=Mid$(L$,Random(1,27),1):next i
=res$
}
m$="METHINKS IT IS LIKE A WEASEL"
lm=len(m$)
fitness=lambda m$, lm (this$)-> {
score=0 : For i=1 to lm {score+=If(mid$(m$,i,1)=mid$(this$, i, 1)->1,0)} : =score
}
Mutate$=lambda$ l$ (w$)-> {
for i=1 to len(w$) {
if random(1,100)<=5 then { insert i, 1 w$=mid$(l$, random(1,27),1) }
}
=w$
}
f$=randomstring$()
topscore=0
last=0
Pen 11 {Print "Fitness |Target:", @(16),m$, @(47),"|Total Strings"}
Print Over $(3,8), str$(topscore/28,"##0.0%"),"",$(0),f$, 0
count=0
gen=30
mut=0
{
last=0
Dim a$(1 to gen)<<mutate$(f$)
mut+=gen
oldscore=topscore
For i=1 to gen {
topscore=max.data(topscore, fitness(a$(i)))
If oldscore<topscore Then last=i: oldscore=topscore
}
If last>0 Then {
f$=a$(last) : gen=30
} Else gen+=50
Print Over $(3,8), str$(topscore/28,"##0.0%"), "",$(0),f$, mut : refresh
count+=min(gen,i)
If topscore<28 Then loop
}
Print
Print "Results"
Print "I found this:"; a$(last)
Print "Total strings which evalute fitness:"; count
Print "Done"
} WeaselAlgorithm2 </lang>
m4
This is written in POSIX m4, but seems to run least annoyingly in GNU m4. (For instance, OpenBSD m4 may resist attempts to use the interrupt key.)
You may, like I, lose patience waiting for it to get that last character. But I have tested that the program terminates, by running it with a one-character target. :)
Note that it writes to a file called ‘__random_number__’. The random number generator here is the best I have come up with that works in all the m4 implementations I have installed. (Something using sysval did not work in OpenBSD m4.)
This is not the best use of m4, and I am far from an m4 guru, but it seemed unlikely anyone else was going to write an m4 example for this task. The better my m4 skills, the better I am going to be at everything that can be preprocessed, and at GNU Autotools (which, unlike many, I like a lot). So I wrote this.
<lang m4>divert(-1)
- Get a random number from 0 to one less than $1.
- (Note that this is not a very good RNG. Also it writes a file.)
- Usage: randnum(N) (Produces a random integer in 0..N-1)
define(`randnum',
`syscmd(`echo $RANDOM > __random_number__')eval(include(__random_number__) % ( $1 ))')
- The *target* specified in the Rosetta Code task.
define(`target',`METHINKS IT IS LIKE A WEASEL')
define(`alphabet',`ABCDEFGHIJKLMNOPQRSTUVWXYZ ') define(`random_letter',`substr(alphabet,randnum(len(alphabet)),1)')
define(`create_primogenitor',`_$0(`')') define(`_create_primogenitor',`ifelse(len(`$1'),len(target),`$1',
`$0(`$1'random_letter)')')
- The *parent* specified in the Rosetta Code task.
define(`parent',`'create_primogenitor)
- Usage: mutate_letter(STRING,INDEX)
define(`mutate_letter',
`substr(`$1',0,`$2')`'random_letter`'substr(`$1',incr(`$2'))')
- Usage: mutate_letter_at_rate(STRING,INDEX,MUTATION_RATE)
define(`mutate_letter_at_rate',
`ifelse(eval(randnum(100) < ($3)),1,`mutate_letter(`$1',`$2')',`$1')')
- The *mutate* procedure specified in the Rosetta Code task. The
- mutation rate is given in percents.
- Usage: mutate(STRING,MUTATION_RATE)
define(`mutate',`_$0(`$1',`$2',len(`$1'))') define(`_mutate',
`ifelse($3,0,`$1',
`$0(mutate_letter_at_rate(`$1',decr($3),`$2'),`$2',decr($3))')')
- The *fitness* procedure specified in the Rosetta Code
- task. "Fitness" here is simply how many letters match.
- Usage: fitness(STRING)
define(`fitness',`_$0(`$1',target,0)') define(`_fitness',
`ifelse(`$1',`',$3,
`ifelse(`'substr(`$1',0,1),`'substr(`$2',0,1),
`$0(`'substr(`$1',1),`'substr(`$2',1),incr($3))',
`$0(`'substr(`$1',1),`'substr(`$2',1),$3)')')')
- Usage: have_child(PARENT,MUTATION_RATE)
- The result is either the parent or the child: whichever has the
- greater fitness. If they are equally fit, one is chosen arbitrarily.
- (Note that, in the current implementation, fitnesses are not
- memoized.)
define(`have_child', `pushdef(`_child_',mutate(`$1',`$2'))`'dnl ifelse(eval(fitness(`'_child_) < fitness(`$1')),1,`$1',`_child_')`'dnl popdef(`_child_')')
- Usage: next_parent(PARENT,NUM_CHILDREN,MUTATION_RATE)
- Note that a string is discarded as soon as it is known it will not
- be in the next generation. If some strings have the same highest
- fitness, one of them is chosen arbitrarily.
define(`next_parent',
`ifelse(`$2',0,`$1',
`$0(`'have_child(`$1',`$3'),decr(`$2'),`$3')')')
define(`repeat_until_equal',
`ifelse(`$1',`'target,`[$1]',
`pushdef(`_the_horta_',`'next_parent(`$1',`$2',`$3'))`'dnl [_the_horta_] $0(`'_the_horta_,`$2',`$3')`'dnl popdef(`_the_horta_')')')
divert`'dnl [parent] repeat_until_equal(parent,10,10)</lang>
- Output:
$ m4 evolutionary_algorithm.m4 [NETE PWTKFNDAJRAGRDXGOCKNMQU] [NETEEPWTUFPYMBLAGRVMYOCKJBQU] [PETEWPWFGFTYACLHGRVTPFUMKBSS] [METEFYGUUHQRGCDHGLVTBPFIKUSS] [TETSFIESUHVDGCDNQOZ CPFHKUAC] [YETOMIESEHVYLWXWQCZAGHOJS AL] [UETOZYESKAVUUWXYQPDBYHPYGAAL] [JETJCZ SDLVUSDHYOPCTTEOYZAAL] [CETSPZGS LPUSDHYGPCTUEOIQW L] [BETBLZUS LEKSDQYGWCWUAOEAW L] [XETBCXUSPLF DQZLWLUUAOEAX L] [XETXCXESPLB DEZLWZUSAOEAX L] [CETTKXQSHLE OCLLPUUTAOEAX L] [CETTUGQSHLE OCLAPUUTAOEAX L] [CETTEGISHLW O LAPUUTSJEAX X] [CETTAGHSBFW MO LACUNKSBEAXPX] [CETTAGHSBFW MO LACUNKSBEAXPX] [CETLFJHSBFC NM LACLMOSBEAXPY] [QETVFEPSBFD NY LFXKMOFOEAXWG] [NETVYEPSBFI HL LFXKMOQOEAXWD] [NETVJEPSWDI HL LFXKMOQOEAVWX] [NETVJEPSWDI HY LFXKMOQOEAVWX] [NETVJEPSWDI JY LFXKMOQOEAVWX] [NETVJEPSMDI JD LCKKMOFJELBWX] [NETYJEPSIDI JD LNKKMOIUEDPWX] [NPTYRMASIYZ ED LSKETOISEDPXP] [NPTYRJESIY WV LZKE OISEDPXP] [SNTYZJSSIVH WV LCKE HQSEDPIP] [XNTYZJSSJVH WE LCKE HQSEDUYP] [XNTYZJSSJVH WE LTKE HQKEDCYP] [XNTFOSPSOPH WE LTKE HQKEKCVS] [XCTGOSPSOPH WE LTKE TGKEKCVJ] [XCTGOSPSGDH WT LGKE KGWEBCVJ] [ATTGEYPSKDH WT LRKE YDWESCVJ] [ATTOE PSKDS WTSL KE ADWESCVJ] [EUTOOLPSKDF WTSL KE AMWELCDJ] [EITOOLPSKDS JTSL KE ATWEVJDJ] [EITOOLPSGDE ZTSL KE ASWEWJDY] [EJTXOLLSGDE Z PL KE ALWEWJDY] [EJTXOPLSGZE C SL KE ALWEWGDY] [EHTIOPLSGZE DBFL KE ALWEWNDY] [EEWLHZLSGCJBKBFL KE A WEWRZV] [EEWLBZLSPLJZKIFL KE A WE R U] [ZEWDBZLSPRJZKIFL KE C WEAQ U] [BEWDNBLSPRKZNIYLCKE M WEAQ U] [DEWDNBLSPRKRNAYLCKE M WEAQ U] [DEWDCBLSPRKRNRYLCKE Y WEAQVU] [DEWDLUISPRZRERYLCKE Y WEALEU] [DECDLUISHRZREHPLCKE Y WEALEK] ^C $
Mathematica / Wolfram Language
<lang Mathematica>target = "METHINKS IT IS LIKE A WEASEL"; alphabet = Append[CharacterRange["A", "Z"], " "]; fitness = HammingDistance[target, #] &; mutate[str_String, rate_ : 0.01] := StringReplace[
str, _ /; RandomReal[] < rate :> RandomChoice[alphabet]
]
mutationRate = 0.02; c = 100; NestWhileList[
First@MinimalBy[
Thread[mutate[ConstantArray[#, c], mutationRate]],
fitness
] &,
mutate[target, 1],
fitness@# > 0 &
] // ListAnimate</lang>
MATLAB
This solution implements a class called EvolutionaryAlgorithm, the members of the class are the variables required by the task description. You can see them using the disp() function on an instance of the class. To use this class you only need to specify the target, mutation rate, number of children (called C in the task spec), and maximum number of evolutionary cycles. After doing so, call the evolve() function on the class instance to start the evolution cycle. Note, the fitness function computes the hamming distance between the target string and another string, this can be changed if a better heuristic exists.
To use this code, create a folder in your MATLAB directory titled "@EvolutionaryAlgorithm". Within that folder save this code in a file named "EvolutionaryAlgorithm.m".
<lang MATLAB>%This class impliments a string that mutates to a target classdef EvolutionaryAlgorithm
properties
target;
parent;
children = {};
validAlphabet;
%Constants
numChildrenPerIteration;
maxIterations;
mutationRate;
end
methods
%Class constructor
function family = EvolutionaryAlgorithm(target,mutationRate,numChildren,maxIterations)
family.validAlphabet = char([32 (65:90)]); %Space char and A-Z
family.target = target;
family.children = cell(numChildren,1);
family.numChildrenPerIteration = numChildren;
family.maxIterations = maxIterations;
family.mutationRate = mutationRate;
initialize(family);
end %class constructor
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Helper functions and class get/set functions
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%setAlphabet() - sets the valid alphabet for the current instance
%of the EvolutionaryAlgorithm class.
function setAlphabet(family,alphabet)
if(ischar(alphabet))
family.validAlphabet = alphabet;
%Makes change permanent
assignin('caller',inputname(1),family);
else
error 'New alphabet must be a string or character array';
end
end
%setTarget() - sets the target for the current instance
%of the EvolutionaryAlgorithm class.
function setTarget(family,target)
if(ischar(target))
family.target = target;
%Makes change permanent
assignin('caller',inputname(1),family);
else
error 'New target must be a string or character array';
end
end
%setMutationRate() - sets the mutation rate for the current instance
%of the EvolutionaryAlgorithm class.
function setMutationRate(family,mutationRate)
if(isnumeric(mutationRate))
family.mutationRate = mutationRate;
%Makes change permanent
assignin('caller',inputname(1),family);
else
error 'New mutation rate must be a double precision number';
end
end
%setMaxIterations() - sets the maximum number of iterations during
%evolution for the current instance of the EvolutionaryAlgorithm class.
function setMaxIterations(family,maxIterations)
if(isnumeric(maxIterations))
family.maxIterations = maxIterations;
%Makes change permanent
assignin('caller',inputname(1),family);
else
error 'New maximum amount of iterations must be a double precision number';
end
end
%display() - overrides the built-in MATLAB display() function, to
%display the important class variables
function display(family)
disp([sprintf('Target: %s\n',family.target)...
sprintf('Parent: %s\n',family.parent)...
sprintf('Valid Alphabet: %s\n',family.validAlphabet)...
sprintf('Number of Children: %d\n',family.numChildrenPerIteration)...
sprintf('Mutation Rate [0,1]: %d\n',family.mutationRate)...
sprintf('Maximum Iterations: %d\n',family.maxIterations)]);
end
%disp() - overrides the built-in MATLAB disp() function, to
%display the important class variables
function disp(family)
display(family);
end
%randAlphabetElement() - Generates a random character from the
%valid alphabet for the current instance of the class.
function elements = randAlphabetElements(family,numChars)
%Sample the valid alphabet randomly from the uniform
%distribution
N = length(family.validAlphabet);
choices = ceil(N*rand(1,numChars));
elements = family.validAlphabet(choices);
end
%initialize() - Sets the parent to a random string of length equal
%to the length of the target
function parent = initialize(family)
family.parent = randAlphabetElements(family,length(family.target));
parent = family.parent;
%Makes changes to the instance of EvolutionaryAlgorithm permanent
assignin('caller',inputname(1),family);
end %initialize
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Functions required by task specification
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%mutate() - generates children from the parent and mutates them
function mutate(family)
sizeParent = length(family.parent);
%Generate mutatant children sequentially
for child = (1:family.numChildrenPerIteration)
parentCopy = family.parent;
for charIndex = (1:sizeParent)
if (rand(1) < family.mutationRate)
parentCopy(charIndex) = randAlphabetElements(family,1);
end
end
family.children{child} = parentCopy;
end
%Makes changes to the instance of EvolutionaryAlgorithm permanent
assignin('caller',inputname(1),family);
end %mutate
%fitness() - Computes the Hamming distance between the target
%string and the string input as the familyMember argument
function theFitness = fitness(family,familyMember)
if not(ischar(familyMember))
error 'The second argument must be a string';
end
theFitness = sum(family.target == familyMember);
end
%evolve() - evolves the family until the target is reached or it
%exceeds the maximum amount of iterations
function [iteration,mostFitFitness] = evolve(family)
iteration = 0;
mostFitFitness = 0;
targetFitness = fitness(family,family.target);
disp(['Target fitness is ' num2str(targetFitness)]);
while (mostFitFitness < targetFitness) && (iteration < family.maxIterations)
iteration = iteration + 1;
mutate(family);
parentFitness = fitness(family,family.parent);
mostFit = family.parent;
mostFitFitness = parentFitness;
for child = (1:family.numChildrenPerIteration)
childFitness = fitness(family,family.children{child});
if childFitness > mostFitFitness
mostFit = family.children{child};
mostFitFitness = childFitness;
end
end
family.parent = mostFit;
disp([num2str(iteration) ': ' mostFit ' - Fitness: ' num2str(mostFitFitness)]);
end
%Makes changes to the instance of EvolutionaryAlgorithm permanent
assignin('caller',inputname(1),family);
end %evolve
end %methods
end %classdef</lang> Sample Output: (Some evolutionary cycles omitted for brevity) <lang MATLAB>>> instance = EvolutionaryAlgorithm('METHINKS IT IS LIKE A WEASEL',.08,50,1000) Target: METHINKS IT IS LIKE A WEASEL Parent: UVEOCXXFBGDCSFNMJQNWTPJ PCVA Valid Alphabet: ABCDEFGHIJKLMNOPQRSTUVWXYZ Number of Children: 50 Mutation Rate [0,1]: 8.000000e-002 Maximum Iterations: 1000
>> evolve(instance); Target fitness is 28 1: MVEOCXXFBYD SFCMJQNWTPM PCVA - Fitness: 2 2: MEEOCXXFBYD SFCMJQNWTPM PCVA - Fitness: 3 3: MEEHCXXFBYD SFCMJXNWTPM ECVA - Fitness: 4 4: MEEHCXXFBYD SFCMJXNWTPM ECVA - Fitness: 4 5: METHCXAFBYD SFCMJXNWXPMARPVA - Fitness: 5 6: METHCXAFBYDFSFCMJXNWX MARSVA - Fitness: 6 7: METHCXKFBYDFBFCQJXNWX MATSVA - Fitness: 7 8: METHCXKFBYDFBF QJXNWX MATSVA - Fitness: 8 9: METHCXKFBYDFBF QJXNWX MATSVA - Fitness: 8 10: METHCXKFUYDFBF QJXNWX MITSEA - Fitness: 9 20: METHIXKF YTBOF LIKN G MIOSEI - Fitness: 16 30: METHIXKS YTCOF LIKN A MIOSEL - Fitness: 19 40: METHIXKS YTCIF LIKN A MEUSEL - Fitness: 21 50: METHIXKS YT IS LIKE A PEUSEL - Fitness: 24 100: METHIXKS YT IS LIKE A WEASEL - Fitness: 26 150: METHINKS YT IS LIKE A WEASEL - Fitness: 27 195: METHINKS IT IS LIKE A WEASEL - Fitness: 28</lang>
Genetic Algorithm Example
This solution uses a subset of evolutionary programming called the Genetic Algorithm. It is very similar to the basic evolutionary algorithm, but instead of just using mutations it also makes use of other genetic operators. The algorithm begins by importing the target text (in this case 'METHINKS IT IS LIKE A WEASEL') and then the algorithm performs genetic operations until the target string is obtained or the maximum number of iterations is reached (which will never happen with the given target string). The algorithm first measures how fit each potential answer is, and then selects strings to perform operations on. The selected answers go through the crossover stage where their data is split and recombined into new potential answers. Then a chance for the answer to mutate slightly occurs and the algorithm repeats itself.
Presented is very efficient and vectorized version of the genetic algorithm. To run the algorithm simply copy and paste the code into a script and hit run. You can adjust the style of selection and crossover used to learn more about how they effect solutions. The algorithm can also handle any target string that uses ASCII characters and will allow for any phrase to be used regardless of length. <lang MATLAB> %% Genetic Algorithm -- Solves For A User Input String
% #### PLEASE NOTE: you can change the selection and crossover type in the % parameters and see how the algorithm changes. ####
clear;close all;clc; %Clears variables, closes windows, and clears the command window tic % Begins the timer
%% Select Target String target = 'METHINKS IT IS LIKE A WEASEL'; % *Can Be Any String With Any Values and Any Length!* % but for this example we use 'METHINKS IT IS LIKE A WEASEL'
%% Parameters popSize = 1000; % Population Size (100-10000 generally produce good results) genome = length(target); % Genome Size mutRate = .01; % Mutation Rate (5%-25% produce good results) S = 4; % Tournament Size (2-6 produce good results) best = Inf; % Initialize Best (arbitrarily large) MaxVal = max(double(target)); % Max Integer Value Needed ideal = double(target); % Convert Target to Integers
selection = 0; % 0: Tournament
% 1: 50% Truncation
crossover = 1; % 0: Uniform crossover
% 1: 1 point crossover
% 2: 2 point crossover
%% Initialize Population Pop = round(rand(popSize,genome)*(MaxVal-1)+1); % Creates Population With Corrected Genome Length
for Gen = 1:1e6 % A Very Large Number Was Chosen, But Shouldn't Be Needed
%% Fitness
% The fitness function starts by converting the characters into integers and then
% subtracting each element of each member of the population from each element of
% the target string. The function then takes the absolute value of
% the differences and sums each row and stores the function as a mx1 matrix.
F = sum(abs(bsxfun(@minus,Pop,ideal)),2);
% Finding Best Members for Score Keeping and Printing Reasons
[current,currentGenome] = min(F); % current is the minimum value of the fitness array F
% currentGenome is the index of that value in the F array
% Stores New Best Values and Prints New Best Scores
if current < best
best = current;
bestGenome = Pop(currentGenome,:); % Uses that index to find best value
fprintf('Gen: %d | Fitness: %d | ',Gen, best); % Formatted printing of generation and fitness
disp(char(bestGenome)); % Best genome so far
elseif best == 0
break % Stops program when we are done
end
%% Selection % TOURNAMENT if selection == 0 T = round(rand(2*popSize,S)*(popSize-1)+1); % Tournaments [~,idx] = min(F(T),[],2); % Index to Determine Winners W = T(sub2ind(size(T),(1:2*popSize)',idx)); % Winners % 50% TRUNCATION elseif selection == 1 [~,V] = sort(F,'descend'); % Sort Fitness in Ascending Order V = V(popSize/2+1:end); % Winner Pool W = V(round(rand(2*popSize,1)*(popSize/2-1)+1))'; % Winners end %% Crossover % UNIFORM CROSSOVER if crossover == 0 idx = logical(round(rand(size(Pop)))); % Index of Genome from Winner 2 Pop2 = Pop(W(1:2:end),:); % Set Pop2 = Pop Winners 1 P2A = Pop(W(2:2:end),:); % Assemble Pop2 Winners 2 Pop2(idx) = P2A(idx); % Combine Winners 1 and 2 % 1-POINT CROSSOVER elseif crossover == 1 Pop2 = Pop(W(1:2:end),:); % New Population From Pop 1 Winners P2A = Pop(W(2:2:end),:); % Assemble the New Population Ref = ones(popSize,1)*(1:genome); % The Reference Matrix idx = (round(rand(popSize,1)*(genome-1)+1)*ones(1,genome))>Ref; % Logical Indexing Pop2(idx) = P2A(idx); % Recombine Both Parts of Winners % 2-POINT CROSSOVER elseif crossover == 2 Pop2 = Pop(W(1:2:end),:); % New Pop is Winners of old Pop P2A = Pop(W(2:2:end),:); % Assemble Pop2 Winners 2 Ref = ones(popSize,1)*(1:genome); % Ones Matrix CP = sort(round(rand(popSize,2)*(genome-1)+1),2); % Crossover Points idx = CP(:,1)*ones(1,genome)<Ref&CP(:,2)*ones(1,genome)>Ref; % Index Pop2(idx)=P2A(idx); % Recombine Winners end %% Mutation idx = rand(size(Pop2))<mutRate; % Index of Mutations Pop2(idx) = round(rand([1,sum(sum(idx))])*(MaxVal-1)+1); % Mutated Value %% Reset Poplulations Pop = Pop2;
end
toc % Ends timer and prints elapsed time </lang>
Sample Output: (The Algorithm was run with 1000 population members, Tournament Selection (with tournament size of 4), 1-Point Crossover, and a mutation rate of 10%). <lang MATLAB> Gen: 1 | Fitness: 465 | C�I1%G+<%?R�8>9�JU#(E�UO�PHI Gen: 2 | Fitness: 429 | W=P6>D�I)VU6$T 99,� B�BMP0JH Gen: 3 | Fitness: 366 | P�;R08AS�GJ�IS&T38IE�)SJERLJ Gen: 4 | Fitness: 322 | KI8M5LAS�GJ�IS�SP�@)D�V@ JCP Gen: 5 | Fitness: 295 | UAUR08AS�GJ�IS�8HG*�+�=C?UB( Gen: 6 | Fitness: 259 | VCUQH35S�HR4.L�ISJQ%J�OC*T=E Gen: 7 | Fitness: 226 | LFB8GPET(LODKQ�KQ<K E*PEMA6I Gen: 8 | Fitness: 192 | EPKOLCIR�QQ�NF�QG:B(D/U>BQGF Gen: 9 | Fitness: 159 | N8R7?SOU�NO$OK O?K?!;�MB?QHG Gen: 10 | Fitness: 146 | TGN@EQR4)PS%IS#TFJQ%A!U>BVLI Gen: 11 | Fitness: 120 | L?VMALJS%?R EK IILE�6'RRERLJ Gen: 12 | Fitness: 102 | R@T9COMR�NU CS*R?K?!; VD>LCL Gen: 13 | Fitness: 96 | NENMVOMR�NU CS*R?K?!; VD>LCL Gen: 14 | Fitness: 82 | REJGNPMU�KR CS JKI@+D�UD?QHG Gen: 15 | Fitness: 75 | NETI=HPQ�FT ID EFKE D"WD>QDQ Gen: 16 | Fitness: 70 | R@TKCOOT)@R$IS KKLE�D"WC?UBJ Gen: 17 | Fitness: 61 | NESIKQRP�NU CS�MFKE ; SEETCP Gen: 18 | Fitness: 57 | LFSGLPTN�NU GQ IIKE D"VD>LCL Gen: 19 | Fitness: 40 | NENKJLMS�GS%IS#MFKE B UFATCL Gen: 21 | Fitness: 39 | NETIGPEU�KR IS IIKD"? UFDQEK Gen: 22 | Fitness: 33 | NETGCOMT�LU IS#MFKE B UFATCL Gen: 23 | Fitness: 32 | NETIKNPQ�NU IS#IIKE B UFATCL Gen: 24 | Fitness: 27 | NETKJLMS�LU IS MFKE B UFATCL Gen: 25 | Fitness: 23 | LETIKOMS LU IS IIKE D WEDQEK Gen: 26 | Fitness: 22 | NETIKMJS LU IS IIKE D WEDQEK Gen: 27 | Fitness: 20 | LETIKOMS LU IS KILE B"WFATCL Gen: 28 | Fitness: 19 | NESGJQJS�GU IS KIKE B WFATEK Gen: 29 | Fitness: 16 | NETIHPMS KR IS KIKE B WFATEK Gen: 30 | Fitness: 15 | NESHLPKS KU IS KIKE B WFATEK Gen: 31 | Fitness: 13 | NETGGNKS KU IS KIKE C WFATEK Gen: 32 | Fitness: 12 | NETHGNJS IU IS JIKE B WFATCL Gen: 33 | Fitness: 11 | NETIJPKS IU IS KIKE B WFATEK Gen: 35 | Fitness: 8 | LEUIHNJS IT IS JIKE A WEATEL Gen: 37 | Fitness: 7 | NETIHNJS IS IS LIKE B WFASEL Gen: 38 | Fitness: 6 | NETHGNJS IT IS LIKE A WFASEK Gen: 39 | Fitness: 4 | METGHNKS IT IS LIKE B WEATEL Gen: 42 | Fitness: 3 | NETHINKS IT IS KIKE B WEASEL Gen: 43 | Fitness: 2 | NETHINKS IT IS LIKE A WFASEL Gen: 44 | Fitness: 1 | METHHNKS IT IS LIKE A WEASEL Gen: 46 | Fitness: 0 | METHINKS IT IS LIKE A WEASEL Elapsed time is 0.099618 seconds. </lang>
Nanoquery
<lang Nanoquery>import Nanoquery.Util
target = "METHINKS IT IS LIKE A WEASEL" tbl = "ABCDEFGHIJKLMNOPQRSTUVWXYZ " copies = 30 chance = 0.09 rand = new(Random)
// returns a random string of the specified length def rand_string(length) global tbl global rand
ret = ""
for i in range(1, length) ret += tbl[rand.getInt(len(tbl))] end
return ret end
// gets the fitness of a given string def fitness(string) global target fit = 0
for i in range(0, len(string) - 1) if string[i] != target[i] fit -= 1 end end
return fit end
// mutates the specified string with a chance of 0.09 by default def mutate(string) global chance global rand global tbl mutated = string
for i in range(0, len(mutated) - 1) if rand.getFloat() <= chance mutated[i] = tbl[rand.getInt(len(tbl))] end end
return mutated end
// a function to find the index of the string with the best fitness def most_fit(strlist) global target
best_score = -(len(target) + 1) best_index = 0
for j in range(0, len(strlist) - 1) fit = fitness(strlist[j]) if fit > best_score best_index = j best_score = fit end end
return {best_index, best_score} end
parent = rand_string(len(target)); iter = 1 while parent != target children = {}
for i in range(1, 30) children.append(mutate(parent)) end
fit = most_fit(children) parent = children[fit[0]] print format("iter %d, score %d: %s\n", iter, fit[1], parent)
iter += 1 end</lang>
- Output:
iter 1, score -26: QVAZCNKALPVKLYYNCECRURIRLASN iter 2, score -25: QVAZ NKALPVKLYYNIECRURIRLASN iter 3, score -24: QVAZINKALPVKLYYNIRCRURIRLASN iter 4, score -24: QVAZINKAYPVKLYYNIRCRURISLASN iter 5, score -23: QVAZINKAYPTKLYYNIRCPURISLASN iter 6, score -21: QAAHINKAYPTKLYYNIRCPARISLASN iter 7, score -20: QATHINKAZPTKLHYNIWCPARISLASN iter 8, score -19: QETHINKAZKTKEHYVIWIPARISLASB iter 9, score -19: PETHINKAZKTKUHYVIWIPARISLASB iter 10, score -18: PETHINKSZKTKUHYVIWIPARIBIASB ... iter 202, score -1: METHINKS IT IS LIKE A WEESEL iter 203, score -1: METHINKS IT IS LIKE A WEESEL iter 204, score -1: METHINKS IT IS LIKE A WEESEL iter 205, score -1: METHINKS IT IS LIKE A WEESEL iter 206, score -1: METHINKS IT IS LIKE A WEESEL iter 207, score 0: METHINKS IT IS LIKE A WEASEL
Nim
<lang nim>import random
const
Target = "METHINKS IT IS LIKE A WEASEL" Alphabet = " ABCDEFGHIJLKLMNOPQRSTUVWXYZ" P = 0.05 C = 100
proc negFitness(trial: string): int =
for i in 0 .. trial.high:
if Target[i] != trial[i]:
inc result
proc mutate(parent: string): string =
for c in parent: result.add (if rand(1.0) < P: sample(Alphabet) else: c)
randomize()
var parent = "" for _ in 1..Target.len:
parent.add sample(Alphabet)
var i = 0 while parent != Target:
var copies = newSeq[string](C) for i in 0 .. copies.high: copies[i] = parent.mutate()
var best = copies[0]
for i in 1 .. copies.high:
if negFitness(copies[i]) < negFitness(best):
best = copies[i]
parent = best
echo i, " ", parent inc i</lang>
- Output:
0 DDTAXEPAFNI RIKNLUBKPXKBFHGA 1 DDTJXEPAFNI RIKNLUB PXKBFHGA 2 CDTJXEPAFNI RI NLUB ZXKBFHGA 3 CDTJXEPAFNI RI KLUB ZXKEFHGA [...] 37 METJINKS IT IS LIBE A WEANEL [...] 70 MET INKS IT IS LIKE A WEASEL 71 METHINKS IT IS LIKE A WEASEL
Objeck
<lang objeck>bundle Default {
class Evolutionary {
target : static : String;
possibilities : static : Char[];
C : static : Int;
minMutateRate : static : Float;
perfectFitness : static : Int;
parent : static : String ;
rand : static : Float;
function : Init() ~ Nil {
target := "METHINKS IT IS LIKE A WEASEL";
possibilities := "ABCDEFGHIJKLMNOPQRSTUVWXYZ "->ToCharArray();
C := 100;
minMutateRate := 0.09;
perfectFitness := target->Size();
}
function : fitness(trial : String) ~ Int {
retVal := 0;
each(i : trial) {
if(trial->Get(i) = target->Get(i)) {
retVal += 1;
};
};
return retVal;
}
function : newMutateRate() ~ Float {
x : Float := perfectFitness - fitness(parent);
y : Float := perfectFitness->As(Float) * (1.01 - minMutateRate);
return x / y;
}
function : mutate(parent : String, rate : Float) ~ String {
retVal := "";
each(i : parent) {
rand := Float->Random();
if(rand <= rate) {
rand *= 1000.0;
intRand := rand->As(Int);
index : Int := intRand % possibilities->Size();
retVal->Append(possibilities[index]);
}
else {
retVal->Append(parent->Get(i));
};
};
return retVal;
}
function : Main(args : String[]) ~ Nil {
Init();
parent := mutate(target, 1.0);
iter := 0;
while(target->Equals(parent) <> true) {
rate := newMutateRate();
iter += 1;
if(iter % 100 = 0){
IO.Console->Instance()->Print(iter)->Print(": ")->PrintLine(parent);
};
bestSpawn : String;
bestFit := 0;
for(i := 0; i < C; i += 1;) {
spawn := mutate(parent, rate);
fitness := fitness(spawn);
if(fitness > bestFit) {
bestSpawn := spawn;
bestFit := fitness;
};
};
if(bestFit > fitness(parent)) {
parent := bestSpawn;
};
};
parent->PrintLine();
}
}
}
}</lang>
Output:
100: DETHILBMDEB QR YIEGYEBWCCSBN 200: D THIWTXEXH IO SVUDHEEWQASEL 300: DVTHINTILS RIO SVGEKNEWEASEU 400: MFTH AWBLIXNIE STFE AWWEASEJ 500: MFTHIAWDIIRMIY QTFE AWWEASEJ 600: MZTCIAKDQIRNIY NWFE A WEASEJ 700: MZTCIAKDQIRNIY NWFE A WEASEJ 800: MZTCIAKDQIRNIY NWFE A WEASEJ 900: MZTCIAKOWIRNIY NILE A WEASEJ 1000: MZTCIAKOWIRNIY NILE A WEASEJ 1100: MZTCIAKOWIRNIY NILE A WEASEJ 1200: MZTCIAKOWIRNIY NILE A WEASEJ 1300: METCITKSTIRSIY JYKE A WDASEJ 1400: METHITKSTIJ IB FYKE A WDASEJ 1500: METHINKSZIJ IB FYKE A WEASEQ METHINKS IT IS LIKE A WEASEL
OCaml
<lang ocaml>let target = "METHINKS IT IS LIKE A WEASEL" let charset = "ABCDEFGHIJKLMNOPQRSTUVWXYZ " let tlen = String.length target let clen = String.length charset let () = Random.self_init()
let parent =
let s = String.create tlen in for i = 0 to tlen-1 do s.[i] <- charset.[Random.int clen] done; s
let fitness ~trial =
let rec aux i d =
if i >= tlen then d else
aux (i+1) (if target.[i] = trial.[i] then d+1 else d) in
aux 0 0
let mutate parent rate =
let s = String.copy parent in
for i = 0 to tlen-1 do
if Random.float 1.0 > rate then
s.[i] <- charset.[Random.int clen]
done;
s, fitness s
let () =
let i = ref 0 in
while parent <> target do
let pfit = fitness parent in
let rate = float pfit /. float tlen in
let tries = Array.init 200 (fun _ -> mutate parent rate) in
let min_by (a, fa) (b, fb) = if fa > fb then a, fa else b, fb in
let best, f = Array.fold_left min_by (parent, pfit) tries in
if !i mod 100 = 0 then
Printf.printf "%5d - '%s' (fitness:%2d)\n%!" !i best f;
String.blit best 0 parent 0 tlen;
incr i
done;
Printf.printf "%5d - '%s'\n" !i parent</lang>
Octave
<lang octave>global target; target = split("METHINKS IT IS LIKE A WEASEL", ""); charset = ["A":"Z", " "]; p = ones(length(charset), 1) ./ length(charset); parent = discrete_rnd(charset, p, length(target), 1); mutaterate = 0.1;
C = 1000;
function r = fitness(parent, target)
r = sum(parent == target) ./ length(target);
endfunction
function r = mutate(parent, mutaterate, charset)
r = parent; p = unifrnd(0, 1, length(parent), 1); nmutants = sum( p < mutaterate ); if (nmutants) s = discrete_rnd(charset, ones(length(charset), 1) ./ length(charset),nmutants,1); r( p < mutaterate ) = s; endif
endfunction
function r = evolve(parent, mutatefunc, fitnessfunc, C, mutaterate, charset)
global target; children = []; for i = 1:C children = [children, mutatefunc(parent, mutaterate, charset)]; endfor children = [parent, children]; fitval = []; for i = 1:columns(children) fitval = [fitval, fitnessfunc(children(:,i), target)]; endfor [m, im] = max(fitval); r = children(:, im);
endfunction
function printgen(p, t, i)
printf("%3d %5.2f %s\n", i, fitness(p, t), p');
endfunction
i = 0;
while( !all(parent == target) )
i++; parent = evolve(parent, @mutate, @fitness, C, mutaterate, charset); if ( mod(i, 1) == 0 ) printgen(parent, target, i); endif
endwhile disp(parent'); </lang>
Oforth
<lang oforth>200 Constant new: C
5 Constant new: RATE
- randChar // -- c
27 rand dup 27 == ifTrue: [ drop ' ' ] else: [ 'A' + 1- ] ;
- fitness(a b -- n)
a b zipWith(#==) sum ;
- mutate(s -- s')
s map(#[ 100 rand RATE <= ifTrue: [ drop randChar ] ]) charsAsString ;
: evolve(target)
| parent |
ListBuffer init(target size, #randChar) charsAsString ->parent
1 while ( parent target <> ) [
ListBuffer init(C, #[ parent mutate ]) dup add(parent)
maxFor(#[ target fitness ]) dup ->parent . dup println 1+
] drop ;</lang>
- Output:
>evolve("METHINKS IT IS LIKE A WEASEL")
WHQHNXXAWACZKTTIHKVBCYLPATN 1
WHQHNXXAWACZKTTIHKV CYLPATN 2
WHQHNXXAWACZKTTIHKV C LPATC 3
WHQHNXXSWATZKTTIHKV C LPATC 4
WHQHNXXSWATCKTTIHKV C LEATC 5
WHQHNXXSWATCKTTIHKV C LEATCL 6
WHQHNXXSWATCKFTIHKV C LEASCL 7
WHQHNXXSWATCKF IHKV C LEASCL 8
WHQHNXXSWATZKF IHKV A LEASCL 9
MHQHNXXSWATZKF IHKV A LEASCL 10
MATHNXXSWATZKF ICKV A LEASCL 11
MATHIXXSBATZKF ICKV A LEASCL 12
MATHIXXSBATZKS ICKV A LEASCL 13
MATHIXXSBATZKS BCKV A LEASCL 14
MATHIXXSBATZKS LCKV A LEASCL 15
MATHIXXS ATZKS LSKV A LEASCL 16
MATHIXXS ATJKS LSKV A LEASEL 17
METHIXXS ATJKS LSKV A LEASEL 18
METHIXXS ATJKS LSKE A LEASEL 19
METHINXS ATJKS LSKE A LEASEL 20
METHINXS ATJKS LSKE A WEASEL 21
METHINKS ATJKS LSKE A WEASEL 22
METHINKS ATJUS LSKE A WEASEL 23
METHINKS ATJUS LSKE A WEASEL 24
METHINKS ATJIS LSKE A WEASEL 25
METHINKS ATJIS LSKE A WEASEL 26
METHINKS ATJIS LIKE A WEASEL 27
METHINKS ATJIS LIKE A WEASEL 28
METHINKS STJIS LIKE A WEASEL 29
METHINKS STJIS LIKE A WEASEL 30
METHINKS OT IS LIKE A WEASEL 31
METHINKS OT IS LIKE A WEASEL 32
METHINKS OT IS LIKE A WEASEL 33
METHINKS OT IS LIKE A WEASEL 34
METHINKS OT IS LIKE A WEASEL 35
METHINKS IT IS LIKE A WEASEL 36
ok
OoRexx
Run with Open Object Rexx 4.1.0 by IBM Corporation 1995,2004 Rexx LA 2005-2010. Host OS: Microsoft Windows 7. <lang oorexx> /* Weasel.rex - Me thinks thou art a weasel. - G,M.D. - 2/25/2011 */ arg C M /* C is the number of children parent produces each generation. */ /* M is the mutation rate of each gene (character) */
call initialize generation = 0 do until parent = target
most_fitness = fitness(parent)
most_fit = parent
do C
child = mutate(parent, M)
child_fitness = fitness(child)
if child_fitness > most_fitness then
do
most_fitness = child_fitness
most_fit = child
say "Generation" generation": most fit='"most_fit"', fitness="left(most_fitness,4)
end
end
parent = most_fit
generation = generation + 1
end exit
initialize:
target = "METHINKS IT IS LIKE A WEASEL"
alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ "
c_length_target = length(target)
parent = mutate(copies(" ", c_length_target), 1.0)
do i = 1 to c_length_target
target_ch.i = substr(target,i,1)
end
return
fitness: procedure expose target_ch. c_length_target
arg parm_string
fitness = 0
do i_target = 1 to c_length_target
if substr(parm_string,i_target,1) = target_ch.i_target then
fitness = fitness + 1
end
return fitness
mutate:procedure expose alphabet arg string, parm_mutation_rate
result = ""
do istr = 1 to length(string)
if random(1,1000)/1000 <= parm_mutation_rate then
result = result || substr(alphabet,random(1,length(alphabet)),1)
else
result = result || substr(string,istr,1)
end
return result </lang> Output:
C:\usr\rex>weasel 10 .01 Generation 20, most fit='BZTACOQCQ CTMPIXPXBVKRUCLY F', fitness=1 Generation 30, most fit='BZTHCOQCQ CTMPIXPXBVKRUCLY F', fitness=2 Generation 34, most fit='BZTHCOQSQ CTMPIXPXBVKRUCLY F', fitness=3 Generation 61, most fit='BZTHCOQSQ CTIPIXPXBVKRUCLY F', fitness=4 Generation 95, most fit='BZTHCNQSQ CTIPIXPXBVKRUCLY F', fitness=5 Generation 107, most fit='BZTHCNQSQ CTISIXPXBVKRUCLY F', fitness=6 Generation 121, most fit='BZTHCNQS CTISIXPXBVKRUCLY F', fitness=7 Generation 129, most fit='BZTHCNQS CTISIXPXBVKRUELY F', fitness=8 Generation 142, most fit='BZTHCNQS CTISIXPXBVKRUELS F', fitness=9 Generation 143, most fit='BZTHCNQS ICTISIXPXBVKRUEHS F', fitness=10 Generation 147, most fit='BZTHCNQS ICTISIXPXBVKRUEHS L', fitness=11 Generation 154, most fit='BZTHCNQS IC ISIXPXBVKRUEHS L', fitness=12 Generation 201, most fit='BZTHCNQS IT ISIXPXBVKRUEHS L', fitness=13 Generation 213, most fit='BZTHCNQS IT ISIXPXEVKRUEHS L', fitness=14 Generation 250, most fit='BZTHCNKS IT ISIXPXEVKRUEHS L', fitness=15 Generation 268, most fit='BZTHCNKS IT ISIXPXEVKFUEAS L', fitness=16 Generation 274, most fit='BZTHCNKS IT ISIXPKEVKFUEAS L', fitness=17 Generation 292, most fit='BZTHCNKS IT ISIXPKEVKFWEAS L', fitness=18 Generation 353, most fit='BZTHCNKS IT ISIXPKEVKFWEASEL', fitness=19 Generation 358, most fit='BZTHCNKS IT ISIXPKEVK WEASEL', fitness=20 Generation 374, most fit='BETHCNKS IT ISIXPKEVK WEASEL', fitness=21 Generation 404, most fit='BETHCNKS IT ISILPKEVK WEASEL', fitness=22 Generation 405, most fit='BETHCNKS IT ISILPKE K WEASEL', fitness=23 Generation 448, most fit='FETHCNKS IT ISILPKE A WEASEL', fitness=24 Generation 679, most fit='FETHINKS IT ISILPKE A WEASEL', fitness=25 Generation 964, most fit='METHINKS IT ISILPKE A WEASEL', fitness=26 Generation 1018, most fit='METHINKS IT ISILIKE A WEASEL', fitness=27 Generation 1250, most fit='METHINKS IT IS LIKE A WEASEL', fitness=28 C:\usr\rex>
OxygenBasic
The algorithm pared down to the essentials. It takes around 1200 to 6000 mutations to attain the target. Fitness is measured by the number of beneficial mutations. The cycle ends when this is equal to the string length. <lang oxygenbasic>
'EVOLUTION
target="METHINKS IT IS LIKE A WEASEL" le=len target progeny=string le,"X"
quad seed declare QueryPerformanceCounter lib "kernel32.dll" (quad*q) QueryPerformanceCounter seed
Function Rand(sys max) as sys
mov eax,max inc eax imul edx,seed,0x8088405 inc edx mov seed,edx mul edx return edx
End Function
sys ls=le-1,cp=0,ct=0,ch=0,fit=0,gens=0
do '1 mutation per generation
i=1+rand ls 'mutation position
ch=64+rand 26 'mutation ascii code
if ch=64 then ch=32 'change '@' to ' '
ct=asc target,i 'target ascii code
cp=asc progeny,i 'parent ascii code
'
if ch=ct then
if cp<>ct then
mid progeny,i,chr ch 'carry improvement
fit++ 'increment fitness
end if
end if
gens++
if fit=le then exit do 'matches target
end do print progeny " " gens 'RESULT (range 1200-6000 generations) </lang>
Oz
<lang oz>declare
Target = "METHINKS IT IS LIKE A WEASEL"
C = 100
MutateRate = 5 %% percent
proc {Main}
X0 = {MakeN {Length Target} RandomChar}
in
for Xi in {Iterate Evolve X0} break:Break do
{System.showInfo Xi}
if Xi == Target then {Break} end
end
end
fun {Evolve Xi}
Copies = {MakeN C fun {$} {Mutate Xi} end}
in
{FoldL Copies MaxByFitness Xi}
end
fun {Mutate Xs}
{Map Xs
fun {$ X}
if {OS.rand} mod 100 < MutateRate then {RandomChar}
else X
end
end}
end
fun {MaxByFitness A B}
if {Fitness B} > {Fitness A} then B else A end
end
fun {Fitness Candidate}
{Length {Filter {List.zip Candidate Target Value.'=='} Id}}
end
Alphabet = & |{List.number &A &Z 1}
fun {RandomChar}
I = {OS.rand} mod {Length Alphabet} + 1
in
{Nth Alphabet I}
end
%% General purpose helpers
fun {Id X} X end
fun {MakeN N F}
Xs = {List.make N}
in
{ForAll Xs F}
Xs
end
fun lazy {Iterate F X}
X|{Iterate F {F X}}
end
in
{Main}</lang>
PARI/GP
The algorithm given here is more general than the one described, in which letters can be inserted or deleted as well as mutated. The rate for insertions and deletions are set to 0, however, so the results are the same.
This code is inefficient (tens of milliseconds) since it converts back and forth between string and vector format. A more efficient version would keep the information in a Vecsmall instead. <lang parigp>target="METHINKS IT IS LIKE A WEASEL"; fitness(s)=-dist(Vec(s),Vec(target)); dist(u,v)=sum(i=1,min(#u,#v),u[i]!=v[i])+abs(#u-#v); letter()=my(r=random(27)); if(r==26, " ", Strchr(r+65)); insert(v,x=letter())= { my(r=random(#v+1)); if(r==0, return(concat([x],v))); if(r==#v, return(concat(v,[x]))); concat(concat(v[1..r],[x]),v[r+1..#v]); } delete(v)= { if(#v<2, return([])); my(r=random(#v)+1); if(r==1, return(v[2..#v])); if(r==#v, return(v[1..#v-1])); concat(v[1..r-1],v[r+1..#v]); } mutate(s,rateM,rateI,rateD)= { my(v=Vec(s)); if(random(1.)<rateI, v=insert(v)); if(random(1.)<rateD, v=delete(v)); for(i=1,#v, if(random(1.)<rateM, v[i]=letter()) ); concat(v); } evolve(C,rate)= { my(parent=concat(vector(#target,i,letter())),ct=0); while(parent != target, print(parent" "fitness(parent)); my(v=vector(C,i,mutate(parent,rate,0,0)),best,t); best=fitness(parent=v[1]); for(i=2,C, t=fitness(v[i]); if(t>best, best=t; parent=v[i]) ); ct++ ); print(parent" "fitness(parent)); ct; } evolve(35,.05)</lang>
Pascal
This Pascal version of the program displays the initial random string and every hundredth generation after that. It also displays the final generation count. Mutation happens relatively slowly, about once in every 1000 characters, but this can be changed by altering the RATE constant. Lower values for RATE actually speed up the mutations.
<lang pascal>PROGRAM EVOLUTION (OUTPUT);
CONST TARGET = 'METHINKS IT IS LIKE A WEASEL'; COPIES = 100; (* 100 children in each generation. *) RATE = 1000; (* About one character in 1000 will be a mutation. *)
TYPE STRLIST = ARRAY [1..COPIES] OF STRING;
FUNCTION RANDCHAR : CHAR;
(* Generate a random letter or space. *) VAR RANDNUM : INTEGER; BEGIN
RANDNUM := RANDOM(27); IF RANDNUM = 26 THEN RANDCHAR := ' ' ELSE RANDCHAR := CHR(RANDNUM + ORD('A'))
END;
FUNCTION RANDSTR (SIZE : INTEGER) : STRING;
(* Generate a random string. *) VAR
N : INTEGER; S : STRING;
BEGIN
S := ; FOR N := 1 TO SIZE DO INSERT(RANDCHAR, S, 1); RANDSTR := S
END;
FUNCTION FITNESS (CANDIDATE, GOAL : STRING) : INTEGER;
(* Count the number of correct letters in the correct places *) VAR N, MATCHES : INTEGER; BEGIN
MATCHES := 0; FOR N := 1 TO LENGTH(GOAL) DO IF CANDIDATE[N] = GOAL[N] THEN MATCHES := MATCHES + 1; FITNESS := MATCHES
END;
FUNCTION MUTATE (RATE : INTEGER; S : STRING) : STRING;
(* Randomly alter a string. Characters change with probability 1/RATE. *) VAR
N : INTEGER; CHANGE : BOOLEAN;
BEGIN
FOR N := 1 TO LENGTH(TARGET) DO BEGIN CHANGE := RANDOM(RATE) = 0; IF CHANGE THEN S[N] := RANDCHAR END; MUTATE := S
END;
PROCEDURE REPRODUCE (RATE : INTEGER; PARENT : STRING; VAR CHILDREN : STRLIST);
(* Generate children with random mutations. *) VAR N : INTEGER; BEGIN
FOR N := 1 TO COPIES DO CHILDREN[N] := MUTATE(RATE, PARENT)
END;
FUNCTION FITTEST(CHILDREN : STRLIST; GOAL : STRING) : STRING;
(* Measure the fitness of each child and return the fittest. *) (* If multiple children equally match the target, then return the first. *) VAR
MATCHES, MOST_MATCHES, BEST_INDEX, N : INTEGER;
BEGIN
MOST_MATCHES := 0; BEST_INDEX := 1; FOR N := 1 TO COPIES DO BEGIN MATCHES := FITNESS(CHILDREN[N], GOAL); IF MATCHES > MOST_MATCHES THEN BEGIN MOST_MATCHES := MATCHES; BEST_INDEX := N END END; FITTEST := CHILDREN[BEST_INDEX]
END;
VAR PARENT, BEST_CHILD : STRING; CHILDREN : STRLIST; GENERATIONS : INTEGER;
BEGIN RANDOMIZE; GENERATIONS := 0; PARENT := RANDSTR(LENGTH(TARGET)); WHILE NOT (PARENT = TARGET) DO BEGIN IF (GENERATIONS MOD 100) = 0 THEN WRITELN(PARENT); GENERATIONS := GENERATIONS + 1; REPRODUCE(RATE, PARENT, CHILDREN); BEST_CHILD := FITTEST(CHILDREN, TARGET); IF FITNESS(PARENT, TARGET) < FITNESS(BEST_CHILD, TARGET) THEN PARENT := BEST_CHILD END; WRITE('The string was matched in '); WRITELN(GENERATIONS, ' generations.') END.</lang>
Perl
This implementation usually converges in less than 70 iterations.
<lang perl>use List::Util 'reduce'; use List::MoreUtils 'false';
- Generally useful declarations
sub randElm
{$_[int rand @_]}
sub minBy (&@)
{my $f = shift;
reduce {$f->($b) < $f->($a) ? $b : $a} @_;}
sub zip
{@_ or return ();
for (my ($n, @a) = 0 ;; ++$n)
{my @row;
foreach (@_)
{$n < @$_ or return @a;
push @row, $_->[$n];}
push @a, \@row;}}
- Task-specific declarations
my $C = 100; my $mutation_rate = .05; my @target = split , 'METHINKS IT IS LIKE A WEASEL'; my @valid_chars = (' ', 'A' .. 'Z');
sub fitness
{false {$_->[0] eq $_->[1]} zip shift, \@target;}
sub mutate
{my $rate = shift;
return [map {rand() < $rate ? randElm @valid_chars : $_} @{shift()}];}
- Main loop
my $parent = [map {randElm @valid_chars} @target];
while (fitness $parent)
{$parent =
minBy \&fitness,
map {mutate $mutation_rate, $parent}
1 .. $C;
print @$parent, "\n";}</lang>
Phix
with javascript_semantics constant target = "METHINKS IT IS LIKE A WEASEL", AZS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ ", C = 5000, -- children in each generation P = 15 -- probability of mutation (1 in 15) function fitness(string sample, string target) return sum(sq_eq(sample,target)) end function function mutate(string s, integer n) for i=1 to length(s) do if rand(n)=1 then s[i] = AZS[rand(length(AZS))] end if end for return s end function string parent = mutate(target,1) -- (mutate with 100% probability) sequence samples = repeat(0,C) integer gen = 0, best, fit, best_fit = fitness(parent,target) while parent!=target do printf(1,"Generation%3d: %s, fitness %3.2f%%\n", {gen, parent, (best_fit/length(target))*100}) best_fit = -1 for i=1 to C do samples[i] = mutate(parent, P) fit = fitness(samples[i], target) if fit > best_fit then best_fit = fit best = i end if end for parent = samples[best] gen += 1 end while printf(1,"Finally, \"%s\"\n",{parent})
- Output:
Generation 0: NKY NWLYBJOPOJFE RRISKGJD RS, fitness 0.00% Generation 1: NKYHNNLYAIOPOJFE ERISKGJD RS, fitness 10.71% Generation 2: NKYHNNLYAIOPOJFEIER SKGJD RS, fitness 17.86% Generation 3: IKYHNNLSAIOPOJFLIER SKGJW RS, fitness 25.00% Generation 4: MKTHNNLSAIOPOJILIER SKGJW RS, fitness 32.14% Generation 5: MKTHNNLSAITFOJILIEE SKGJW RS, fitness 39.29% Generation 6: MKTHONLSAITFOJILIEE SKGJW EL, fitness 46.43% Generation 7: MKTHINLSAITFIJILIIE SKJJW EL, fitness 53.57% Generation 8: MKTHINLSAITFIS LIIE SKJJW EL, fitness 60.71% Generation 9: MKTHINLSAITFIS LIKE AKJJW EL, fitness 67.86% Generation 10: MKTHINLSAITFIS LIKE AKJEA EL, fitness 75.00% Generation 11: METHINLSAIT IS LIKE AKJEA EL, fitness 82.14% Generation 12: METHINLSAIT IS LIKE AKWEA EL, fitness 85.71% Generation 13: METHINLS IT IS LIKE AKWEA EL, fitness 89.29% Generation 14: METHINLS IT IS LIKE A WEA EL, fitness 92.86% Generation 15: METHINLS IT IS LIKE A WEASEL, fitness 96.43% Finally, "METHINKS IT IS LIKE A WEASEL"
PHP
<lang php> define('TARGET','METHINKS IT IS LIKE A WEASEL'); define('TBL','ABCDEFGHIJKLMNOPQRSTUVWXYZ ');
define('MUTATE',15); define('COPIES',30); define('TARGET_COUNT',strlen(TARGET)); define('TBL_COUNT',strlen(TBL));
// Determine number of different chars between a and b
function unfitness($a,$b) {
$sum=0;
for($i=0;$i<strlen($a);$i++)
if($a[$i]!=$b[$i]) $sum++;
return($sum);
}
function mutate($a) {
$tbl=TBL;
for($i=0;$i<strlen($a);$i++) $out[$i]=mt_rand(0,MUTATE)?$a[$i]:$tbl[mt_rand(0,TBL_COUNT-1)];
return(implode(,$out));
}
$tbl=TBL;
for($i=0;$i<TARGET_COUNT;$i++) $tspec[$i]=$tbl[mt_rand(0,TBL_COUNT-1)];
$parent[0]=implode(,$tspec);
$best=TARGET_COUNT+1;
$iters=0;
do {
for($i=1;$i<COPIES;$i++) $parent[$i]=mutate($parent[0]);
for($best_i=$i=0; $i<COPIES;$i++) {
$unfit=unfitness(TARGET,$parent[$i]);
if($unfit < $best || !$i) {
$best=$unfit;
$best_i=$i;
}
}
if($best_i>0) $parent[0]=$parent[$best_i];
$iters++;
print("Generation $iters, score $best: $parent[0]\n");
} while($best);
</lang> Sample Output:
Generation 1, score 25: IIVHUVOC NRGYBUEXLF LXZ SGMT Generation 2, score 24: MIVHUVOC MKGYBUEXLF LXZ HGMT Generation 3, score 24: MIVHUVOC MKGYBUEXLF LXZ HGMT ... Generation 177, score 1: METHQNKS IT IS LIKE A WEASEL Generation 178, score 0: METHINKS IT IS LIKE A WEASEL
PicoLisp
This example uses 'gen', the genetic function in "lib/simul.l" <lang PicoLisp>(load "@lib/simul.l")
(setq *Target (chop "METHINKS IT IS LIKE A WEASEL"))
- Generate random character
(de randChar ()
(if (=0 (rand 0 26))
" "
(char (rand `(char "A") `(char "Z"))) ) )
- Fitness function (Hamming distance)
(de fitness (A)
(cnt = A *Target) )
- Genetic algorithm
(gen
(make # Parent population
(do 100 # C = 100 children
(link
(make
(do (length *Target)
(link (randChar)) ) ) ) ) )
'((A) # Termination condition
(prinl (maxi fitness A)) # Print the fittest element
(member *Target A) ) # and check if solution is found
'((A B) # Recombination function
(mapcar
'((C D) (if (rand T) C D)) # Pick one of the chars
A B ) )
'((A) # Mutation function
(mapcar
'((C)
(if (=0 (rand 0 10)) # With a proability of 10%
(randChar) # generate a new char, otherwise
C ) ) # return the current char
A ) )
fitness ) # Selection function</lang>
Output:
RQ ASLWWWI ANSHPNABBAJ ZLTKX DETGGNGHWITIKSXLIIEBA WAATPC CETHINWS ITKESQGIKE A WSAGHO METHBNWS IT NSQLIKE A WEAEWL METHINKS IT ISCLIKE A WVASEL METHINKS IT ISOLIKE A WEASEL METHINKS IT IS LIKE A WEASEL
Pike
C is not used because i found it has no effect on the number of mutations needed to find the solution. in difference to the proposal, rate is not set as a percentage but as the number of characters to mutate when generating an offspring.
the rate is fixed at 2 as that is the lowest most successful rate still in the spirit of the original proposal (where mutation allows a previously successful change to be undone). if the rate is 1 than every successful character change can not change again (because it would not cause an improvement and thus be rejected.)
<lang Pike>string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ ";
string mutate(string data, int rate) {
array(int) alphabet=(array(int))chars;
multiset index = (multiset)enumerate(sizeof(data));
while(rate)
{
int pos = random(index);
data[pos]=random(alphabet);
rate--;
}
return data;
}
int fitness(string input, string target) {
return `+(@`==(((array)input)[*], ((array)target)[*]));
}
void main() {
array(string) alphabet = chars/""; string target = "METHINKS IT IS LIKE A WEASEL"; string parent = "";
while(sizeof(parent) != sizeof(target))
{
parent += random(alphabet);
}
int count;
write(" %5d: %s\n", count, parent);
while (parent != target)
{
string child = mutate(parent, 2);
count++;
if (fitness(child, target) > fitness(parent, target))
{
write(" %5d: %s\n", count, child);
parent = child;
}
}
}</lang>
Output:
0: TIRABZB IGVG TDXTGODFOXO UPU
2: TIRABZB IGVG TDXTGO FOXOTUPU
32: TIRABZB IGVG T XTGO FOXOTUPU
39: TIRABZB IGVG T JTGO AOXOTUPU
44: TIRABNB IGMG T JTGO AOXOTUPU
57: TIRABNB IGMG T ITGO AOXOTSPU
62: TISHBNB IGMG T ITGO AOXOTSPU
63: TISHBNB IGM T ITGO AOXONSPU
74: TISHBNB GM T ITGO AOHONSPU
89: TISHBNB GM S ITGO AYHONSPU
111: TISHBNB GM S ITGO AYHOASPU
112: MISHBNB GM S ITGO AYHUASPU
145: MISHBNBG IM S ITGO AYHUASPU
169: MISHBNBG IM NS ITGO AYHEASPU
182: MESHBNBG IM NS ATGO AYHEASPU
257: MESHBNBG ID NS ATGO A HEASPU
320: MESHBNBG ID NS LRGO A HEASPU
939: MESHINBG ID NS LRGO A HEASPU
1134: MESHINBG ID NS LRZO A HEASEU
1264: MESHINBG ID US LIZO A HEASEU
1294: MEYHINBG IT US LIZO A HEASEU
1507: MEYHINBG IT US LIZO A HEASEL
1823: METHINBG IT US LIZO A HEASEL
2080: METHINBG IT US LI E A HEASEL
2143: METHINBG IT IS LI E A HEASEL
3118: METHINWG IT IS LIKE A HEASEL
3260: METHINWC IT IS LIKE A WEASEL
3558: METHINWS IT IS LIKE A WEASEL
4520: METHINKS IT IS LIKE A WEASEL
Pony
<lang Pony>use "random"
actor Main
let _env: Env
let _rand: MT = MT // Mersenne Twister
let _target: String = "METHINKS IT IS LIKE A WEASEL"
let _possibilities: String = "ABCDEFGHIJKLMNOPQRSTUVWXYZ "
let _c: U16 = 100 // number of spawn per generation
let _min_mutate_rate: F64 = 0.09
let _perfect_fitness: USize = _target.size()
var _parent: String = ""
new create(env: Env) =>
_env = env
_parent = mutate(_target, 1.0)
var iter: U64 = 0
while not _target.eq(_parent) do
let rate: F64 = new_mutate_rate()
iter = iter + 1
if (iter % 100) == 0 then
_env.out.write(iter.string() + ": " + _parent)
_env.out.write(", fitness: " + fitness(_parent).string())
_env.out.print(", rate: " + rate.string())
end
var best_spawn = ""
var best_fit: USize = 0
var i: U16 = 0
while i < _c do
let spawn = mutate(_parent, rate)
let spawn_fitness = fitness(spawn)
if spawn_fitness > best_fit then
best_spawn = spawn
best_fit = spawn_fitness
end
i = i + 1
end
if best_fit > fitness(_parent) then
_parent = best_spawn
end
end
_env.out.print(_parent + ", " + iter.string())
fun fitness(trial: String): USize =>
var ret_val: USize = 0
var i: USize = 0
while i < trial.size() do
try
if trial(i)? == _target(i)? then
ret_val = ret_val + 1
end
end
i = i + 1
end
ret_val
fun new_mutate_rate(): F64 => let perfect_fit = _perfect_fitness.f64() ((perfect_fit - fitness(_parent).f64()) / perfect_fit) * (1.0 - _min_mutate_rate)
fun ref mutate(parent: String box, rate: F64): String =>
var ret_val = recover trn String end
for char in parent.values() do
let rnd_real: F64 = _rand.real()
if rnd_real <= rate then
let rnd_int: U64 = _rand.int(_possibilities.size().u64())
try
ret_val.push(_possibilities(rnd_int.usize())?)
end
else
ret_val.push(char)
end
end
consume ret_val</lang>
Output:
100: UMMMDNKR IEIIB IIKZ A THAHEL, fitness: 14, rate: 0.455 200: UMMMDNKR IEIIB IIKZ A THAHEL, fitness: 14, rate: 0.455 300: KMHJZNKS IUIIS IISQ A TWASEL, fitness: 16, rate: 0.39 400: KHHHCNKS IT I CIKE A XFASEL, fitness: 20, rate: 0.26 500: MINHINKS IT IS LIKE A WEASEL, fitness: 26, rate: 0.065 METHINKS IT IS LIKE A WEASEL, 526
Alternative solution:
Using a more OO approach that leverages classes for encapsulation.
<lang Pony>use "random"
use "collections"
class CreationFactory
let _desired: String
new create(d: String) => _desired = d
fun apply(c: String): Creation => Creation(c, _fitness(c))
fun _fitness(s: String): USize =>
var f = USize(0)
for i in Range(0, s.size()) do
try
if s(i)? == _desired(i)? then
f = f +1
end
end
end
f
class val Creation
let string: String let fitness: USize
new val create(s: String = "", f: USize = 0) => string = s fitness = f
class Mutator
embed _rand: MT = MT let _possibilities: String = "ABCDEFGHIJKLMNOPQRSTUVWXYZ " let _cf: CreationFactory
new create(cf: CreationFactory) => _cf = cf
fun ref apply(parent: Creation, rate: F64): Creation => let ns = _new_string(parent.string, rate) _cf(ns)
fun ref _new_string(parent: String, rate: F64): String =>
var mutated = recover String(parent.size()) end
for char in parent.values() do
mutated.push(_mutate_letter(char, rate))
end
consume mutated
fun ref _mutate_letter(current: U8, rate: F64): U8 =>
if _rand.real() <= rate then
_random_letter()
else
current
end
fun ref _random_letter(): U8 => let ln = _rand.int(_possibilities.size().u64()).usize() try _possibilities(ln)? else ' ' end
class Generation
let _size: USize let _desired: Creation let _mutator: Mutator
new create(size: USize = 100, desired: Creation, mutator: Mutator) => _size = size _desired = desired _mutator = consume mutator
fun ref apply(parent: Creation): Creation =>
var best = parent
let mutation_rate = _mutation_rate(best)
for i in Range(0, _size) do
let candidate = _mutator(best, mutation_rate)
if candidate.fitness > best.fitness then
best = candidate
end
end
best
fun _mutation_rate(best: Creation): F64 => let min_mutate_rate: F64 = 0.09
let df = _desired.fitness.f64() let bf = best.fitness.f64()
((df - bf) / df) * (1.0 - min_mutate_rate)
actor Main
new create(env: Env) => let d = "METHINKS IT IS LIKE A WEASEL" let cf = CreationFactory(d) let desired = cf(d) let mutator = Mutator(cf) let start = mutator(desired, 1.0) let spawn_per_generation = USize(100)
var iterations = U64(0) var best = start
repeat
best = Generation(spawn_per_generation, desired, mutator)(best)
iterations = iterations + 1
if (iterations % 100) == 0 then
env.out.print(
iterations.string() + ": "
+ best.string + ", fitness: " + best.fitness.string()
)
end
until best.string == desired.string end
env.out.print(best.string + ", " + iterations.string())</lang>
Output:
100: MELWILYSH TDKKTPIKE DXWEASKL, fitness: 14 200: MEMHINTSLLT M KPFKETN WEASHL, fitness: 16 300: MQTHINFS ET MT DIKEVA WEASEL, fitness: 21 400: METHINKS IT IS DIKEDA WEASEL, fitness: 26 METHINKS IT IS LIKE A WEASEL, 442
Prolog
<lang Prolog>target("METHINKS IT IS LIKE A WEASEL").
rndAlpha(64, 32). % Generate a single random character rndAlpha(P, P). % 32 is a space, and 65->90 are upper case rndAlpha(Ch) :- random(N), P is truncate(64+(N*27)), !, rndAlpha(P, Ch).
rndTxt(0, []). % Generate some random text (fixed length) rndTxt(Len, [H|T]) :- succ(L, Len), rndAlpha(H), !, rndTxt(L, T).
score([], [], Score, Score). % Score a generated mutation (count diffs) score([Ht|Tt], [Ht|Tp], C, Score) :- !, score(Tt, Tp, C, Score). score([_|Tt], [_|Tp], C, Score) :- succ(C, N), !, score(Tt, Tp, N, Score). score(Txt, Score, Target) :- !, score(Target, Txt, 0, Score).
mutate(_, [], []). % mutate(Probability, Input, Output) mutate(P, [H|Txt], [H|Mut]) :- random(R), R < P, !, mutate(P, Txt, Mut). mutate(P, [_|Txt], [M|Mut]) :- rndAlpha(M), !, mutate(P, Txt, Mut).
weasel(Tries, _, _, mutation(0, Result)) :- % No differences=success format('~w~4|:~w~3| - ~s\n', [Tries, 0, Result]). weasel(Tries, Chance, Target, mutation(S, Value)) :- % output progress format('~w~4|:~w~3| - ~s\n', [Tries, S, Value]), !, % and call again weasel(Tries, Chance, Target, Value). weasel(Tries, Chance, Target, Start) :- findall(mutation(S,M), % Generate 30 mutations, select the best. (between(1, 30, _), mutate(Chance, Start, M), score(M,S,Target)), Mutations), % List of 30 mutations and their scores sort(Mutations, [Best|_]), succ(Tries, N), !, weasel(N, Chance, Target, Best). weasel :- % Chance->probability for a mutation, T=Target, Start=initial text target(T), length(T, Len), rndTxt(Len, Start), Chance is 1 - (1/(Len+1)), !, weasel(0, Chance, T, Start).</lang> Output:
time(weasel). 1 :27 - SGR JDTLWJQNGFOEJNQTVQOJLEEV 2 :27 - SGR DDTLWJQNGFOEJNQTVQOJLEEV 3 :26 - SGR DDTLWJQNGFHEJNQTVQOJLSEV 4 :25 - MGR DDWLWJQNGFHEJDQTVQOJLSEV 5 :24 - MGR DDWL JQNGFHEJDQTVQOJLSEV 6 :24 - MGR DBWL JQNGFHEJUQTVQOJLSEV 7 :23 - MRR IBWL JQNGFHEJUQTVFOJLSEV ... 168 :1 - METHINKS IT I LIKE A WEASEL 169 :1 - METHINKS IT I LIKE A WEASEL 170 :1 - METHINKS IT I LIKE A WEASEL 171 :1 - METHINKS IT I LIKE A WEASEL 172 :1 - METHINKS IT I LIKE A WEASEL 173 :0 - METHINKS IT IS LIKE A WEASEL % 810,429 inferences, 0.125 CPU in 0.190 seconds (66% CPU, 6493780 Lips) true
PureBasic
<lang PureBasic>Define population = 100, mutationRate = 6 Define.s target$ = "METHINKS IT IS LIKE A WEASEL" Define.s charSet$ = "ABCDEFGHIJKLMNOPQRSTUVWXYZ "
Procedure.i fitness(Array aspirant.c(1), Array target.c(1))
Protected i, len, fit len = ArraySize(aspirant()) For i = 0 To len If aspirant(i) = target(i): fit +1: EndIf Next ProcedureReturn fit
EndProcedure
Procedure mutatae(Array parent.c(1), Array child.c(1), Array charSetA.c(1), rate.i)
Protected i, L, maxC
L = ArraySize(child())
maxC = ArraySize(charSetA())
For i = 0 To L
If Random(100) < rate
child(i) = charSetA(Random(maxC))
Else
child(i) = parent(i)
EndIf
Next
EndProcedure
Procedure.s cArray2string(Array A.c(1))
Protected S.s, len len = ArraySize(A())+1 : S = Space(len) CopyMemory(@A(0), @S, len * SizeOf(Character)) ProcedureReturn S
EndProcedure
Define mutationRate, maxChar, target_len, i, maxfit, gen, fit, bestfit Dim targetA.c(Len(target$) - 1) CopyMemory(@target$, @targetA(0), StringByteLength(target$))
Dim charSetA.c(Len(charSet$) - 1) CopyMemory(@charSet$, @charSetA(0), StringByteLength(charSet$))
maxChar = Len(charSet$) - 1 maxfit = Len(target$) target_len = Len(target$) - 1 Dim parent.c(target_len) Dim child.c(target_len) Dim Bestchild.c(target_len)
For i = 0 To target_len
parent(i) = charSetA(Random(maxChar))
Next
fit = fitness (parent(), targetA()) OpenConsole()
PrintN(Str(gen) + ": " + cArray2string(parent()) + ": Fitness= " + Str(fit) + "/" + Str(maxfit))
While bestfit <> maxfit
gen + 1
For i = 1 To population
mutatae(parent(),child(),charSetA(), mutationRate)
fit = fitness (child(), targetA())
If fit > bestfit
bestfit = fit: CopyArray(child(), Bestchild())
EndIf
Next
CopyArray(Bestchild(), parent())
PrintN(Str(gen) + ": " + cArray2string(parent()) + ": Fitness= " + Str(bestfit) + "/" + Str(maxfit))
Wend
PrintN("Press any key to exit"): Repeat: Until Inkey() <> ""</lang>
Python
Using lists instead of strings for easier manipulation, and a mutation rate that gives more mutations the further the parent is away from the target. <lang python>from string import letters from random import choice, random
target = list("METHINKS IT IS LIKE A WEASEL") charset = letters + ' ' parent = [choice(charset) for _ in range(len(target))] minmutaterate = .09 C = range(100)
perfectfitness = float(len(target))
def fitness(trial):
'Sum of matching chars by position' return sum(t==h for t,h in zip(trial, target))
def mutaterate():
'Less mutation the closer the fit of the parent' return 1-((perfectfitness - fitness(parent)) / perfectfitness * (1 - minmutaterate))
def mutate(parent, rate):
return [(ch if random() <= rate else choice(charset)) for ch in parent]
def que():
'(from the favourite saying of Manuel in Fawlty Towers)'
print ("#%-4i, fitness: %4.1f%%, '%s'" %
(iterations, fitness(parent)*100./perfectfitness, .join(parent)))
def mate(a, b):
place = 0
if choice(xrange(10)) < 7:
place = choice(xrange(len(target)))
else:
return a, b
return a, b, a[:place] + b[place:], b[:place] + a[place:]
iterations = 0 center = len(C)/2 while parent != target:
rate = mutaterate() iterations += 1 if iterations % 100 == 0: que() copies = [ mutate(parent, rate) for _ in C ] + [parent] parent1 = max(copies[:center], key=fitness) parent2 = max(copies[center:], key=fitness) parent = max(mate(parent1, parent2), key=fitness)
que()</lang>
Sample output
#100 , fitness: 50.0%, 'DVTAIKKS OZ IAPYIKWXALWE CEL' #200 , fitness: 60.7%, 'MHUBINKMEIG IS LIZEVA WEOPOL' #300 , fitness: 71.4%, 'MEYHINKS ID SS LIJF A KEKUEL' #378 , fitness: 100.0%, 'METHINKS IT IS LIKE A WEASEL'
A simpler Python version that converges in less steps: <lang python>from random import choice, random
target = list("METHINKS IT IS LIKE A WEASEL") alphabet = " ABCDEFGHIJLKLMNOPQRSTUVWXYZ" p = 0.05 # mutation probability c = 100 # number of children in each generation
def neg_fitness(trial):
return sum(t != h for t,h in zip(trial, target))
def mutate(parent):
return [(choice(alphabet) if random() < p else ch) for ch in parent]
parent = [choice(alphabet) for _ in xrange(len(target))] i = 0 print "%3d" % i, "".join(parent) while parent != target:
copies = (mutate(parent) for _ in xrange(c)) parent = min(copies, key=neg_fitness) print "%3d" % i, "".join(parent) i += 1</lang>
R
<lang R>set.seed(1234, kind="Mersenne-Twister")
- Easier if the string is a character vector
target <- unlist(strsplit("METHINKS IT IS LIKE A WEASEL", ""))
charset <- c(LETTERS, " ") parent <- sample(charset, length(target), replace=TRUE)
mutaterate <- 0.01
- Number of offspring in each generation
C <- 100
- Hamming distance between strings normalized by string length is used
- as the fitness function.
fitness <- function(parent, target) {
sum(parent == target) / length(target)
}
mutate <- function(parent, rate, charset) {
p <- runif(length(parent))
nMutants <- sum(p < rate)
if (nMutants) {
parent[ p < rate ] <- sample(charset, nMutants, replace=TRUE)
}
parent
}
evolve <- function(parent, mutate, fitness, C, mutaterate, charset) {
children <- replicate(C, mutate(parent, mutaterate, charset),
simplify=FALSE)
children <- c(list(parent), children)
childrenwhich.max(sapply(children, fitness, target=target))
}
.printGen <- function(parent, target, gen) {
cat(format(i, width=3),
formatC(fitness(parent, target), digits=2, format="f"),
paste(parent, collapse=""), "\n")
}
i <- 0 .printGen(parent, target, i) while ( ! all(parent == target)) {
i <- i + 1 parent <- evolve(parent, mutate, fitness, C, mutaterate, charset)
if (i %% 20 == 0) {
.printGen(parent, target, i)
}
} .printGen(parent, target, i)</lang>
output:
0 0.00 DQQQXRAGRNSOHYHWHHFGIIEBFVOY 20 0.36 MQQQXBAS TTOHSHLHKF I ABFSOY 40 0.71 MQTHINKS TTXHSHLIKE A WBFSEY 60 0.82 METHINKS IT HSHLIKE A WBFSEY 80 0.93 METHINKS IT HS LIKE A WEFSEL 99 1.00 METHINKS IT IS LIKE A WEASEL
Alternative
Very close to former solution, but a bit easier.
<lang R># Setup set.seed(42) target= unlist(strsplit("METHINKS IT IS LIKE A WEASEL", "")) chars= c(LETTERS, " ") C= 100
- Fitness function; high value means higher fitness
fitness= function(x){
sum(x == target)
}
- Mutate function
mutate= function(x, rate= 0.01){
idx= which(runif(length(target)) <= rate) x[idx]= replicate(n= length(idx), expr= sample(x= chars, size= 1, replace= T)) x
}
- Evolve function
evolve= function(x){
parents= rep(list(x), C+1) # Repliction parents[1:C]= lapply(parents[1:C], function(x) mutate(x)) # Mutation idx= which.max(lapply(parents, function(x) fitness(x))) # Selection parentsidx
}
- Initialize first parent
parent= sample(x= chars, size= length(target), replace= T)
- Main program
while (fitness(parent) < fitness(target)) {
parent= evolve(parent) cat(paste0(parent, collapse=""), "\n")
}</lang>
output:
YEHWROTERTMEZGMZ DMPYD ZCNKY ... METHINKS IT IS LIKE A WEASEL
Racket
<lang Racket>
- lang racket
(define alphabet " ABCDEFGHIJKLMNOPQRSTUVWXYZ") (define (randch) (string-ref alphabet (random 27)))
(define (fitness s1 s2)
(for/sum ([c1 (in-string s1)] [c2 (in-string s2)]) (if (eq? c1 c2) 1 0)))
(define (mutate s P)
(define r (string-copy s)) (for ([i (in-range (string-length r))] #:when (<= (random) P)) (string-set! r i (randch))) r)
(define (evolution target C P)
(let loop ([parent (mutate target 1.0)] [n 0])
;; (printf "~a: ~a\n" n parent)
(if (equal? parent target)
n
(let cloop ([children (for/list ([i (in-range C)]) (mutate parent P))]
[best #f] [fit -1])
(if (null? children)
(loop best (add1 n))
(let ([f (fitness target (car children))])
(if (> f fit)
(cloop (cdr children) (car children) f)
(cloop (cdr children) best fit))))))))
- Some random experiment using all of this
(define (try-run C P)
(define ns
(for/list ([i 10])
(evolution "METHINKS IT IS LIKE A WEASEL" C P)))
(printf "~s Average generation: ~s\n" C (/ (apply + 0.0 ns) (length ns)))
(printf "~s Total strings: ~s\n" C (for/sum ([n ns]) (* n 50))))
(for ([C (in-range 10 501 10)]) (try-run C 0.001)) </lang>
Raku
(formerly Perl 6)
<lang perl6>constant target = "METHINKS IT IS LIKE A WEASEL"; constant mutate_chance = .08; constant @alphabet = flat 'A'..'Z',' '; constant C = 100;
sub mutate { [~] (rand < mutate_chance ?? @alphabet.pick !! $_ for $^string.comb) } sub fitness { [+] $^string.comb Zeq target.comb }
loop (
my $parent = @alphabet.roll(target.chars).join; $parent ne target; $parent = max :by(&fitness), mutate($parent) xx C
) { printf "%6d: '%s'\n", $++, $parent }</lang>
Red
<lang Red>Red[]
- allowed characters
alphabet: "ABCDEFGHIJKLMNOPQRSTUVWXYZ "
- target string
target: "METHINKS IT IS LIKE A WEASEL"
- parameter controlling the number of children
C: 10
- parameter controlling the evolution rate
RATE: 0.05
- compute closeness of 'string' to 'target'
fitness: function [string] [
sum: 0
repeat i length? string [
if not-equal? pick string i pick target i [
sum: sum + 1
]
]
sum
]
- return copy of 'string' with mutations, frequency based on given 'rate'
mutate: function [string rate] [
result: copy string
repeat i length? result [
if rate > random 1.0 [
poke result i random/only alphabet
]
]
result
]
- create initial random parent
parent: "" repeat i length? target [
append parent random/only alphabet
]
- main loop, displaying progress
while [not-equal? parent target] [
print parent children: copy []
repeat i C [ append children mutate parent RATE ] sort/compare children function [a b] [lesser? fitness a fitness b]
parent: pick children 1
] print parent </lang>
REXX
optimized
This REXX version:
- allows random seed for repeatability of runs
- allows mutation rate to be expressed as a percentage (%)
- echoes specification(s) and target string
- columnar alignment of output
- optimized for speed (only one random number/mutation)
- supports an alphabet with lowercase letters and other letters and/or punctuation.
<lang rexx>/*REXX program demonstrates an evolutionary algorithm (by using mutation). */ parse arg children MR seed . /*get optional arguments from the C.L. */ if children== | children=="," then children=10 /*# children produced each generation. */ if MR == | MR =="," then MR= "4%" /*the character Mutation Rate each gen.*/ if right(MR,1)=='%' then MR= strip(MR,,"%")/100 /*expressed as a percent? Then adjust.*/ if seed\== then call random ,,seed /*SEED allow the runs to be repeatable.*/ abc = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ ' ; Labc= length(abc) target= 'METHINKS IT IS LIKE A WEASEL' ; Ltar= length(target) parent= mutate( left(, Ltar), 1) /*gen rand string,same length as target*/ say center('target string', Ltar, "─") 'children' "mutationRate" say target center(children, 8) center((MR*100/1)'%', 12); say say center('new string' ,Ltar, "─") "closeness" 'generation'
do gen=0 until parent==target; close= fitness(parent)
almost= parent
do children; child= mutate(parent,MR)
_= fitness(child); if _<=close then iterate
close= _; almost= child
say almost right(close, 9) right(gen, 10)
end /*children*/
parent= almost
end /*gen*/
exit /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ fitness: parse arg x; $=0; do k=1 for Ltar; $= $+(substr(x,k,1)==substr(target,k,1)); end
return $
/*──────────────────────────────────────────────────────────────────────────────────────*/ mutate: parse arg x,rate; $= /*set X to 1st argument, RATE to 2nd.*/
do j=1 for Ltar; r= random(1, 100000) /*REXX's max for RANDOM*/
if .00001*r<=rate then $= $ || substr(abc, r//Labc+1, 1)
else $= $ || substr(x , j , 1)
end /*j*/
return $</lang>
- output when using the following input: 20 4% 11
───────target string──────── children mutationRate METHINKS IT IS LIKE A WEASEL 20 4% ─────────new string───────── closeness generation TWLPLGNVVMXFBUKHUPEQXOCUPIUS 1 0 TWLPLGNVVMXFBU HUPEQXOCUPIUS 2 1 TWLPLGNVVMX BU HUPEQXOCUPIUS 3 2 TWLPLCNVFMX BP HUPEQAOCUPIUS 4 4 TWLPLQNVFMX BP HUPEQAOCUPGUL 5 6 TWLHLQNVFMX BS HUPEQAOUUPGUL 7 9 RWLHLQNZFMX BS HUPEQAOUUEGEL 8 14 RWLHLQNZFIX BS HUPEQAOUUEGEL 9 15 RWLHLQNZFIX BS HUPE AOUUEGEL 10 19 RWLHLQNZFIX BS LWPE AOUUEGEL 11 22 RWLHLQNZFIX BS LWPE A UUEGEL 12 28 RWLHLNNZFIX BS LWPE A UUEGEL 13 36 RELHLNNZFIX BE LWPE A UUAGEL 14 40 RELHLNNZFIX BE LWPE A UUASEL 15 43 RELHLNNZFIX BE LWKE A UASEL 16 50 RELHLNNZFIT BE LWKE A UASEL 17 62 RELHLNNSFIT IE LWKE A UASEL 19 67 RETHLNNSFIT IE LWKE A UASEL 20 71 RETHLNNSFIT IE LIKE A UASEL 21 79 METHLNNSFIT IE LIKE A LASEL 22 91 METHLNNSFIT IE LIKE A WLASEL 23 112 METHLNNSFIT IE LIKE A WEASEL 24 144 METHLNNS IT IE LIKE A WEASEL 25 151 METHLNKS IT IM LIKE A WEASEL 26 160 METHLNKS IT IS LIKE A WEASEL 27 164 METHINKS IT IS LIKE A WEASEL 28 170
optimized, stemmed arrays
This REXX version uses stemmed arrays for the character-by-character comparison [T.n] as well as
generating a random character [@.n] during mutation, thus making it slightly faster (about 10%),
especially for a longer string and/or a low mutation rate.
<lang rexx>/*REXX program demonstrates an evolutionary algorithm (by using mutation). */
parse arg children MR seed . /*get optional arguments from the C.L. */
if children== | children=="," then children=10 /*# children produced each generation. */
if MR == | MR =="," then MR= "4%" /*the character Mutation Rate each gen.*/
if right(MR,1)=='%' then MR= strip(MR,,"%")/100 /*expressed as a percent? Then adjust.*/
if seed\== then call random ,,seed /*SEED allow the runs to be repeatable.*/
abc = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ '; Labc= length(abc)
do i=0 for Labc; @.i= substr(abc, i+1, 1) /*define array (for faster compare), */ end /*i*/ /*than picking one from a char string. */
target= 'METHINKS IT IS LIKE A WEASEL' ; Ltar= length(target)
do j=1 for Ltar; T.j= substr(target, j, 1) /*define an array (for faster compare),*/ end /*j*/ /*faster than a byte-by-byte compare. */
parent= mutate( left(, Ltar), 1) /*gen rand string, same length as tar. */ say center('target string', Ltar, "─") 'children' "mutationRate" say target center(children, 8) center( (MR*100/1)'%', 12); say say center('new string' , Ltar, "─") 'closeness' "generation"
do gen=0 until parent==target; close= fitness(parent)
almost= parent
do children; child= mutate(parent, MR)
_= fitness(child); if _<=close then iterate
close= _; almost= child
say almost right(close, 9) right(gen, 10)
end /*children*/
parent= almost
end /*gen*/
exit /*stick a fork in it, we're all done. */ /*──────────────────────────────────────────────────────────────────────────────────────*/ fitness: parse arg x; $=0; do k=1 for Ltar; $=$+(substr(x,k,1)==T.k); end; return $ /*──────────────────────────────────────────────────────────────────────────────────────*/ mutate: parse arg x,rate /*set X to 1st argument, RATE to 2nd.*/
$=; do m=1 for Ltar; r=random(1, 100000) /*REXX's max for RANDOM*/
if .00001*r<=rate then do; _= r//Labc; $= $ || @._; end
else $= $ || substr(x, m, 1)
end /*m*/
return $</lang>
- output is the same as the previous version.
Ring
<lang ring>
- Project : Evolutionary algorithm
target = "METHINKS IT IS LIKE A WEASEL" parent = "IU RFSGJABGOLYWF XSMFXNIABKT" num = 0 mutationrate = 0.5 children = len(target) child = list(children) while parent != target
bestfitness = 0
bestindex = 0
for index = 1 to children
child[index] = mutate(parent, mutationrate)
fitness = fitness(target, child[index])
if fitness > bestfitness
bestfitness = fitness
bestindex = index
ok
next
if bestindex > 0
parent = child[bestindex]
num = num + 1
see "" + num + ": " + parent + nl
ok
end
func fitness(text, ref)
f = 0
for i = 1 to len(text)
if substr(text, i, 1) = substr(ref, i, 1)
f = f + 1
ok
next
return (f / len(text))
func mutate(text, rate)
rnd = randomf()
if rate > rnd
c = 63+random(27)
if c = 64
c = 32
ok
rnd2 = random(len(text))
if rnd2 > 0
text[rnd2] = char(c)
ok
ok
return text
func randomf()
decimals(10)
str = "0."
for i = 1 to 10
nr = random(9)
str = str + string(nr)
next
return number(str)
</lang> Output:
1: IU RFPGJABGOLYWF XSMFXNIABKT 2: IU RFPGJABGOLQWF XSMFXNIABKT 3: IU RFPGJABGOLQWF XSMAXNIABKT 4: IU RFPGJABGOLQWF XSMA NIABKT 5: IU RFPGJABGOLQWF XSMA NIABKT 6: IU RFPGJABGOLSWF XSMA NIABKT 7: IU RFPGJABGOLSWF XSMA NIABKT 8: IUTRFPGJABGOLSWF XSMA NIABKT 9: IUTRFPGSABGOLSWF XSMA NIABKT 10: IUTRFPGSABGOLSWF XSMA NIABKT 11: IUTRFPGSABGOLSWF XSMA NIABKT 12: IUTRFPGSABGOLSWF XSMA NIABKT 13: IUTRFPGSABGOLSWF XSMA NIABKE 14: IUTRFPGSABGOMSWF XSMA NIABKE 15: IUTRFPGSYBGOMSWF XSMA NIABKE 16: IUTRFPGSYBGOMSWF XSMA NIABKE 17: IUTRFPGSYBGOMSWF XSMA NIABKE 18: IUTRFPGSYBGOMSWF XSMA NIASKE 19: IUTRFPGSYBGOMSWF XSMA NIASKE 20: IUTRFPGSYMGOMSWF XSMA NIASKE 21: IUTRFPGSYMGOMSWF XSMA NIASKE 22: IUTRFPGSYMGOMSWF XSMA NEASKE 23: IUTRFPGSYMGOMSWF XSMA NEASKE 24: IUTRFPGSYMG MSWF XSMA NEASKE 25: IUTRFPGSYMG MSWF XSMA NEASKE 26: MUTRFPGSYMG MSWF XSMA NEASKE 27: MUTRFPGSYMX MSWF XSMA NEASKE 28: MUTRFPGSYMX MSWFIXSMA NEASKE 29: MUTRFPGSYMX MSWFIXSMA NEASKE 30: MUTRFPGSYIX MSWFIXSMA NEASKE 31: MUTRFPGSYIX MSWLIXSMA NEASKE 32: MUTRFPGSYIX MSWLIXSMA NEASKE 33: MUTRFPGSYIX MSWLIXSMA NEASKL 34: MUTRFPGSYIX MSWLIXSMA NEASKL 35: MUTRFPGSYIX MSKLIXSMA NEASKL 36: MUTRFPKSYIX MSKLIXSMA NEASKL 37: MUTRFPKSYIX MSKLIXSMA NEASKL 38: MUTRFPKSYIX MS LIXSMA NEASKL 39: MUTRFPKSYIX MS LIXSMA NEASEL 40: MUTRFPKSYIX MS LIXYMA NEASEL 41: MUTRFPKS IX MS LIXYMA NEASEL 42: MUTRFPKS IX MS LIXYMA NEASEL 43: MUTRFPKS IX MS LIXYMA WEASEL 44: MUTRFPKS IX MS LIXYMA WEASEL 45: MUTRFPKS IX MS LIXYMA WEASEL 46: MUTRFPKS IJ MS LIXYMA WEASEL 47: MUTRFPKS IJ MS LIXYMA WEASEL 48: MUTRFPKS IJ MS LIXYMA WEASEL 49: MUTRFPKS IJ MS LIXYMA WEASEL 50: MUTRFPKS IJ MS LIXYMA WEASEL 51: MUTRFPKS IJ MS LIXYMA WEASEL 52: MUTRIPKS IJ MS LIXYMA WEASEL 53: MUTRIPKS IJ MS LIXYMA WEASEL 54: MUTRIPKS IJ MS LIXYMA WEASEL 55: MUTRIPKS IJ MS LIXYMA WEASEL 56: MUTRIPKS IJ MS LIKYMA WEASEL 57: MUTRIPKS IJ MS LIKYMA WEASEL 58: MUTRIPKS IJ MS LIKYMA WEASEL 59: MUTRIPKS IJ MS LIKYMA WEASEL 60: MUTRIPKS IJ MS LIKY A WEASEL 61: MUTRIPKS IJ MS LIKY A WEASEL 62: MUTRIPKS IJ MS LIKY A WEASEL 63: MUTRIPKS IT MS LIKY A WEASEL 64: MUTRIPKS IT MS LIKY A WEASEL 65: MUTRIPKS IT MS LIKY A WEASEL 66: MUTRIPKS IT MS LIKY A WEASEL 67: MUTRIPKS IT MS LIKE A WEASEL 68: MUTRIPKS IT MS LIKE A WEASEL 69: MUTRIPKS IT MS LIKE A WEASEL 70: MUTRIPKS IT MS LIKE A WEASEL 71: MUTVIPKS IT MS LIKE A WEASEL 72: MUTVIPKS IT MS LIKE A WEASEL 73: MUTVIPKS IT MS LIKE A WEASEL 74: MUTVIPKS IT MS LIKE A WEASEL 75: MUTVIPKS IT MS LIKE A WEASEL 76: MUTVIPKS IT MS LIKE A WEASEL 77: MUTVIPKS IT MS LIKE A WEASEL 78: METVIPKS IT MS LIKE A WEASEL 79: METVIPKS IT MS LIKE A WEASEL 80: METVIPKS IT RS LIKE A WEASEL 81: METVIPKS IT RS LIKE A WEASEL 82: METVIPKS IT RS LIKE A WEASEL 83: METFIPKS IT RS LIKE A WEASEL 84: METFIPKS IT RS LIKE A WEASEL 85: METFIPKS IT RS LIKE A WEASEL 86: METFIPKS IT RS LIKE A WEASEL 87: METFIPKS IT RS LIKE A WEASEL 88: METFIPKS IT RS LIKE A WEASEL 89: METHIPKS IT RS LIKE A WEASEL 90: METHINKS IT RS LIKE A WEASEL 91: METHINKS IT ?S LIKE A WEASEL 92: METHINKS IT ?S LIKE A WEASEL 93: METHINKS IT ?S LIKE A WEASEL 94: METHINKS IT ?S LIKE A WEASEL 95: METHINKS IT ?S LIKE A WEASEL 96: METHINKS IT ?S LIKE A WEASEL 97: METHINKS IT ?S LIKE A WEASEL 98: METHINKS IT ?S LIKE A WEASEL 99: METHINKS IT ?S LIKE A WEASEL 100: METHINKS IT ?S LIKE A WEASEL 101: METHINKS IT ?S LIKE A WEASEL 102: METHINKS IT ?S LIKE A WEASEL 103: METHINKS IT ?S LIKE A WEASEL 104: METHINKS IT ?S LIKE A WEASEL 105: METHINKS IT ?S LIKE A WEASEL 106: METHINKS IT ?S LIKE A WEASEL 107: METHINKS IT ?S LIKE A WEASEL 108: METHINKS IT ?S LIKE A WEASEL 109: METHINKS IT ?S LIKE A WEASEL 110: METHINKS IT ?S LIKE A WEASEL 111: METHINKS IT ?S LIKE A WEASEL 112: METHINKS IT ?S LIKE A WEASEL 113: METHINKS IT ?S LIKE A WEASEL 114: METHINKS IT ?S LIKE A WEASEL 115: METHINKS IT ?S LIKE A WEASEL 116: METHINKS IT ?S LIKE A WEASEL 117: METHINKS IT ?S LIKE A WEASEL 118: METHINKS IT ?S LIKE A WEASEL 119: METHINKS IT ?S LIKE A WEASEL 120: METHINKS IT ?S LIKE A WEASEL 121: METHINKS IT ?S LIKE A WEASEL 122: METHINKS IT ?S LIKE A WEASEL 123: METHINKS IT ?S LIKE A WEASEL 124: METHINKS IT ?S LIKE A WEASEL 125: METHINKS IT ?S LIKE A WEASEL 126: METHINKS IT ?S LIKE A WEASEL 127: METHINKS IT ?S LIKE A WEASEL 128: METHINKS IT IS LIKE A WEASEL
Ruby
for the sample method.
<lang ruby>@target = "METHINKS IT IS LIKE A WEASEL" Charset = [" ", *"A".."Z"] COPIES = 100
def random_char; Charset.sample end
def fitness(candidate)
sum = 0
candidate.chars.zip(@target.chars) {|x,y| sum += (x[0].ord - y[0].ord).abs}
100.0 * Math.exp(Float(sum) / -10.0)
end
def mutation_rate(candidate)
1.0 - Math.exp( -(100.0 - fitness(candidate)) / 400.0)
end
def mutate(parent, rate)
parent.each_char.collect {|ch| rand <= rate ? random_char : ch}.join
end
def log(iteration, rate, parent)
puts "%4d %.2f %5.1f %s" % [iteration, rate, fitness(parent), parent]
end
iteration = 0 parent = Array.new(@target.length) {random_char}.join prev = ""
while parent != @target
iteration += 1
rate = mutation_rate(parent)
if prev != parent
log(iteration, rate, parent)
prev = parent
end
copies = [parent] + Array.new(COPIES) {mutate(parent, rate)}
parent = copies.max_by {|c| fitness(c)}
end log(iteration, rate, parent)</lang>
- Output:
1 0.22 0.0 FBNLRACAYQJAAJRNKNGZJMBQWBBW 2 0.22 0.0 QBNLGHPAYQJALJZGZNGAJMVQLBBW 3 0.22 0.0 JBNLGDPA QJALJZOZNGGTMVKLTBV 4 0.22 0.0 NSNLGDPA QTAMJ OZNVGTMVHOTBV 5 0.22 0.0 NSNLGVPA QTAMR OZVVGT VHOTBV 6 0.22 0.0 NSWLGVPA QTAMR OZVHGD VHOTBV 7 0.22 0.0 NSWLGVPA QTALR OGJHGD VHOTBV 8 0.22 0.0 NSWLGNPA QTALR OGJHGE VHNTBV 9 0.22 0.0 NSWWGMPY QT LR OJAHGE VHNTBV 10 0.22 0.0 NSWWGMPW QT LR OJAH E VJNTXV 11 0.22 0.0 JSZWGMPW QT LR OQAH E VJNWLF 12 0.22 0.0 JJZGJMPW QT LR OIAH E VJNWLF 13 0.22 0.0 IJZGJMPW DT HR OIHH E VJNWLF 14 0.22 0.1 NJZGJMPW DT HR OIHH E VCEZLF 17 0.22 0.2 NJZGJMPW KT HR OIHH E VCEPLF 22 0.22 0.2 NDZGJMPQ KW HR OIHH E VCEPLF 25 0.22 0.3 NDZGJMPQ KW HR LIHH E VCEPOO 26 0.22 0.5 NDZGJQJQ JS HR LIHH E VCEPOO 28 0.22 0.6 NDZGJQJQ IS HR LIHH E VCEPOO 29 0.22 0.6 NDZGJLJQ IS HR LIHH E VCEPOO 30 0.22 0.7 NDZGJLJQ IS ER LIHH E VCEPKO 35 0.22 0.8 NDZGJLJQ IS KR LIHH E VCEPKO 40 0.22 1.5 NDZGJLJQ IS KR LINH D VCEPFO 46 0.22 1.7 NDZGJLJQ IS KR LIMH D VCEPFO 47 0.21 3.3 NDZGJLJQ IS KR LILB D VCAPFM 66 0.21 3.7 NDSGJLJQ IS KR LIGI D VCAPFM 67 0.21 4.5 NDSGJLJQ IS IR LIGI D VCAPFM 70 0.21 6.1 NDTGJLMQ IS IS LIGI D VCATFM 72 0.21 6.7 NDTGJLMQ IS IS LIHI D VCATFM 77 0.21 8.2 NDTGJLMQ IU IS LIHI B VCATFM 83 0.20 9.1 NDTGJLLQ IU IS LIHI B VCATFM 87 0.20 10.0 NDTGJLLQ IU IS LIHH B VCATFM 108 0.20 11.1 NDTGJLLT IU IS LIHH B VCATFM 118 0.19 13.5 NDTGJNLT IU IS LIHH B VCATFM 128 0.18 18.3 MDTGJNLT IU IS LILH B VCATFM 153 0.18 20.2 NDTGJNLT IU IS LILH B VEATFM 155 0.17 24.7 NDTGJNLT IU IS LILE B VDATFM 192 0.17 27.3 NDTGJNLS IU IS LILE B VDATFM 225 0.16 30.1 NDTGJNLS IU IS LILE B VDASFM 226 0.15 33.3 NDTGJNLS IU IS LILE B VDASFL 227 0.15 36.8 NDTGJNLS IT IS LILE B VDASFL 246 0.14 40.7 NDTGJNKS IT IS LILE B VDASFL 252 0.13 44.9 NETGJNKS IT IS LILE B VDASFL 256 0.12 49.7 NETGJNKS IT IS LILE B WDASFL 260 0.11 54.9 NETGINKS IT IS LILE B WDASDL 284 0.09 60.7 NETHINKS IT IS LILE B WDASDL 300 0.08 67.0 NETHINKS IT IS LIKE B WDASDL 309 0.06 74.1 NETHINKS IT IS LIKE B WDASEL 311 0.04 81.9 NETHINKS IT IS LIKE A WDASEL 316 0.02 90.5 METHINKS IT IS LIKE A WDASEL 335 0.02 100.0 METHINKS IT IS LIKE A WEASEL
Rust
<lang Rust>//! Author : Thibault Barbie //! //! A simple evolutionary algorithm written in Rust.
extern crate rand;
use rand::Rng;
fn main() {
let target = "METHINKS IT IS LIKE A WEASEL"; let copies = 100; let mutation_rate = 20; // 1/20 = 0.05 = 5%
let mut rng = rand::weak_rng();
// Generate first sentence, mutating each character let start = mutate(&mut rng, target, 1); // 1/1 = 1 = 100%
println!("{}", target);
println!("{}", start);
evolve(&mut rng, target, start, copies, mutation_rate);
}
/// Evolution algorithm /// /// Evolves `parent` to match `target`. Returns the number of evolutions performed. fn evolve<R: Rng>(
rng: &mut R, target: &str, mut parent: String, copies: usize, mutation_rate: u32,
) -> usize {
let mut counter = 0; let mut parent_fitness = target.len() + 1;
loop {
counter += 1;
let (best_fitness, best_sentence) = (0..copies)
.map(|_| {
// Copy and mutate a new sentence.
let sentence = mutate(rng, &parent, mutation_rate);
// Find the fitness of the new mutation
(fitness(target, &sentence), sentence)
})
.min_by_key(|&(f, _)| f) // find the closest mutation to the target
.unwrap(); // fails if `copies == 0`
// If the best mutation of this generation is better than `parent` then "the fittest
// survives" and the next parent becomes the best of this generation.
if best_fitness < parent_fitness {
parent = best_sentence;
parent_fitness = best_fitness;
println!(
"{} : generation {} with fitness {}",
parent, counter, best_fitness
);
if best_fitness == 0 {
return counter;
}
}
}
}
/// Computes the fitness of a sentence against a target string, returning the number of /// incorrect characters. fn fitness(target: &str, sentence: &str) -> usize {
sentence
.chars()
.zip(target.chars())
.filter(|&(c1, c2)| c1 != c2)
.count()
}
/// Mutation algorithm. /// /// It mutates each character of a string, according to a `mutation_rate`. fn mutate<R: Rng>(rng: &mut R, sentence: &str, mutation_rate: u32) -> String {
let maybe_mutate = |c| {
if rng.gen_weighted_bool(mutation_rate) {
random_char(rng)
} else {
c
}
};
sentence.chars().map(maybe_mutate).collect()
}
/// Generates a random letter or space. fn random_char<R: Rng>(rng: &mut R) -> char {
// Returns a value in the range [A, Z] + an extra slot for the space character. (The `u8`
// values could be cast to larger integers for a better chance of the RNG hitting the proper
// range).
match rng.gen_range(b'A', b'Z' + 2) {
c if c == b'Z' + 1 => ' ', // the `char` after 'Z'
c => c as char,
}
}</lang>
- Output:
METHINKS IT IS LIKE A WEASEL ZPNUDZUKIHR SRD SZNRWOZDAXJX ZPNUDZKKIHR SRD SZNJWOZDAXJX : generation 1 with fitness 25 ZPHUDZKKIHR SRD SZNJWOWDAXJX : generation 2 with fitness 24 ZPGUDZKSIHR SRD SZNJWOWDAXJX : generation 3 with fitness 23 ZPGUDZKSIIR SRD SUNJWOWXAXJX : generation 4 with fitness 22 ZEGUDZKSIIR SRD SUNJWOWXAXJX : generation 5 with fitness 21 ZECUDZKSIIR SRD SUN WOWEAXJX : generation 6 with fitness 19 ZECUDZKSIIN SRD SUN AOWEAXJX : generation 7 with fitness 18 ZECUDSKSIIN IRD SUN AOWEAXJX : generation 8 with fitness 17 ZECUDSKSIIN IRDLSUN AOWEAXJX : generation 9 with fitness 16 ZETUDSKSIIN IRDLSUN AOWEAXJX : generation 10 with fitness 15 ZETUDSKSIIN IRDLSUN A WEAXJX : generation 11 with fitness 14 ZETUDSKSIIT IRDLSUN A WEAXJX : generation 12 with fitness 13 ZETUDSKSIIT IRDLSUN A WEAXER : generation 13 with fitness 12 ZETHDSKSIIT IRDLSUN A WEAXER : generation 14 with fitness 11 ZETHDSKSIIT IRDLSKN A WEAXER : generation 15 with fitness 10 ZETHDSKSIIT IRDLIKN A WEAXER : generation 17 with fitness 9 ZETHDSKSIIT IR LIKN A WEAXER : generation 19 with fitness 8 ZETHDSKS IT IR LIKN A WEAXER : generation 23 with fitness 7 ZETHDSKS IT IR LIKN A WEASER : generation 26 with fitness 6 ZETHDOKS IT IR LIKE A WEASER : generation 28 with fitness 5 ZETHDNKS IT IR LIKE A WEASER : generation 31 with fitness 4 ZETHCNKS IT IR LIKE A WEASEL : generation 45 with fitness 3 ZETHCNKS IT IS LIKE A WEASEL : generation 46 with fitness 2 METHCNKS IT IS LIKE A WEASEL : generation 68 with fitness 1 METHINKS IT IS LIKE A WEASEL : generation 79 with fitness 0
Scala
<lang scala>import scala.annotation.tailrec
case class LearnerParams(target:String,rate:Double,C:Int)
val chars = ('A' to 'Z') ++ List(' ') val randgen = new scala.util.Random def randchar = {
val charnum = randgen.nextInt(chars.size) chars(charnum)
}
class RichTraversable[T](t: Traversable[T]) {
def maxBy[B](fn: T => B)(implicit ord: Ordering[B]) = t.max(ord on fn) def minBy[B](fn: T => B)(implicit ord: Ordering[B]) = t.min(ord on fn)
}
implicit def toRichTraversable[T](t: Traversable[T]) = new RichTraversable(t)
def fitness(candidate:String)(implicit params:LearnerParams) =
(candidate zip params.target).map { case (a,b) => if (a==b) 1 else 0 }.sum
def mutate(initial:String)(implicit params:LearnerParams) =
initial.map{ samechar => if(randgen.nextDouble < params.rate) randchar else samechar }
@tailrec def evolve(generation:Int, initial:String)(implicit params:LearnerParams){
import params._
printf("Generation: %3d %s\n",generation, initial)
if(initial == target) return ()
val candidates = for (number <- 1 to C) yield mutate(initial)
val next = candidates.maxBy(fitness)
evolve(generation+1,next)
}
implicit val params = LearnerParams("METHINKS IT IS LIKE A WEASEL",0.01,100) val initial = (1 to params.target.size) map(x => randchar) mkString evolve(0,initial)</lang>
Scheme
<lang scheme> (import (scheme base)
(scheme write)
(srfi 27)) ; random numbers
(random-source-randomize! default-random-source)
(define target "METHINKS IT IS LIKE A WEASEL") ; target string (define C 100) ; size of population (define p 0.1) ; chance any char is mutated
- return a random character in given range
(define (random-char)
(string-ref "ABCDEFGHIJKLMNOPQRSTUVWXYZ "
(random-integer 27)))
- compute distance of given string from target
(define (fitness str)
(apply +
(map (lambda (c1 c2) (if (char=? c1 c2) 0 1))
(string->list str)
(string->list target))))
- mutate given parent string, returning a new string
(define (mutate str)
(string-map (lambda (c)
(if (< (random-real) p)
(random-char)
c))
str))
- create a population by mutating parent,
- returning a list of variations
(define (make-population parent)
(do ((pop '() (cons (mutate parent) pop))) ((= C (length pop)) pop)))
- find the most fit candidate in given list
(define (find-best candidates)
(define (select-best a b)
(if (< (fitness a) (fitness b)) a b))
;
(do ((best (car candidates) (select-best best (car rem)))
(rem (cdr candidates) (cdr rem)))
((null? rem) best)))
- create first parent from random characters
- of same size as target string
(define (initial-parent)
(do ((res '() (cons (random-char) res)))
((= (length res) (string-length target))
(list->string res))))
- run the search
(do ((parent (initial-parent) (find-best (cons parent (make-population parent))))) ; select best from parent and population
((string=? parent target) (display (string-append "Found: " parent "\n"))) (display parent) (newline))
</lang>
Seed7
<lang seed7>$ include "seed7_05.s7i";
const string: table is "ABCDEFGHIJKLMNOPQRSTUVWXYZ ";
const func integer: unfitness (in string: a, in string: b) is func
result
var integer: sum is 0;
local
var integer: index is 0;
begin
for index range 1 to length(a) do
sum +:= ord(a[index] <> b[index]);
end for;
end func;
const proc: mutate (in string: a, inout string: b) is func
local
var integer: index is 0;
begin
b := a;
for index range 1 to length(a) do
if rand(1, 15) = 1 then
b @:= [index] table[rand(1, 27)];
end if;
end for;
end func;
const proc: main is func
local
const string: target is "METHINKS IT IS LIKE A WEASEL";
const integer: OFFSPRING is 30;
var integer: index is 0;
var integer: unfit is 0;
var integer: best is 0;
var integer: bestIndex is 0;
var integer: generation is 1;
var string: parent is " " mult length(target);
var array string: children is OFFSPRING times " " mult length(target);
begin
for index range 1 to length(target) do
parent @:= [index] table[rand(1, 27)];
end for;
repeat
for index range 1 to OFFSPRING do
mutate(parent, children[index]);
end for;
best := succ(length(parent));
bestIndex := 0;
for index range 1 to OFFSPRING do
unfit := unfitness(target, children[index]);
if unfit < best then
best := unfit;
bestIndex := index;
end if;
end for;
if bestIndex <> 0 then
parent := children[bestIndex];
end if;
writeln("generation " <& generation <& ": score " <& best <& ": " <& parent);
incr(generation);
until best = 0;
end func;</lang>
SequenceL
SequenceL Code:
<lang sequencel>import <Utilities/Sequence.sl>;
AllowedChars := " ABCDEFGHIJKLMNOPQRSTUVWXYZ";
initializeParent(randChars(1)) := AllowedChars[randChars];
Fitness(target(1), current(1)) := let fit[i] := true when target[i] = current[i]; in size(fit);
Mutate(letter(0), rate(0), randRate(0), randChar(0)) := letter when randRate > rate else AllowedChars[randChar];
evolve(target(1), parent(1), C(0), P(0), rateRands(2), charRands(2)) := let mutations[i] := Mutate(parent, P, rateRands[i], charRands[i]) foreach i within 1 ... C; fitnesses := Fitness(target, mutations); in mutations[firstIndexOf(fitnesses, vectorMax(fitnesses))];</lang>
C++ Driver Code:
<lang cpp>#include <iostream>
- include <time.h>
- include "SL_Generated.h"
using namespace std;
int main(int argc, char** argv) { int threads = 0;
char* targetString = "METHINKS IT IS LIKE A WEASEL"; if(argc > 1) targetString = argv[1]; int C = 100; if(argc > 2) C = atoi(argv[2]); SL_FLOAT P = 0.05; if(argc > 3) P = atof(argv[3]); int seed = time(NULL); if(argc > 4) seed = atoi(argv[4]);
int targetDims[] = {strlen(targetString), 0}; Sequence<char> target((void*)targetString, targetDims);
sl_init(threads);
Sequence<char> parent; Sequence<char> newParent; Sequence<int> parentRands; sl_create(seed++, 1, 27, target.size(), threads, parentRands); sl_initializeParent(parentRands, threads, parent);
Sequence< Sequence<int> > charRands; Sequence< Sequence<SL_FLOAT> > rateRands;
cout << "Start:\t" << parent << endl; for(int i = 1; !(parent == target); i++) { sl_create(seed++, 1, 27, C, target.size(), threads, charRands); sl_create(seed++, 0.0, 1.0, C, target.size(), threads, rateRands);
sl_evolve(target, parent, C, P, rateRands, charRands, threads, newParent); parent = newParent;
cout << "#" << i << ":\t" << parent << endl; } cout << "End:\t" << parent << endl;
sl_done();
return 0; }</lang>
- Output:
Start: "EDVSWRXSQWK VWUOGAWSTRJWY EW" #1: "EDVSWRXSQIK VWUOGAWSTRJWY EW" #2: "EDVSWRXSQIK VWUOGAESTRJWY EW" #3: "EDVSWRXSQIK VWUOGAESTRJWY EL" #4: "MDVSWRHSQIK VWUOGAESTRJWY EL" #5: "MDVSWRHSQIK VW OGAESTRJWY EL" #6: "MDVSWRHSQIK IW OGAESTRJOY EL" #7: "MDVSWRHSQIK IW OGAESTRWOY EL" #8: "MDVSWRHSQIK IW OGAESARWOY EL" #9: "MDVSWRHSQIK IW OGAESARWOY EL" #10: "MDVSWRHSQIK IW OGAESARWOY EL" #11: "MDVSWRHSQIK IW OGAESARWOY EL" #12: "MDVSWRHSQIK IW LGAESANWOY EL" #13: "MDVSWJHSXIK IW LGAESANWOY EL" #14: "MEVSWJHSXIK IW LGAESANWOY EL" #15: "MEVSWJHSXIK IA LVAESANWOY EL" #16: "MEVSWJHSXIK IA LVAESACWOY EL" #17: "MEVSWRHSXIK IA LVAESACWOADEL" #18: "MEVIWRHSXIK IA LVAESACWOADEL" #19: "MENIWRHSXIK IA LVAE ACWOADEL" #20: "MENIWRHSXIK IA LVAE ACWOADEL" #21: "MENIWRHS IK IA LVAE ACWOADEL" #22: "MENIWRHS IK IA LVAE A WOADEL" #23: "METIKRAS IK IA LCAE A WOADEL" #24: "METIKRAS IK IA LCIE A WOADEL" #25: "METIKRAS IK IA LCIE A WOASEL" #26: "METIKRAS IK IA LCIE A WOASEL" #27: "METIKRAS IK IA LCIE A WEASEL" #28: "METIKRKS IK IA LCIE A WEASEL" #29: "METIKRKS IK IA LCIE A WEASEL" #30: "METIKRKS IK IA LCIE A WEASEL" #31: "METIKRKS IK IU LOIE A WEASEL" #32: "METIKRKS IT IU LOIE A WEASEL" #33: "METIKRKS IT IU LOIE A WEASEL" #34: "METIKRKS IT IU LIIE A WEASEL" #35: "METIKRKS IT IU LIIE A WEASEL" #36: "METHKRKS IT IU LIIE A WEASEL" #37: "METHKRKS IT IU LIIE A WEASEL" #38: "METHKRKS IT IU LIIE A WEASEL" #39: "METHCRKS IT IU LIIE A WEASEL" #40: "METHCRKS IT IU LIIE A WEASEL" #41: "METHCRKS IT IU LIIE A WEASEL" #42: "METHCRKS IT IU LIIE A WEASEL" #43: "METHCRKS IT IU LIIE A WEASEL" #44: "METHCRKS IT IU LIIE A WEASEL" #45: "METHCRKS IT IU LIIE A WEASEL" #46: "METHZRKS IT IU LIKE A WEASEL" #47: "METHZRKS IT IU LIKE A WEASEL" #48: "METHZRKS IT IU LIKE A WEASEL" #49: "METHZRKS IT IU LIKE A WEASEL" #50: "METHGRKS IT IU LIKE A WEASEL" #51: "METHGRKS IT IL LIKE A WEASEL" #52: "METHGYKS IT IL LIKE A WEASEL" #53: "METHGYKS IT IL LIKE A WEASEL" #54: "METHIYKS IT IL LIKE A WEASEL" #55: "METHIYKS IT IS LIKE A WEASEL" #56: "METHIYKS IT IS LIKE A WEASEL" #57: "METHIYKS IT IS LIKE A WEASEL" #58: "METHIYKS IT IS LIKE A WEASEL" #59: "METHIYKS IT IS LIKE A WEASEL" #60: "METHIYKS IT IS LIKE A WEASEL" #61: "METHIYKS IT IS LIKE A WEASEL" #62: "METHIYKS IT IS LIKE A WEASEL" #63: "METHIYKS IT IS LIKE A WEASEL" #64: "METHIYKS IT IS LIKE A WEASEL" #65: "METHIYKS IT IS LIKE A WEASEL" #66: "METHIYKS IT IS LIKE A WEASEL" #67: "METHIYKS IT IS LIKE A WEASEL" #68: "METHIYKS IT IS LIKE A WEASEL" #69: "METHIYKS IT IS LIKE A WEASEL" #70: "METHIYKS IT IS LIKE A WEASEL" #71: "METHIYKS IT IS LIKE A WEASEL" #72: "METHIYKS IT IS LIKE A WEASEL" #73: "METHIYKS IT IS LIKE A WEASEL" #74: "METHIYKS IT IS LIKE A WEASEL" #75: "METHIYKS IT IS LIKE A WEASEL" #76: "METHIYKS IT IS LIKE A WEASEL" #77: "METHINKS IT IS LIKE A WEASEL" End: "METHINKS IT IS LIKE A WEASEL"
Sidef
<lang ruby>define target = "METHINKS IT IS LIKE A WEASEL" define mutate_chance = 0.08 define alphabet = [('A'..'Z')..., ' '] define C = 100
func fitness(str) { str.chars ~Z== target.chars -> count(true) } func mutate(str) { str.gsub(/(.)/, {|s1| 1.rand < mutate_chance ? alphabet.pick : s1 }) }
for (
var (i, parent) = (0, alphabet.rand(target.len).join);
parent != target;
parent = C.of{ mutate(parent) }.max_by(fitness)
) { printf("%6d: '%s'\n", i++, parent) }</lang>
Sinclair ZX81 BASIC
Requires at least 2k of RAM. Displaying everything while it's running (generation count, parent, children, and their fitness scores) slows it down somewhat; but it would be very slow anyway, and it's nice to be able to look in on it from time to time and see how the program's getting along. <lang basic> 10 LET A$="ABCDEFGHIJKLMNOPQRSTUVWXYZ "
20 LET T$="METHINKS IT IS LIKE A WEASEL" 30 LET L=LEN T$ 40 LET C=10 50 LET M=0.05 60 LET G=0 70 DIM C$(C,L) 80 LET P$="" 90 FOR I=1 TO L
100 LET P$=P$+A$(INT (RND*LEN A$)+1) 110 NEXT I 120 PRINT AT 1,0;P$ 130 LET S$=P$ 140 GOSUB 390 150 LET N=R 160 PRINT AT 1,30;N 170 PRINT AT 0,4;G 180 IF P$=T$ THEN GOTO 440 190 FOR I=1 TO C 200 FOR J=1 TO L 210 LET C$(I,J)=P$(J) 220 IF RND<=M THEN LET C$(I,J)=A$(INT (RND*LEN A$)+1) 230 PRINT AT I+2,J-1;C$(I,J) 240 NEXT J 250 PRINT AT I+2,30;" " 260 NEXT I 270 LET F=0 280 FOR I=1 TO C 290 LET S$=C$(I) 300 GOSUB 390 310 PRINT AT I+2,30;R 320 IF R>N THEN LET F=I 330 IF R>N THEN LET N=R 340 NEXT I 350 IF F>0 THEN LET P$=C$(F) 360 LET G=G+1 370 PRINT AT 1,0;P$ 380 GOTO 160 390 LET R=0 400 FOR K=1 TO L 410 IF S$(K)=T$(K) THEN LET R=R+1 420 NEXT K 430 RETURN</lang>
- Output:
349 METHINKS IT IS LIKE A WEASEL 28 METHINKS ITCIS LIKE A WEASEL 27 METHINKS ITCIS LIKE A WEASEL 27 METHINKS ITCIS LIKECA WEASEL 26 METHINKS ITCIS LPKE AUWEASLL 24 METHINKS CTCIS LIKP A WEASEL 25 METHINKS ITCIC LIKE A WEASER 25 METHINKS I CIS LIKE A WEASEL 26 METHINKS IYCIS LIREAA WEAWEL 23 METHINKS IT IS LIKE A WEASEL 28 METHINKSIITCIS LIKE A WEASEJ 25
Smalltalk
<lang smalltalk>String subclass: Mutant [
<shape: #character>
Target := Mutant from: 'METHINKS IT IS LIKE A WEASEL'. Letters := ' ABCDEFGHIJKLMNOPQRSTUVWXYZ'.
Mutant class >> run: c rate: p
["Run Evolutionary algorighm, using c copies and mutate rate p."
| pool parent |
parent := self newRandom.
pool := Array new: c+1.
[parent displayNl.
parent = Target] whileFalse:
[1 to: c do: [:i | pool at: i put: (parent copy mutate: p)].
pool at: c+1 put: parent.
parent := pool fold: [:winner :each | winner fittest: each]]]
Mutant class >> newRandom
[^(self new: Target size)
initializeToRandom;
yourself]
initializeToRandom
[self keys do: [:i | self at: i put: self randomLetter]]
mutate: p
[self keys do:
[:i |
Random next <= p ifTrue: [self at: i put: self randomLetter]]]
fitness
[| score |
score := 0.
self with: Target do:
[:me :you |
me = you ifTrue: [score := score + 1]].
^score]
fittest: aMutant
[^self fitness > aMutant fitness
ifTrue: [self]
ifFalse: [aMutant]]
randomLetter
[^Letters at: (Random between: 1 and: Letters size)]
]</lang>
Use example: <lang Smalltalk>st> Mutant run: 2500 rate: 0.1 QJUUIQHYXEZORSXGJCAHEWACH KG QJUUIQHYXEZORSXGJCAHEWWCMSKG QEUUIUHYXEZORSOGICAHYWWCSSKG QETUIUHGXEZORS GICE YWWCSSEG METUIUHSXOZORS OICE YWWCSSEG METUIUHSXOZORS OICE Y WCSSEG METUIUHSXOZMIS OIOE Y WCNSEG METKIUKSTOFMIS LIOE Y WCNSEG METKINKSTOFMIS LIKE E WCNSEG METKINKSTOFMIS LIKE F WCNSEL METHINKSTOF IS LIKE F WCNSEL METHINKS OW IS LIKE F WCNSEL METHINKS IW IS LIKE F WCNSEL METHINKS IW IS LIKE C WCASEL METHINKS IW IS LIKE C WCASEL METHINKS IW IS LIKE A WCASEL METHINKS IW IS LIKE A WCASEL METHINKS IW IS LIKE A WEASEL METHINKS IT IS LIKE A WEASEL Mutant</lang>
Swift
<lang swift>func evolve(
to target: String, parent: inout String, mutationRate: Int, copies: Int
) {
var parentFitness: Int {
return fitness(target: target, sentence: parent)
}
var generation = 0
while parent != target {
generation += 1
let bestOfGeneration =
(0..<copies)
.map({_ in mutate(sentence: parent, rate: mutationRate) })
.map({ (fitness(target: target, sentence: $0), $0) })
.sorted(by: { $0.0 < $1.0 })
.first!
if bestOfGeneration.0 < parentFitness {
print("Gen \(generation) produced better fit. \(bestOfGeneration.1) with fitness \(bestOfGeneration.0)")
parent = bestOfGeneration.1
}
}
}
func fitness(target: String, sentence: String) -> Int {
return zip(target, sentence).filter(!=).count
}
func mutate(sentence: String, rate: Int) -> String {
return String(
sentence.map({char in
if Int.random(in: 1...100) - rate <= 0 {
return "ABCDEFGHIJKLMNOPQRSTUVWXYZ ".randomElement()!
} else {
return char
}
})
)
}
let target = "METHINKS IT IS LIKE A WEASEL" let copies = 100 let mutationRate = 20
var start = mutate(sentence: target, rate: 100)
print("target: \(target)") print("Gen 0: \(start) with fitness \(fitness(target: target, sentence: start))")
evolve(to: target, parent: &start, mutationRate: mutationRate, copies: 100)</lang>
- Output:
target: METHINKS IT IS LIKE A WEASEL Gen 0: LODDQKXSYLDCNBEGKOOPAPNBQEVO with fitness 26 Gen 1 produced better fit. LVDDQKXS LLCIBEDKOOPAPNBQELO with fitness 24 Gen 2 produced better fit. LVDKQGXS LLCIBELKODPAPNBQELO with fitness 23 Gen 3 produced better fit. LVDKQGXS LLNISELKTEPAQNBQELO with fitness 21 Gen 4 produced better fit. LVDKQGXS ILMISELKREPA NBQELO with fitness 19 Gen 5 produced better fit. MHDKQGXS ILMISELKREPA NBQELO with fitness 18 Gen 7 produced better fit. MHDHQGXS ILMIS LKRHPA XBQELS with fitness 17 Gen 8 produced better fit. MHDHORXS IHMIS LIUHPA XBNEYS with fitness 16 Gen 9 produced better fit. MHDHORXS IHMIS LIMEPA XBNEYS with fitness 15 Gen 10 produced better fit. MKDHORRS IHMIS LIKEGA X MSYS with fitness 13 Gen 11 produced better fit. MKDHONRS IHMIS LIKEGA X MSYO with fitness 12 Gen 12 produced better fit. BDHONRS ILMIS LIKEGA T MSEL with fitness 11 Gen 13 produced better fit. GBPHONRS IQMIS LIKE A T MSEL with fitness 10 Gen 19 produced better fit. GOPHONKS IX IS LIKE A T QSEL with fitness 8 Gen 22 produced better fit. MOPHKNKS IX IS LIKE A TIQSEL with fitness 7 Gen 35 produced better fit. MEPHKNKS IX IS LIKE A TIQSEL with fitness 6 Gen 67 produced better fit. MEPHKNKS IX IS LIKE A TIASEL with fitness 5 Gen 132 produced better fit. MEPHINKS IZ IS LIKE A TIASEL with fitness 4 Gen 193 produced better fit. MEPHINKS IZ IS LIKE A TEASEL with fitness 3 Gen 572 produced better fit. MEPHINKS IT IS LIKE A TEASEL with fitness 2 Gen 579 produced better fit. MEPHINKS IT IS LIKE A WEASEL with fitness 1 Gen 937 produced better fit. METHINKS IT IS LIKE A WEASEL with fitness 0
Tailspin
<lang tailspin> def alphabet: [' ABCDEFGHIJKLMNOPQRSTUVWXYZ'...]; def target: ['METHINKS IT IS LIKE A WEASEL'...]; def generationSize: 100; def mutationPercent: 10;
source randomCharacter
$alphabet::length -> SYS::randomInt -> $alphabet($+1)!
end randomCharacter
templates countFitness
@:0;
$ -> \[i](when <=$target($i)> do @countFitness: $@countFitness + 1; \) -> !VOID
{ candidate: $, fitness: $@countFitness } !
end countFitness
sink evolve
@: {generation: 0"1", parent: $};
$@.parent -> #
when <{fitness: <=$target::length>}> do
'Target "$target...;" reached after $@.generation; generations' -> !OUT::write
otherwise
'Fitness $.fitness; at generation $@.generation;: "$.candidate...;"$#10;' -> !OUT::write
@.generation: $@.generation + 1;
1..$generationSize -> [$@.parent.candidate... -> \(
when <?(100 -> SYS::randomInt <..~$mutationPercent>)> do $randomCharacter!
otherwise $!
\)] -> countFitness -> \(when <{fitness: <$@evolve.parent.fitness..>}> do @evolve.parent: $;\) -> !VOID
$@.parent -> #
end evolve
[1..$target::length -> $randomCharacter] -> countFitness -> !evolve </lang>
- Output:
Fitness 1 at generation 0: "D MDIODAN FZQRCGYVTQWGBCFLRT" Fitness 3 at generation 1: "D MDIODANIFJQRCGYVTQWGBCFLET" Fitness 5 at generation 2: "D MDIODANITJQRCGYVTPWGBCFSET" Fitness 6 at generation 3: "D MDIODANITJQRCLYVTBWZBCKSET" ... Fitness 26 at generation 61: "VETHINKS IT SS LIKE A WEASEL" Fitness 26 at generation 62: "VETHINKS IT SS LIKE A WEASEL" Fitness 27 at generation 63: "GETHINKS IT IS LIKE A WEASEL" ... Fitness 27 at generation 209: "METHINKSFIT IS LIKE A WEASEL" Target "METHINKS IT IS LIKE A WEASEL" reached after 210 generations
Tcl
<lang tcl>package require Tcl 8.5
- A function to select a random character from an argument string
proc tcl::mathfunc::randchar s {
string index $s [expr {int([string length $s]*rand())}]
}
- Set up the initial variables
set target "METHINKS IT IS LIKE A WEASEL" set charset "ABCDEFGHIJKLMNOPQRSTUVWXYZ " set parent [subst [regsub -all . $target {[expr {randchar($charset)}]}]] set MaxMutateRate 0.91 set C 100
- Work with parent and target as lists of characters so iteration is more efficient
set target [split $target {}] set parent [split $parent {}]
- Generate the fitness *ratio*
proc fitness s {
global target
set count 0
foreach c1 $s c2 $target {
if {$c1 eq $c2} {incr count}
}
return [expr {$count/double([llength $target])}]
}
- This generates the converse of the Python version; logically saner naming
proc mutateRate {parent} {
expr {(1.0-[fitness $parent]) * $::MaxMutateRate}
} proc mutate {rate} {
global charset parent
foreach c $parent {
lappend result [expr {rand() <= $rate ? randchar($charset) : $c}]
} return $result
} proc que {} {
global iterations parent puts [format "#%-4i, fitness %4.1f%%, '%s'" \
$iterations [expr {[fitness $parent]*100}] [join $parent {}]] }
while {$parent ne $target} {
set rate [mutateRate $parent]
if {!([incr iterations] % 100)} que
set copies [list [list $parent [fitness $parent]]]
for {set i 0} {$i < $C} {incr i} {
lappend copies [list [set copy [mutate $rate]] [fitness $copy]]
} set parent [lindex [lsort -real -decreasing -index 1 $copies] 0 0]
} puts "" que</lang> Produces this example output:
#100 , fitness 42.9%, 'GSTBIGFS ITLSS LMD NNJPESZL' #200 , fitness 57.1%, 'SCTHIOAS ITHIS LNK PPLEASOG' #300 , fitness 64.3%, 'ILTHIBKS IT IS LNKE PPLEBSIS' #400 , fitness 96.4%, 'METHINKS IT IS LIKE A EASEL' #431 , fitness 100.0%, 'METHINKS IT IS LIKE A WEASEL'
Note that the effectiveness of the algorithm can be tuned by adjusting the mutation rate; with a Cadre size of 100, a very rapid convergence happens for a maximum mutation rate of 0.3…
Alternate Presentation
This alternative presentation factors out all assumption of what constitutes a “fit” solution to the fitness command, which is itself just a binding of the fitnessByEquality procedure to a particular target. None of the rest of the code knows anything about what constitutes a solution (and only mutate and fitness really know much about the data being evolved).
<lang tcl>package require Tcl 8.5
proc tcl::mathfunc::randchar {} {
# A function to select a random character
set charset "ABCDEFGHIJKLMNOPQRSTUVWXYZ "
string index $charset [expr {int([string length $charset] * rand())}]
} set target "METHINKS IT IS LIKE A WEASEL" set initial [subst [regsub -all . $target {[expr randchar()]}]] set MaxMutateRate 0.91 set C 100
- A place-wise equality function defined over two lists (assumed equal length)
proc fitnessByEquality {target s} {
set count 0
foreach c1 $s c2 $target {
if {$c1 eq $c2} {incr count}
}
return [expr {$count / double([llength $target])}]
}
- Generate the fitness *ratio* by place-wise equality with the target string
interp alias {} fitness {} fitnessByEquality [split $target {}]
- This generates the converse of the Python version; logically saner naming
proc mutationRate {individual} {
global MaxMutateRate
expr {(1.0-[fitness $individual]) * $MaxMutateRate}
}
- Mutate a string at a particular rate (per character)
proc mutate {parent rate} {
foreach c $parent {
lappend child [expr {rand() <= $rate ? randchar() : $c}]
} return $child
}
- Pretty printer
proc prettyPrint {iterations parent} {
puts [format "#%-4i, fitness %5.1f%%, '%s'" $iterations \
[expr {[fitness $parent]*100}] [join $parent {}]] }
- The evolutionary algorithm itself
proc evolve {initialString} {
global C
# Work with the parent as a list; the operations are more efficient
set parent [split $initialString {}]
for {set iterations 0} {[fitness $parent] < 1} {incr iterations} {
set rate [mutationRate $parent]
if {$iterations % 100 == 0} { prettyPrint $iterations $parent }
set copies [list [list $parent [fitness $parent]]] for {set i 0} {$i < $C} {incr i} { lappend copies [list \ [set copy [mutate $parent $rate]] [fitness $copy]] } set parent [lindex [lsort -real -decreasing -index 1 $copies] 0 0]
} puts "" prettyPrint $iterations $parent
return [join $parent {}]
}
evolve $initial</lang>
uBasic/4tH
This is a bit of a stretch, since uBasic/4tH doesn't support strings. Hence, the array is used to store the data. <lang>T = 0 ' Address of target L = 28 ' Length of string P = T + L ' Address of parent R = 6 ' Mutation rate in percent C = 7 ' Number of children B = 0 ' Best rate so far
Proc _Initialize ' Initialize
Do ' Now start mutating
I = 0 ' Nothing does it better so far
For x = 2 To C+1 ' Addresses of children Proc _MutateDNA (x, P, R) ' Now mutate their DNA F = FUNC(_Fitness (x, T)) ' Check for fitness If F > B Then B = F : I = x ' If fitness of child is better Next ' Make it the best score
If I Then ' If a better child was found Proc _MakeParent (P, I) ' Make the child the parent Proc _PrintParent (P) ' Print the new parent EndIf
Until B = L ' Until top score equals length
Loop
End
_MutateDNA Param(3) ' Mutate an entire DNA
Local(1)
For d@ = 0 to L-1 ' For the entire string
If c@ > Rnd(100) Then ' If mutation rate is met
@(a@*L+d@) = Ord("A") + Rnd(27) ' Mutate the gene
Else
@(a@*L+d@) = @(b@+d@) ' Otherwise copy it from the parent
EndIf
Next
Return
_Fitness Param(2) ' Check for fitness
Local(2)
c@ = 0 ' Fitness is zero For d@ = 0 to L-1 ' For the entire string If @(a@*L+d@) = @(b@+d@) Then c@ = c@ + 1 Next ' If string matches, increment score
Return (c@) ' Return the fitness
_MakeParent Param(2) ' Make a child into a parent
Local(1)
For c@ = 0 to L-1 ' For the entire string @(a@+c@) = @(b@*L+c@) ' Copy the DNA gene by gene Next
Return
_PrintParent Param(1) ' Print the parent
Local(1)
For b@ = 0 to L-1 ' For the entire string
If (@(a@+b@)) > Ord ("Z") Then
Print " "; ' Cater for the space
Else
Print CHR(@(a@+b@)); ' Print a gene
EndIf
Next
Print ' Issue a linefeed
Return
_Initialize ' Initialize target and parent
@(0)=Ord("M") ' Initialize target (long!)
@(1)=Ord("E") ' Character by character
@(2)=Ord("T")
@(3)=Ord("H")
@(4)=Ord("I")
@(5)=Ord("N")
@(6)=Ord("K")
@(7)=Ord("S")
@(8)=Ord("Z")+1
@(9)=Ord("I")
@(10)=Ord("T")
@(11)=Ord("Z")+1
@(12)=Ord("I")
@(13)=Ord("S")
@(14)=Ord("Z")+1
@(15)=Ord("L")
@(16)=Ord("I")
@(17)=Ord("K")
@(18)=Ord("E")
@(19)=Ord("Z")+1
@(20)=Ord("A")
@(21)=Ord("Z")+1
@(22)=Ord("W")
@(23)=Ord("E")
@(24)=Ord("A")
@(25)=Ord("S")
@(26)=Ord("E")
@(27)=Ord("L")
Proc _MutateDNA (P/L, P, 100) ' Now mutate the parent DNA
Return</lang>
- Output:
ZACXCLONTNTEAMJXYYFEP QQMDTA ZACXILONTBTEALJXYYFEP QQPDTA ZACNILONTBTEALJXYYXER WQPDTA ZACNILKNTBTEALJXYYXER WQPDTA ZACNILKNWBTEALJLYYXER WQPDTA ZACNIEKNYITEALJLYYPER WSPDTA ZACNIEKNYITEALJLYYPEA WSPDTA QYCNIEKNYITEALJLYYPEA WSPDTL MYCGIEKNYITEALJLYYPEA WSPDTL MYCGIGKN ITEALJLYYPEA WSUDTL MYCJIGKN ITEKLJLIYPEA WSUDTL MYCJIGKN ITEKLJLIYP A WSUDTL MYCJIGKN ITUKL LIYP A WSUDCL MYCJIGKS ITUKL LIYP A WSRDCL MYCJIGKS ITUUL LIYP A WSRDEL MYCJIGKS ITUUL LIYP A WSRSEL MYCJIGKS ITTUL LIYP A WWASEL MECJIGKS ITTUL LIYP A WWASEL MECHIGKS ITTUL LIYP A WWASEL MECHIGKS ITTUS LIYP A WWASEL MECHINKS ITTUS LIYP A WWASEL MECHINKS ITOUS LIYE A WWASEL MECHINKS ITOUS LIYE A WEASEL MECHINKS ITOIS LIYE A WEASEL MECHINKS ITOIS LIKE A WEASEL MECHINKS IT IS LIKE A WEASEL METHINKS IT IS LIKE A WEASEL 0 OK, 0:962
Ursala
The fitness function is given by the number of characters in the string not matching the target. (I.e., 0 corresponds to optimum fitness.) With characters mutated at a fixed probability of 10%, it takes about 500 iterations give or take 100.
<lang Ursala>#import std
- import nat
rand_char = arc ' ABCDEFGHIJKLMNOPQRSTUVWXYZ'
target = 'METHINKS IT IS LIKE A WEASEL'
parent = rand_char* target
fitness = length+ (filter ~=)+ zip/target
mutate("string","rate") = "rate"%~?(rand_char,~&)* "string"
C = 32
evolve = @iiX ~&l->r @r -*iota(C); @lS nleq$-&l+ ^(fitness,~&)^*C/~&h mutate\*10
- cast %s
main = evolve parent</lang> output:
'METHINKS IT IS LIKE A WEASEL'
UTFool
<lang UTFool> ··· http://rosettacode.org/wiki/Evolutionary_algorithm ··· ■ Evolutionary
§ static target⦂ String: "METHINKS IT IS LIKE A WEASEL" letter⦂ char[]: "ABCDEFGHIJKLMNOPQRSTUVWXYZ ".toCharArray° parent⦂ String random⦂ java.util.Random° rate⦂ double: 0.5 C⦂ int: 1000
▶ fittness⦂ int · computes the 'closeness' of its
• argument⦂ String · to the target string
closeness⦂ int: 0
∀ i ∈ 0 … target.length°
closeness◥ if target.charAt i = argument.charAt i
return closeness
▶ mutate⦂ String · returns a copy of the
• given⦂ String · with some characters probably mutated
• rate⦂ double
copy⦂ char[]: given.toCharArray°
∀ i ∈ 0 … given.length°
copy[i]: letter[random.nextInt letter.length] if rate > random.nextDouble°
return String.valueOf copy
▶ main
• args⦂ String[]
ancest⦂ StringBuilder°
∀ i ∈ 0 … target.length°
ancest.append letter[random.nextInt letter.length]
parent: ancest.toString°
currentFittness⦂ int: fittness parent
generation⦂ int: 0
🔁 until the parent ≈ target
if fittness parent > currentFittness
currentFittness: fittness parent
System.out.println "Fittness of generation #⸨generation⸩ is ⸨currentFittness⸩"
for each time from 1 to C
mutation⦂ String: mutate parent, rate
parent: mutation if fittness parent < fittness mutation
generation◥
System.out.println "Target reached by generation #⸨generation⸩"
</lang>
vbscript
<lang vbscript> 'This is the string we want to "evolve" to. Any string of any length will 'do as long as it consists only of upper case letters and spaces.
Target = "METHINKS IT IS LIKE A WEASEL"
'This is the pool of letters that will be selected at random for a mutation
letters = " ABCDEFGHIJKLMNOPQRSTUVWXYZ"
'A mutation rate of 0.5 means that there is a 50% chance that one letter 'will be mutated at random in the next child
mutation_rate = 0.5
'Set for 10 children per generation
Dim child(10)
'Generate the first guess as random letters
Randomize Parent = ""
for i = 1 to len(Target)
Parent = Parent & Mid(letters,Random(1,Len(letters)),1)
next
gen = 0
Do
bestfit = 0 bestind = 0
gen = gen + 1
'make n copies of the current string and find the one 'that best matches the target string
For i = 0 to ubound(child)
child(i) = Mutate(Parent, mutation_rate)
fit = Fitness(Target, child(i))
If fit > bestfit Then
bestfit = fit
bestind = i
End If
Next
'Select the child that has the best fit with the target string
Parent = child(bestind) Wscript.Echo parent, "(fit=" & bestfit & ")"
Loop Until Parent = Target
Wscript.Echo vbcrlf & "Generations = " & gen
'apply a random mutation to a random character in a string
Function Mutate ( ByVal str , ByVal rate )
Dim pos 'a random position in the string' Dim ltr 'a new letter chosen at random '
If rate > Rnd(1) Then
ltr = Mid(letters,Random(1,len(letters)),1)
pos = Random(1,len(str))
str = Left(str, pos - 1) & ltr & Mid(str, pos + 1)
End If
Mutate = str
End Function
'returns the number of letters in the two strings that match
Function Fitness (ByVal str , ByVal ref )
Dim i
Fitness = 0
For i = 1 To Len(str)
If Mid(str, i, 1) = Mid(ref, i, 1) Then Fitness = Fitness + 1
Next
End Function
'Return a random integer in the range lower to upper (inclusive)
Private Function Random ( lower , upper )
Random = Int((upper - lower + 1) * Rnd + lower)
End Function</lang>
Example output:
JTXBMMYUFUWTKJRVVNOGGUAIGSIF (fit=1) JTXBMMYUFYWTKJRVVNOGGUAIGSIF (fit=1) JTXKMMYUFYWTKJRVVNOGGUAIGSIF (fit=1) JTXKMMYUFYWTKJRVVNOGGUAIGSIF (fit=1) UTXKMMYUFYWTKJRVVNOGGUAIGSIF (fit=1) UTXKMMYUFYWTKJJVVNOGGUAIGSIF (fit=1) UTXKMMYUFYWTKJJVVNDGGUAIGSIF (fit=1) UTXKMMYUFYWTKJJVVNDGGUAIGSIF (fit=1) UTXKMMYUFYWTKJJVVNDGGUWIGSIF (fit=2) UTXKMMYUFYWTKJJVVNDGGUWIGSIF (fit=2) UTXKMMYUFYWTKJJVVNDGGUWIGSIF (fit=2) UBXKMMYUFYWTKJJVVNDGGUWIGSIF (fit=2) UBNKMMYUFYWTKJJVVNDGGUWIGSIF (fit=2) . . . METHINKS IT IS LIKEVA WEASEL (fit=27) METHINKS IT IS LIKEVA WEASEL (fit=27) METHINKS IT IS LIKEVA WEASEL (fit=27) METHINKS IT IS LIKEVA WEASEL (fit=27) METHINKS IT IS LIKEVA WEASEL (fit=27) METHINKS IT IS LIKE A WEASEL (fit=28) Generations = 580
Visual Basic
Adapted from BBC Basic Code in this page. One diference from BBC Basic code is that in this code mutations are always good <lang Visual Basic>
Option Explicit
Private Sub Main()
Dim Target
Dim Parent
Dim mutation_rate
Dim children
Dim bestfitness
Dim bestindex
Dim Index
Dim fitness
Target = "METHINKS IT IS LIKE A WEASEL"
Parent = "IU RFSGJABGOLYWF XSMFXNIABKT"
mutation_rate = 0.5
children = 10
ReDim child(children)
Do
bestfitness = 0
bestindex = 0
For Index = 1 To children
child(Index) = FNmutate(Parent, mutation_rate, Target)
fitness = FNfitness(Target, child(Index))
If fitness > bestfitness Then
bestfitness = fitness
bestindex = Index
End If
Next Index
Parent = child(bestindex)
Debug.Print Parent
Loop Until Parent = Target
End
End Sub
Function FNmutate(Text, Rate, ref)
Dim C As Integer
Dim Aux As Integer
If Rate > Rnd(1) Then
C = 63 + 27 * Rnd() + 1
If C = 64 Then C = 32
Aux = Len(Text) * Rnd() + 1
If Mid(Text, Aux, 1) <> Mid(ref, Aux, 1) Then
Text = Left(Text, Aux - 1) & Chr(C) & Mid(Text, Aux + 1)
End If
End If
FNmutate = Text
End Function Function FNfitness(Text, ref)
Dim I, F
For I = 1 To Len(Text)
If Mid(Text, I, 1) = Mid(ref, I, 1) Then F = F + 1
Next
FNfitness = F / Len(Text)
End Function </lang>
Example output:
U RFSGJABGOLYWF XSMFXNIABKT IU RFSGJABGOLYWF XSMFXNIABKT IU NFSGJABGOLYWF XSMFXNIABKT IU NFSGJABGOLYWF XSMFXNIABKT IU NFSGJABGOLYWF XSMFXNIABOT IUFNISGJABGOLYWF TSMFXCIABOT IUFNISGJABGOLYWF TSMFXCIABOT IUFNISGRABGOLYWF TSMFXCIABOT ..... IEFMI GUASGLOYWF DSMFPRIAROT IEFMI GUASGLOYWF DSMFPRZAROT IEFMI GUASGLOYWFFDSMFPRZAROT IEFMI GUASGLOYWFFDSMFPRZAQOT IEFMI GUASGLOYBFFDSMFPRZAQOT ..... METHINKS IT IS LVKE A WEASEL METHINKS IT IS LVKE A WEASEL METHINKS IT IS LRKE A WEASEL METHINKS IT IS LRKE A WEASEL METHINKS IT IS LRKE A WEASEL METHINKS IT IS LRKE A WEASEL METHINKS IT IS LIKE A WEASEL
Wren
<lang ecmascript>import "random" for Random
var target = "METHINKS IT IS LIKE A WEASEL" var set = "ABCDEFGHIJKLMNOPQRSTUVWXYZ " var rand = Random.new()
// fitness: 0 is perfect fit. greater numbers indicate worse fit. var fitness = Fn.new { |a| (0...target.count).count { |i| a[i] != target[i] } }
// set m to mutation of p, with each character of p mutated with probability r var mutate = Fn.new { |p, m, r|
var i = 0
for (ch in p) {
if (rand.float(1) < r) {
m[i] = set[rand.int(set.count)]
} else {
m[i] = ch
}
i = i + 1
}
}
var parent = List.filled(target.count, "") (0...parent.count).each { |i| parent[i] = set[rand.int(set.count)] } var c = 20 // number of times to copy and mutate parent var copies = List.filled(c, null) for (i in 0...c) copies[i] = List.filled(parent.count, 0) System.print(parent.join()) var best = fitness.call(parent) while (best > 0) {
for (cp in copies) mutate.call(parent, cp, 0.05)
for (cp in copies) {
var fm = fitness.call(cp)
if (fm < best) {
best = fm
parent = cp.toList
System.print(parent.join())
}
}
}</lang>
- Output:
Sample run:
ZVQWVAGAT RNLAEWCQOXWL L A D ZEQWVAGAT RNNAEWCQOXWL L RJD ZEQWIAGAT RNNAEWCQOXWL L RJD ZEQWIAGAT RNNAEWCQO WL L RJD MEPWIAGAT RNNAEWCZO WL I RJD METWIAGAT RNNAEWCZO WE I RJD METWIAGLT VNNPEWIZS WE I DJD METWIAGLT VNNPEWIKS WE I DJD METWIAGLT VNNJEWIKS WE I SJD METWIAGLT VNNJEQIKS WE E SJD METIIAGPT VNNSEQIKS WE E SBD METIIAGPT VNNSEQIKE WE E SBD METIIAGPT VNZSELIKE WE E SBD METIINKPT VNZSELIKE WE E SBD METIINKPT VNZS LIKE WE E SBD METIINKPV VIIS LIKE WE E SBD METIINKPV VIIS LIKE WE E SBL METIINKPV TIIS LIKE WE E SBL METIINKPV TIIS LIKE AE E SBL METHINKPV TVIS LIKE AE E SBL METHINKPV TVIS LIKE AEWE SDL METHINKPVITVIS LIKE AEWE SDL METHINKPVIT IS LIKE AEWE SDL METHINKPVIT IS LIKE AEWE SEL METHINKPVIT IS LIKE AEWEASEL METHINKPVIT IS LIKE A WEASEL METHINKSVIT IS LIKE A WEASEL METHINKS IT IS LIKE A WEASEL
XPL0
<lang XPL0>include c:\cxpl\codes; \intrinsic code declarations string 0; \use zero-terminated convention (instead of MSb)
def MutateRate = 15, \1 chance in 15 of a mutation
Copies = 30; \number of mutated copies
char Target, AlphaTbl; int SizeOfAlpha;
func StrLen(Str); \Return the number of characters in a string
char Str;
int I;
for I:= 0 to -1>>1-1 do
if Str(I) = 0 then return I;
func Unfitness(A, B); \Return number of characters different between A and B
char A, B;
int I, C;
[C:= 0;
for I:= 0 to StrLen(A)-1 do
if A(I) # B(I) then C:= C+1;
return C; ]; \Unfitness
proc Mutate(A, B); \Copy string A to B, but with each character of B having
char A, B; \ a 1 in MutateRate chance of differing from A
int I;
[for I:= 0 to StrLen(A)-1 do
B(I):= if Ran(MutateRate) then A(I) else AlphaTbl(Ran(SizeOfAlpha));
B(I):= 0; \terminate string ]; \Mutate
int I, BestI, Diffs, Best, Iter;
def SizeOfTarget = 28;
char Specimen(Copies, SizeOfTarget+1);
int ISpecimen, Temp;
[Target:= "METHINKS IT IS LIKE A WEASEL"; AlphaTbl:= "ABCDEFGHIJKLMNOPQRSTUVWXYZ "; SizeOfAlpha:= StrLen(AlphaTbl); ISpecimen:= Specimen; \integer accesses pointers rather than bytes
\Initialize first Specimen, the parent, to a random string for I:= 0 to SizeOfTarget-1 do
Specimen(0,I):= AlphaTbl(Ran(SizeOfAlpha));
Specimen(0,I):= 0; \terminate string
Iter:= 0; repeat for I:= 1 to Copies-1 do Mutate(ISpecimen(0), ISpecimen(I));
Best:= SizeOfTarget; \find best matching string
for I:= 0 to Copies-1 do
[Diffs:= Unfitness(Target, ISpecimen(I));
if Diffs < Best then [Best:= Diffs; BestI:= I];
];
if BestI \#0\ then \swap best string with first string
[Temp:= ISpecimen(0);
ISpecimen(0):= ISpecimen(BestI);
ISpecimen(BestI):= Temp;
];
Text(0, "Iter "); IntOut(0, Iter);
Text(0, " Score "); IntOut(0, Best);
Text(0, ": "); Text(0, ISpecimen(0)); CrLf(0);
Iter:= Iter+1;
until Best = 0; ]</lang>
Example output:
Iter 0 Score 26: YIOHAVRGQLXRZJOSHNPRY VIQDNK Iter 1 Score 25: YYOHAVRGQLX ZJOSHNPRY VIQDNK Iter 2 Score 24: YYOHAVRGQLX ZJOSHNPRY VIQSNK Iter 3 Score 24: YYOHAVRGQLX ZJOSHNPRY VIQSNK Iter 4 Score 23: YYOHAVRGQLX ZJOSHNERY VIQSNK Iter 5 Score 22: YYUHAVRGQLX ZJOSHNERY JDQSNL ... Iter 200 Score 1: METHINKS IT IS LIKE K WEASEL Iter 201 Score 1: METHINKS IT IS LIKE K WEASEL Iter 202 Score 1: METHINKS IT IS LIKE K WEASEL Iter 203 Score 0: METHINKS IT IS LIKE A WEASEL
zkl
<lang zkl>const target = "METHINKS IT IS LIKE A WEASEL"; const C = 100; // Number of children in each generation. const P = 0.05; // Mutation probability. const A2ZS = ["A".."Z"].walk().append(" ").concat(); fcn fitness(s){ Utils.zipWith('!=,target,s).sum(0) } // bigger is worser fcn rnd{ A2ZS[(0).random(27)] } fcn mutate(s){ s.apply(fcn(c){ if((0.0).random(1) < P) rnd() else c }) }
parent := target.len().pump(String,rnd); // random string of "A..Z " gen:=0; do{ // mutate C copies of parent and pick the fittest
parent = (0).pump(C,List,T(Void,parent),mutate)
.reduce(fcn(a,b){ if(fitness(a)<fitness(b)) a else b });
println("Gen %2d, dist=%2d: %s".fmt(gen+=1, fitness(parent), parent));
}while(parent != target);</lang>
- Output:
Gen 1, dist=26: JNGUIMCMOLLEULERIFPCYYZA JR Gen 2, dist=25: JNGUIMCMOLLEULERIFECYYZA JR Gen 3, dist=24: JNGUIMVMOLLEILERIFECYYZA JU ... Gen 7, dist=20: GNPHIMKMCLLEI ERIFECY ZA SJU Gen 8, dist=19: GNPHIMKMCLLEI ERIKECY Z SJH ... Gen 13, dist=14: CNTHIMKSCLHEIB RIKECY ME S L Gen 14, dist=14: CNTHIMKSCLHEIB RIKECY ME S L Gen 15, dist=14: CNTHIMKSCLHEIB RIKECY ME S L ... Gen 24, dist= 7: MLTHIMKS LTEIB MIKE Y WEASEL Gen 25, dist= 7: MLTHIMKS LTEIB MIKE Y WEASEL Gen 26, dist= 7: MLTHIMKS LTEIB KIKE Y WEASEL ... Gen 48, dist= 1: METHINKS IT IS LIKE Z WEASEL Gen 49, dist= 1: METHINKS IT IS LIKE G WEASEL Gen 50, dist= 0: METHINKS IT IS LIKE A WEASEL
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