Forest fire
Implement the Drossel and Schwabl definition of the forest-fire model.
You are encouraged to solve this task according to the task description, using any language you may know.
This page uses content from Wikipedia. The original article was at Forest-fire model. The list of authors can be seen in the page history. As with Rosetta Code, the text of Wikipedia is available under the GNU FDL. (See links for details on variance) |
It is basically a 2D cellular automaton where each cell can be in three distinct states (empty, tree and burning) and evolves according to the following rules (as given by Wikipedia)
- A burning cell turns into an empty cell
- A tree will burn if at least one neighbor is burning
- A tree ignites with probability f even if no neighbor is burning
- An empty space fills with a tree with probability p
Neighborhood is the Moore neighborhood; boundary conditions are so that on the boundary the cells are always empty ("fixed" boundary condition).
At the beginning, populate the lattice with empty and tree cells according to a specific probability (e.g. a cell has the probability 0.5 to be a tree). Then, let the system evolve.
Task's requirements do not include graphical display or the ability to change parameters (probabilities p and f) through a graphical or command line interface.
See also Conway's Game of Life and Wireworld.
6502 Assembly
<lang asm> ORG $4357
- SYS 17239 or CALL 17239
EMPTY2 = $00 TREE2 = $44 FIRE2 = $99
- common available zero page
GBASL = $26
GBASH = $27
SEED2 = $28 SEED0 = $29 SEED1 = $2A
H2 = $2B V2 = $2C PLOTC = $2D COLOR = $2E PAGE = $2F TOPL = $30 TOPH = $31 MIDL = $32 MIDH = $33 BTML = $34 BTMH = $35 PLOTL = $36 PLOTH = $37 lastzp = $38
tablelo = $5000 tablehi = tablelo+25
JSR START STA V2 LDA #$4C ; JMP instruction STA SEED2 ; temporary JMP LDX #$00 ; y coord table: TXA JSR SEED2 ; temporary JMP GBASCALC LDA GBASL STA tablelo,X LDA GBASH STA tablehi,X LDY #$00 TYA clrline: STA (GBASL),Y INY CPY #40 BNE clrline
INX CPX V2 BNE table
JSR sseed0 JSR sseed2
LDX #$60 STX PAGE STX TOPH LDY #$00 STY TOPL TYA zero: STA (TOPL),Y INY BNE zero INX STX TOPH CPX #$80 BNE zero
loop3: LDX #0 STX TOPL LDA #41 STA MIDL STA PLOTL LDA #83 STA BTML LDA PAGE STA TOPH STA MIDH STA BTMH EOR #$10 STA PLOTH STA PAGE loop2: TXA STX V2 LSR ; F800 PLOT-like... ; PHP ; F801 TAY ; save A in Y without touching C LDA #$0F BCC over2 ADC #$E0 over2: STA PLOTC ; PLOT... LDA tablelo,Y ; lookup instead of GBASCALC STA GBASL LDA tablehi,Y STA GBASH ; PLP ; continue PLOT LDY #$01 ; x coord loop1: STY H2 LDA (MIDL),Y STA (PLOTL),Y BEQ empty BPL tree LDA #EMPTY2 doplot: LDY H2 STA (PLOTL),Y DEY EOR (GBASL),Y AND PLOTC EOR (GBASL),Y STA (GBASL),Y noplot: LDY H2 INY CPY #41 BNE loop1 LDA MIDL STA TOPL LDA MIDH STA TOPH LDA BTML STA MIDL STA PLOTL CLC ADC #42 STA BTML LDA BTMH EOR #$10 STA PLOTH EOR #$10 STA MIDH ADC #$00 STA BTMH LDX V2 INX CPX #48 BNE loop2 JSR QUIT JMP loop3 empty: DEC SEED2 BNE noplot JSR sseed2 ; probability f LDA #TREE2 BNE doplot ignite: LDA #FIRE2 BNE doplot tree: DEC SEED0 BNE check DEC SEED1 BNE check JSR sseed0 ; probability p BNE ignite check: LDA (TOPL),Y ; n ORA (BTML),Y ; s DEY ORA (TOPL),Y ; nw ORA (MIDL),Y ; w ORA (BTML),Y ; sw INY INY ORA (TOPL),Y ; ne ORA (MIDL),Y ; e ORA (BTML),Y ; se BMI ignite BPL noplot
sseed0: LDA #$17 ; 1 in 10007 (prime) STA SEED0 LDA #$27 STA SEED1 RTS sseed2: LDA #$65 ; 1 in 101 (prime) STA SEED2 RTS
default: LDA #<GBASCALC ; setup GBASCALC STA SEED0 LDA #>GBASCALC STA SEED1 LDA #25 ; screen rows RTS GBASCALC: LDY #$00 STY GBASH ASL ASL ASL STA GBASL ASL ROL GBASH ASL ROL GBASH ADC GBASL STA GBASL LDA GBASH ADC #$04 STA GBASH RTS
QUIT: LDA $E000
- APPLE II
CMP #$4C BNE c64quit
BIT $C000 ; apple ii keypress? BPL CONTINUE ; no keypressed then continue BIT $C010 ; clear keyboard strobe BIT $C051 ; text mode
- end APPLE II specific
ABORT: PLA PLA
LDX #GBASL restorzp: LDA $5100,X STA $00,X INX CPX #lastzp BNE restorzp
CONTINUE: RTS
START: LDX #GBASL savezp: LDA $00,X STA $5100,X INX CPX #lastzp BNE savezp
- machine ???
LDA $E000 ; terribly unreliable, oh well
- APPLE II
CMP #$4C ; apple ii? BNE c64start ; nope, try another
BIT $C056 ; low resolution BIT $C052 ; full screen BIT $C054 ; page one BIT $C050 ; graphics
- GBASCALC = $F847
LDA #$47 STA SEED0 LDA #$F8 STA SEED1 LDA #24 ; screen rows RTS
- end APPLE II specific
- COMMODORE 64 specific
c64quit:
- COMMODORE 64
CMP #$85 ; commodore 64? BNE CONTINUE ; nope, default to no keypress
LDA $C6 ; commodore keyboard buffer length BEQ CONTINUE ; no keypressed then continue
LDA #$00 STA $C6 LDA $D016 ; Screen control register #2 AND #$EF ; Bit #4: 0 = Multicolor mode off. STA $D016 LDA #21 ; default character set STA $D018 BNE ABORT
c64start:
CMP #$85 ; commodore 64? BEQ c64yes ; yes JMP default ; no, default to boringness c64yes: LDA #$00 ; black STA $D020 ; border LDA #$00 ; black STA $D021 ; background LDA #$05 ; dark green STA $D022 ; Extra background color #1 LDA #$08 ; orange STA $D023 ; Extra background color #2 LDA $D016 ; Screen control register #2 ORA #$10 ; Bit #4: 1 = Multicolor mode on. STA $D016
LDA #$30 ; 0011 0000 $3000 charset page STA PLOTH LSR LSR STA PLOTC ; 0000 1100 #$0C
- 53272 $D018
- POKE 53272,(PEEK(53272)AND240)+12
- REM SET CHAR POINTER TO MEM. 12288
- Bits #1-#3
- In text mode, pointer to character memory
- (bits #11-#13), relative to VIC bank, memory address $DD00
- %110, 6
- $3000-$37FF, 12288-14335.
LDA $D018 AND #$F0 ORA PLOTC STA $D018
- setup nine characters
- 00- 00 00
LDA #$00 ; chr(0) * 8 STA PLOTL ; --- LDA #$00 ; already zero TAX ; LDX #$00 JSR charset
- 04- 00 55
LDA #32 ; chr(4) * 8 STA PLOTL LDA #$55 ; LDX #$00 ; already zero JSR charset
- 09- 00 AA
LDA #72 ; chr(9) * 8 STA PLOTL LDA #$AA ; LDX #$00 ; already zero JSR charset
- 40- 55 00
LDA PLOTH ; 512 = chr(64) * 8 CLC ADC #$02 STA PLOTH LDX #$00 STX PLOTL LDA #$00 LDX #$55 JSR charset
- 44- 55 55
LDA #32 ; chr(68) * 8 STA PLOTL TXA ; LDA #$55 ; LDX #$55 ; already 55 JSR charset
- 49- 55 AA
LDA #72 ; chr(73) * 8 STA PLOTL LDA #$AA ; LDX #$55 ; already 55 JSR charset
- 90- AA 00
LDA PLOTH ; chr(144) * 8 CLC ADC #$02 STA PLOTH LDA #128 STA PLOTL LDA #$00 LDX #$AA JSR charset
- 94- AA 55
LDA #160 ; chr(148) * 8 STA PLOTL LDA #$55 ; LDX #$AA ; already AA JSR charset
- 99- AA AA
LDA #200 ; chr(153) * 8 STA PLOTL TXA ; LDA #$AA ; LDX #$AA ; already AA JSR charset JMP default charset: LDY #$00 chartop: STA (PLOTL),Y INY CPY #$04 BNE chartop TXA charbtm: STA (PLOTL),Y INY CPY #$08 BNE charbtm RTS
- end COMMODORE 64 specific
</lang>
Ada
<lang Ada>with Ada.Numerics.Float_Random; use Ada.Numerics.Float_Random; with Ada.Text_IO; use Ada.Text_IO;
procedure Forest_Fire is
type Cell is (Empty, Tree, Fire); type Board is array (Positive range <>, Positive range <>) of Cell; procedure Step (S : in out Board; P, F : Float; Dice : Generator) is function "+" (Left : Boolean; Right : Cell) return Boolean is begin return Left or else Right = Fire; end "+"; function "+" (Left, Right : Cell) return Boolean is begin return Left = Fire or else Right = Fire; end "+"; Above : array (S'Range (2)) of Cell := (others => Empty); Left_Up, Up, Left : Cell; begin for Row in S'First (1) + 1..S'Last (1) - 1 loop Left_Up := Empty; Up := Empty; Left := Empty; for Column in S'First (2) + 1..S'Last (2) - 1 loop Left_Up := Up; Up := Above (Column); Above (Column) := S (Row, Column); case S (Row, Column) is when Empty => if Random (Dice) < P then S (Row, Column) := Tree; end if; when Tree => if Left_Up + Up + Above (Column + 1) + Left + S (Row, Column) + S (Row, Column + 1) + S (Row + 1, Column - 1) + S (Row + 1, Column) + S (Row + 1, Column + 1) or else Random (Dice) < F then S (Row, Column) := Fire; end if; when Fire => S (Row, Column) := Empty; end case; Left := Above (Column); end loop; end loop; end Step; procedure Put (S : Board) is begin for Row in S'First (1) + 1..S'Last (1) - 1 loop for Column in S'First (2) + 1..S'Last (2) - 1 loop case S (Row, Column) is when Empty => Put (' '); when Tree => Put ('Y'); when Fire => Put ('#'); end case; end loop; New_Line; end loop; end Put; Dice : Generator; Forest : Board := (1..10 => (1..40 => Empty));
begin
Reset (Dice); for I in 1..10 loop Step (Forest, 0.3, 0.1, Dice); Put_Line ("-------------" & Integer'Image (I) & " -------------"); Put (Forest); end loop;
end Forest_Fire;</lang> Sample output:
------------- 1 ------------- Y Y Y Y YY Y Y Y Y Y Y Y YYY YY Y Y Y Y Y Y YY Y Y Y Y Y Y Y Y YY Y Y Y Y YY Y YY YYY Y Y Y Y Y Y Y YY Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y YYY Y Y Y Y Y ------------- 2 ------------- Y Y Y YYYYY# YYY Y Y Y YYY Y Y Y YY# YYY YY Y Y Y Y #Y Y YY Y YYY YY Y YY# Y YY Y Y Y Y YY Y Y YY Y Y YYYY Y Y YYY YY Y Y Y#Y YYY YYYY YYY Y Y Y Y Y Y Y YYY Y# Y Y Y Y Y Y Y Y# Y Y Y Y Y YYY Y YY YY Y Y YYY YYYYY Y Y YY Y ------------- 3 ------------- YY # Y YYYY# YY# Y Y # YYY Y# Y Y Y# Y YYYYY Y# # YYY YYY #YY Y YY Y Y## Y#Y Y Y# YY YY YY # Y Y YYY # Y Y## # YYYYYY YYY YYYYYY YY Y Y YY # # YY# #YYYYYY YYYYY YY# Y YYY YYY Y# #YYY# YYY Y YY Y Y YY Y # Y# Y YY YYY Y YYYYY YY #Y YYY Y ### YYYY# YY YYYYY YY ------------- 4 ------------- ## Y YY## Y ## Y YYY Y YYY # Y Y # Y# ###YYY# Y ### YYYY #Y Y Y## Y # # # # # #YYYY Y# Y# YYYYYYYY Y YY YY# YY Y ##YYYY ##Y YYYYY#Y#Y YY#YYY Y Y Y# Y #YYYYYY YYYYY Y# Y YY#YYY#Y# ### Y YY #YY Y YY # Y #Y ## # Y# YYY# ##Y Y YYYYY Y YYY #YYY# YYY YYY# YYYYY#YY YY ------------- 5 ------------- Y # Y# Y #YYYYY #Y#YYY Y# Y Y# Y ### Y Y###Y # Y # Y Y Y Y Y #### # # #YY##### # ## ## Y##Y# #Y##Y # YYYY# # # Y# #Y#YY#Y#Y # YY ####Y# ##YYYY # # Y# ### # Y # ##Y ##Y# YY Y Y Y # # Y## # Y ###Y# Y Y## ### YYY Y Y## #YYY# #Y YYY ------------- 6 ------------- Y# YY # Y Y #####Y # #Y#Y # Y # Y#Y Y YY YYY# #Y #Y Y # # # # # Y ## Y# # Y # # Y #### # Y # ## # #Y ## Y # Y #YYY Y # Y#YYYY # # Y ##YY# # Y # Y Y Y Y# Y # Y Y # Y Y YY# YY Y# #Y# Y #Y#YY ------------- 7 ------------- Y# Y YY Y Y # Y # #Y Y# # # YY # YY YY## Y #Y #Y #Y Y Y Y Y #Y Y YY Y Y Y Y # Y Y YY YYY Y YY # YY Y # ###Y # Y # ####YY YY # ## Y# Y Y # # Y # YY Y#Y # # Y # Y Y# YYYY# Y # YY # #Y ------------- 8 ------------- # # #Y Y Y YYYY Y Y Y # # YYY YY Y ## Y# Y Y Y # Y #Y #Y Y #Y Y#YY #Y # #Y Y YY #Y Y Y # YYYYYY Y##Y Y Y Y YYYY Y Y Y YYY Y Y Y Y # YY # YY YY Y ##Y YYY##Y YYY # Y Y Y #Y YY#Y # # Y YY #Y Y YYY# # YY### Y YYY # ------------- 9 ------------- Y # YY YY####Y# YYYYYY # Y ### ## # Y # # Y Y YY # # Y #Y # #Y Y Y # # Y# #Y Y # Y # # YYYY ######YY# # Y Y# YY ###Y YY YYY # ### YY# # YY YY YYY YY Y Y # Y ### # ### Y YY Y Y Y Y Y #Y Y# #Y Y Y# # Y YY# Y# # Y #Y# YY ------------- 10 ------------- YYYY ## Y# # ##YYYYY Y# Y Y Y Y# # YYY YY #Y # # # Y Y Y # Y # YYYY Y# Y Y###Y ## Y Y# Y# #Y # ## YYY Y## ## YY YY ##Y YY YYY# Y Y# #Y # Y # Y Y # # # # # # Y YYY# # YY Y # #Y
ALGOL 68
Textual version
Note: This specimen retains the original D coding style.
<lang algol68>LONG REAL tree prob = 0.55, # original tree probability #
f prob = 0.01, # new combustion probability # p prob = 0.01; # tree creation probability #
MODE CELL = CHAR; CELL empty=" ", tree="T", burning="#"; MODE WORLD = [6, 65]CELL;
PROC has burning neighbours = (WORLD world, INT r, c)BOOL:(
FOR row shift FROM -1 TO 1 DO FOR col shift FROM -1 TO 1 DO INT rs = r + row shift, cs = c + col shift; IF rs >= LWB world AND rs <= UPB world AND cs >= 2 LWB world AND cs <= 2 UPB world THEN IF world[rs, cs] = burning THEN true exit FI FI OD OD; FALSE EXIT true exit: TRUE
);
PROC next state = (REF WORLD world, REF WORLD next world)VOID:(
FOR r FROM LWB world TO UPB world DO REF[]CELL row = world[r, ]; FOR c FROM LWB row TO UPB row DO REF CELL elem = row[c]; next world[r, c] := IF elem = empty THEN IF random<p prob THEN tree ELSE empty FI ELIF elem = tree THEN IF has burning neighbours(world, r, c) THEN burning ELSE IF random<f prob THEN burning ELSE tree FI FI ELIF elem = burning THEN empty FI OD OD; world := next world
);
main:(
WORLD world; # create world # FOR r FROM LWB world TO UPB world DO REF []CELL row = world[r, ]; FOR i FROM LWB row TO UPB row DO REF CELL el = row[i]; el := IF random < tree prob THEN tree ELSE empty FI OD OD;
WORLD next world; FOR i FROM 0 TO 4 DO next state(world, next world); printf(($n(2 UPB world)(a)l$, world)); # show world # printf(($gl$, 2 UPB world * "-")) OD
)</lang> Output:
TTTT T TTTT TT T T TTT TT TTT TT TTT T TT T T TTT TT T TT TTT TTTTT T T T TTTT T T TTT TT T T TT T T T TTT T T T T T T TT T # T T TTT T T T TTTTT T TTT TTTT TTTT TT T TT TTTTTTTTT TT TT T T TT T TT TTT TTT TTTT TT TTT TT TTTTTT T T T T T T TT TT TT #T TTT TT #TTTTTTTT TT TTT TTTTTTTTTT TT TTTTTT TT T TT T TTT T TT T TT # T T ----------------------------------------------------------------- TTTT T TTTT TT T T TTT TT TTT TT TTT T TT T T TTT TT T TT TTT TTTTT T T T ##TT T T TTT TT T T TT T T T TTT T T T T T T TT T T T TTT T T T TTTTT T TTT TTTT TTTT TT T T# TTTTTTT## TT TT T T TT T T# #TT TTT T### TT TTT TT TTTTTT T T T T T T TT TT TTT # TTT TT #TTTTTTT TT TTT TTTTTTTTTT TT TTTTTT TT T TT T TTT # TT T TT T T ----------------------------------------------------------------- TTTT T TTTT TT T T ### TT TTT TT TTT T TT T T TTT TT T TT TTT TTTTT T T T #T T T TTT TT T T TT T T T TT# T T T T T T ## T T T TTT T T T ##### T TT# ##TT TTTT TT T # TTTTTT# TT TT T T TT TT # #T TTT # TT TTT TT T#T### T T # T T T TT TT TT# TTT T# #TTTTTT TT TTT TTTTTTTTTT TT TTTTTT TT T TT T TTT #T T TTT T T ----------------------------------------------------------------- TTTT T TTTT TT T T #T TTT TT TTT T TT T T TTT TT # TT TTT TTTT# # T # # T T TTT TT # # ## T # # ## T T T T T T T # T TTT T T T T T# ## TTTT TT # #TTTT# TT TT T T TT TT # TTT #T TTT TT # # T # T T T TT TT T# #TT # #TTTTT TT TTT ######TTTT T# #TTTTT TT T TT T T## # T ### # T ----------------------------------------------------------------- #TTT T T### ## T # # TTT TT TTT T ## # # ### ## TT TTT TTT# T T T TTT TT T T T T T # # T T TTT T T T T# # TTTT TT #TT# ## TT T T TT T# TT# # TTT TT T # T T TT TT # #T #TTTT TT TT# #TT# # #TTTT TT T TT T # T T -----------------------------------------------------------------
AutoHotkey
This implementation uses AutoHotkey's pseudo-arrays to contain each cell. The size of the (square) map, probabilities, and characters which correspond to burning, tree, or empty can be edited at the beginning of the script. <lang AutoHotkey>
- The array Frame1%x%_%y% holds the current frame. frame2%x%_%y%
- is then calculated from this, and printed. frame2 is then copied to frame1.
- Two arrays are necessary so that each cell advances at the same time
- T=Tree, #=Fire, O=Empty cell
- Size holds the width and height of the map and is used as the # of iterations in loops
- This will save the map as forest_fire.txt in its working directory
- ======================================================================================
Size := 10
Generation := 0
Tree := "T"
Fire := "#"
Cell := "O"
- --Define probabilities--
New_Tree := 5 ; 20 percent chance (1 in 5). A random number will be generated from 1 to New_tree. If this number is 1, ; A tree will be created in the current cell
Spontaneous := 10 ; 10 percent chance (1 in 10). A random number will be generated from 1 to Spontaneous. If this number is 1, ; and the current cell contains a tree, the tree in the current cell will become fire.
GoSub, Generate
- ----------------------Main Loop------------------------------
loop {
Generation++ GoSub, Calculate GoSub, Copy GoSub, Display msgbox, 4, Forest Fire, At Generation %generation%. Continue? IfMsgbox, No ExitApp
} return
- -------------------------------------------------------------
Generate: ; Randomly initializes the map. loop % size ; % forces expression mode. { x := A_Index Loop % size { Y := A_Index Random, IsTree, 1, 2 ; -- Roughly half of the spaces will contain trees If ( IsTree = 1 ) Frame1%x%_%y% := Tree Else Frame1%x%_%y% := Cell } } return
Calculate: Loop % size { x := A_Index Loop % size { Y := A_Index If ( Frame1%x%_%y% = Cell ) { Random, tmp, 1, New_Tree If ( tmp = 1 ) Frame2%x%_%y% := tree Else Frame2%x%_%y% := Cell } Else If ( Frame1%x%_%y% = Tree ) { BoolCatch := PredictFire(x,y) If (BoolCatch) Frame2%x%_%y% := Fire Else Frame2%x%_%y% := Tree } Else If ( Frame1%x%_%y% = Fire ) Frame2%x%_%y% := Cell Else { contents := Frame1%x%_%y% Msgbox Error! Cell %x% , %y% contains %contents% ; This has never happened ExitApp } } } return
Copy: Loop % size { x := A_Index Loop % size { y := A_Index frame1%x%_%y% := Frame2%x%_%y% } } return
Display:
ToPrint := ""
ToPrint .= "=====Generation " . Generation . "=====`n"
Loop % size
{
x := A_Index
Loop % size
{
y := A_Index
ToPrint .= Frame1%x%_%y%
}
ToPrint .= "`n"
}
FileAppend, %ToPrint%, Forest_Fire.txt
Return
PredictFire(p_x,p_y){
Global ; allows access to all frame1*_* variables (the pseudo-array) A := p_x-1 B := p_y-1 C := p_x+1 D := p_y+1 If ( Frame1%A%_%p_Y% = fire ) return 1 If ( Frame1%p_X%_%B% = fire ) return 1 If ( Frame1%C%_%p_Y% = fire ) return 1 If ( Frame1%p_X%_%D% = fire ) return 1
If ( Frame1%A%_%B% = Fire ) return 1 If ( Frame1%A%_%D% = fire ) return 1 If ( Frame1%C%_%B% = fire ) return 1 If ( Frame1%C%_%D% = Fire ) return 1
Random, tmp, 1, spontaneous if ( tmp = 1 ) return 1 return 0
} </lang> Sample Output using the default settings:
=====Generation 1===== OTTTOOTOOT OTOOTTTTOT TTOOOTTTO# TOOTOTOOTT OTTOTOOTTO TOTTTTOOTO TOTTT#OOOT OT#OOTOOTT TTO#TOOTTT O#OOOTOTTT =====Generation 2===== OTTTOOTOOT OTTOTTT#O# TTOOOTTTOO TOOTTTOT## OTTOTTO##O TOTT##OTTO TO###OOOOT T#OOO#OOTT ##TO#OOTTT TOTOOTOTTT =====Generation 3===== OTT#OO#TO# OTTOTT#OTO TTOOOT##OO TOOTTTT#OO OTTO##OOOO TO##OOO##O #OOOOOOOOT #OOOOOOOTT OO#OOTOTTT #O#TT#OTTT =====Generation 4===== OT#OOOO#OO OT#O##OO#T T#TOT#OOOO TOO####OOT O##OOOOOOO #OOOOOOOOO OOOOOOOOO# OTOOOOOOTT OOOOO#TTTT OTO##OO#TT =====Generation 5===== O#OOOTOOOT O#OOOOOOO# #O#O#OOTOT #OOOOOOOOT OOOOOOOOOO OTOOOOOOOO TTOOOTOTTO TTOOOTOO## OOTTOO###T OTOOOOOO#T
BASIC256
<lang basic256>N = 150 : M = 150 : P = 0.03 : F = 0.00003
dim f(N+2,M+2) # 1 tree, 0 empty, 2 fire dim fn(N+2,M+2) graphsize N,M fastgraphics
for x = 1 to N for y = 1 to M if rand<0.5 then f[x,y] = 1 next y next x
while True for x = 1 to N for y = 1 to M if not f[x,y] and rand<P then fn[x,y]=1 if f[x,y]=2 then fn[x,y]=0 if f[x,y]=1 then fn[x,y] = 1 if f[x-1,y-1]=2 or f[x,y-1]=2 or f[x+1,y-1]=2 then fn[x,y]=2 if f[x-1,y]=2 or f[x+1,y]=2 or rand<F then fn[x,y]=2 if f[x-1,y+1]=2 or f[x,y+1]=2 or f[x+1,y+1]=2 then fn[x,y]=2 end if # Draw if fn[x,y]=0 then color black if fn[x,y]=1 then color green if fn[x,y]=2 then color yellow plot x-1,y-1 next y next x refresh for x = 1 to N for y = 1 to M f[x,y] = fn[x,y] next y next x end while</lang>
BBC BASIC
<lang bbcbasic> VDU 23,22,400;400;16,16,16,128
OFF DIM old&(200,200), new&(200,200) p = 0.01 f = 0.0001 REM 0 = empty, 1 = tree, 2 = burning REPEAT WAIT 10 FOR x% = 1 TO 199 FOR y% = 1 TO 199 CASE old&(x%,y%) OF WHEN 0: IF p > RND(1) THEN new&(x%,y%) = 1 GCOL 2 PLOT 4*x%,4*y% ENDIF WHEN 1: IF f > RND(1) OR old&(x%-1,y%)=2 OR old&(x%+1,y%)=2 OR \ \ old&(x%-1,y%-1)=2 OR old&(x%,y%-1)=2 OR old&(x%+1,y%-1)=2 OR \ \ old&(x%-1,y%+1)=2 OR old&(x%,y%+1)=2 OR old&(x%+1,y%+1)=2 THEN new&(x%,y%) = 2 GCOL 1 PLOT 4*x%,4*y% ENDIF WHEN 2: new&(x%,y%) = 0 GCOL 15 PLOT 4*x%,4*y% ENDCASE NEXT NEXT x% old&() = new&() UNTIL FALSE</lang>
Output:
C
<lang c>#include <stdio.h>
- include <stdlib.h>
- include <stdint.h>
- include <stdbool.h>
- include <string.h>
- include <pthread.h>
- include <SDL.h>
// defaults
- define PROB_TREE 0.55
- define PROB_F 0.00001
- define PROB_P 0.001
- define TIMERFREQ 100
- ifndef WIDTH
- define WIDTH 640
- endif
- ifndef HEIGHT
- define HEIGHT 480
- endif
- ifndef BPP
- define BPP 32
- endif
- if BPP != 32
#warning This program could not work with BPP different from 32
- endif
uint8_t *field[2], swapu; double prob_f = PROB_F, prob_p = PROB_P, prob_tree = PROB_TREE;
enum cell_state {
VOID, TREE, BURNING
};
// simplistic random func to give [0, 1) double prand() {
return (double)rand() / (RAND_MAX + 1.0);
}
// initialize the field void init_field(void) {
int i, j; swapu = 0; for(i = 0; i < WIDTH; i++) { for(j = 0; j < HEIGHT; j++) { *(field[0] + j*WIDTH + i) = prand() > prob_tree ? VOID : TREE; } }
}
// the "core" of the task: the "forest-fire CA" bool burning_neighbor(int, int); pthread_mutex_t synclock = PTHREAD_MUTEX_INITIALIZER; static uint32_t simulate(uint32_t iv, void *p) {
int i, j;
/* Since this is called by SDL, "likely"(*) in a separated thread, we try to avoid corrupted updating of the display (done by the show() func): show needs the "right" swapu i.e. the right complete field. (*) what if it is not so? The following is an attempt to avoid unpleasant updates. */ pthread_mutex_lock(&synclock);
for(i = 0; i < WIDTH; i++) { for(j = 0; j < HEIGHT; j++) { enum cell_state s = *(field[swapu] + j*WIDTH + i); switch(s) { case BURNING:
*(field[swapu^1] + j*WIDTH + i) = VOID; break;
case VOID:
*(field[swapu^1] + j*WIDTH + i) = prand() > prob_p ? VOID : TREE; break;
case TREE:
if (burning_neighbor(i, j)) *(field[swapu^1] + j*WIDTH + i) = BURNING; else *(field[swapu^1] + j*WIDTH + i) = prand() > prob_f ? TREE : BURNING; break;
default:
fprintf(stderr, "corrupted field\n"); break;
} } } swapu ^= 1; pthread_mutex_unlock(&synclock); return iv;
}
// the field is a "part" of an infinite "void" region
- define NB(I,J) (((I)<WIDTH)&&((I)>=0)&&((J)<HEIGHT)&&((J)>=0) \
? (*(field[swapu] + (J)*WIDTH + (I)) == BURNING) : false) bool burning_neighbor(int i, int j) {
return NB(i-1,j-1) || NB(i-1, j) || NB(i-1, j+1) || NB(i, j-1) || NB(i, j+1) || NB(i+1, j-1) || NB(i+1, j) || NB(i+1, j+1);
}
// "map" the field into gfx mem
// burning trees are red
// trees are green
// "voids" are black;
void show(SDL_Surface *s)
{
int i, j; uint8_t *pixels = (uint8_t *)s->pixels; uint32_t color; SDL_PixelFormat *f = s->format;
pthread_mutex_lock(&synclock); for(i = 0; i < WIDTH; i++) { for(j = 0; j < HEIGHT; j++) { switch(*(field[swapu] + j*WIDTH + i)) { case VOID:
color = SDL_MapRGBA(f, 0,0,0,255); break;
case TREE:
color = SDL_MapRGBA(f, 0,255,0,255); break;
case BURNING:
color = SDL_MapRGBA(f, 255,0,0,255); break;
} *(uint32_t*)(pixels + j*s->pitch + i*(BPP>>3)) = color; } } pthread_mutex_unlock(&synclock);
}
int main(int argc, char **argv) {
SDL_Surface *scr = NULL; SDL_Event event[1]; bool quit = false, running = false; SDL_TimerID tid;
// add variability to the simulation srand(time(NULL));
// we can change prob_f and prob_p // prob_f prob of spontaneous ignition // prob_p prob of birth of a tree double *p; for(argv++, argc--; argc > 0; argc--, argv++) { if ( strcmp(*argv, "prob_f") == 0 && argc > 1 ) { p = &prob_f; } else if ( strcmp(*argv, "prob_p") == 0 && argc > 1 ) { p = &prob_p; } else if ( strcmp(*argv, "prob_tree") == 0 && argc > 1 ) { p = &prob_tree; } else continue;
argv++; argc--; char *s = NULL; double t = strtod(*argv, &s); if (s != *argv) *p = t; }
printf("prob_f %lf\nprob_p %lf\nratio %lf\nprob_tree %lf\n",
prob_f, prob_p, prob_p/prob_f, prob_tree);
if ( SDL_Init(SDL_INIT_VIDEO|SDL_INIT_TIMER) != 0 ) return EXIT_FAILURE; atexit(SDL_Quit);
field[0] = malloc(WIDTH*HEIGHT); if (field[0] == NULL) exit(EXIT_FAILURE); field[1] = malloc(WIDTH*HEIGHT); if (field[1] == NULL) { free(field[0]); exit(EXIT_FAILURE); }
scr = SDL_SetVideoMode(WIDTH, HEIGHT, BPP, SDL_HWSURFACE|SDL_DOUBLEBUF); if (scr == NULL) { fprintf(stderr, "SDL_SetVideoMode: %s\n", SDL_GetError()); free(field[0]); free(field[1]); exit(EXIT_FAILURE); }
init_field();
tid = SDL_AddTimer(TIMERFREQ, simulate, NULL); // suppose success running = true;
event->type = SDL_VIDEOEXPOSE; SDL_PushEvent(event);
while(SDL_WaitEvent(event) && !quit) { switch(event->type) { case SDL_VIDEOEXPOSE: while(SDL_LockSurface(scr) != 0) SDL_Delay(1); show(scr); SDL_UnlockSurface(scr); SDL_Flip(scr); event->type = SDL_VIDEOEXPOSE; SDL_PushEvent(event); break; case SDL_KEYDOWN: switch(event->key.keysym.sym) { case SDLK_q:
quit = true; break;
case SDLK_p:
if (running) { running = false; pthread_mutex_lock(&synclock); SDL_RemoveTimer(tid); // ignore failure... pthread_mutex_unlock(&synclock); } else { running = true; tid = SDL_AddTimer(TIMERFREQ, simulate, NULL); // suppose success... } break;
} case SDL_QUIT: quit = true; break; } }
if (running) { pthread_mutex_lock(&synclock); SDL_RemoveTimer(tid); pthread_mutex_unlock(&synclock); } free(field[0]); free(field[1]); exit(EXIT_SUCCESS);
}</lang>
Console version
C99. Uncomment srand() for variaty, usleep() for slower speed. <lang C>#include <stdio.h>
- include <stdlib.h>
- include <unistd.h>
enum { empty = 0, tree = 1, fire = 2 }; const char *disp[] = {" ", "\033[32m/\\\033[m", "\033[07;31m/\\\033[m"}; double tree_prob = 0.01, burn_prob = 0.0001;
- define for_x for (int x = 0; x < w; x++)
- define for_y for (int y = 0; y < h; y++)
- define for_yx for_y for_x
- define chance(x) (rand() < RAND_MAX * x)
void evolve(int w, int h) { unsigned univ[h][w], new[h][w]; for_yx new[y][x] = univ[y][x] = chance(tree_prob) ? tree : empty;
show: printf("\033[H"); for_y { for_x printf(disp[univ[y][x]]); printf("\033[E"); } fflush(stdout);
for_yx { switch (univ[y][x]) { case fire: new[y][x] = empty; break; case empty: if (chance(tree_prob)) new[y][x] = tree; break; default: for (int y1 = y - 1; y1 <= y + 1; y1++) { if (y1 < 0 || y1 >= h) continue; for (int x1 = x - 1; x1 <= x + 1; x1++) { if (x1 < 0 || x1 >= w) continue; if (univ[y1][x1] != fire) continue;
new[y][x] = fire; goto burn; } }
burn: if (new[y][x] == tree && chance(burn_prob)) new[y][x] = fire; } }
for_yx { univ[y][x] = new[y][x]; } //usleep(100000); goto show; }
int main(int c, char **v) { //srand(time(0)); int w = 0, h = 0;
if (c > 1) w = atoi(v[1]); if (c > 2) h = atoi(v[2]); if (w <= 0) w = 30; if (h <= 0) h = 30;
evolve(w, h); }</lang>
C#
<lang c sharp>using System;
namespace ForestFire {
internal class Program { private static void Main(string[] args) { Console.Write("Height? "); int height = int.Parse(Console.ReadLine()); Console.Write("Width? "); int width = int.Parse(Console.ReadLine()); Console.Write("Probability of a tree spontaneously combusting? 1/"); int f = int.Parse(Console.ReadLine()); Console.Write("Probability of a tree growing? 1/"); int p = int.Parse(Console.ReadLine()); Console.Clear();
var state = InitializeForestFire(height, width);
uint generation = 0;
do { state = StepForestFire(state, f, p);
Console.SetCursorPosition(0, 0); Console.ResetColor(); Console.WriteLine("Generation " + ++generation);
for (int y = 0; y < height; y++) { for (int x = 0; x < width; x++) { switch (state[y, x]) { case CellState.Empty: Console.Write(' '); break; case CellState.Tree: Console.ForegroundColor = ConsoleColor.DarkGreen; Console.Write('T'); break; case CellState.Burning: Console.ForegroundColor = ConsoleColor.DarkRed; Console.Write('F'); break; } }
Console.WriteLine(); } } while (Console.ReadKey(true).Key != ConsoleKey.Q && generation < uint.MaxValue); }
private static CellState[,] InitializeForestFire(int height, int width) { // Create our state array, initialize all indices as Empty, and return it. var state = new CellState[height, width]; state.Initialize(); return state; }
private enum CellState : byte { Empty = 0, Tree = 1, Burning = 2 }
private static readonly Random Random = new Random();
private static CellState[,] StepForestFire(CellState[,] state, int f, int p) { /* Clone our old state, so we can write to our new state * without changing any values in the old state. */ var newState = (CellState[,]) state.Clone();
int height = state.GetLength(0); int width = state.GetLength(1);
for (int i = 1; i < height - 1; i++) { for (int o = 1; o < width - 1; o++) { /* * Check the current cell. * * If it's empty, give it a 1/p chance of becoming a tree. * * If it's a tree, check to see if any neighbors are burning. * If so, set the cell's state to burning, otherwise give it * a 1/f chance of combusting. * * If it's burning, set it to empty. */ switch (state[i, o]) { case CellState.Empty: if (Random.Next(0, p) == 0) newState[i, o] = CellState.Tree; break; case CellState.Tree: if (IsNeighbor(state, i, o, CellState.Burning) || Random.Next(0, f) == 0) newState[i, o] = CellState.Burning; break; case CellState.Burning: newState[i, o] = CellState.Empty; break; } } }
return newState; }
private static bool IsNeighbor(CellState[,] state, int x, int y, CellState value) { // Check each cell within a 1 cell radius for the specified value. for (int i = -1; i <= 1; i++) { for (int o = -1; o <= 1; o++) { if (i == 0 && o == 0) continue;
if (state[x + i, y + o] == value) return true; } }
return false; } }
}</lang>
Sample Output
Generation 10 T T T T TF F T TFTFFTTTFTF F TT F FTTTTTT TF F FFT FFTT TTFFT T FF F T FF T F F TF T FFF TTTT T TFTF F F T TT TFT F TTT TT TTTTTTTT F FTFT F TTTTF F TF FF F FF TTTT F F F F T TTTT TTFFF T TFFTT TTTTTTT T T F F TTT TTTTTTFFTF FTFFFFFFTT T FTT TT TFFFFFTFTTTTTT T TFFT FF FF FTTTTT T F T FFT T T T TF FTFFT FTF TF T F F F FTF T T FT FF FTFTTFT TTFTTTTT F TT F TT TTTFFFF T F TTTF T TFTFTF TFT F T TFFFFF T F FT FF F TTTTTTTT TT FTFT F F
Clojure
<lang Clojure> (def burn-prob 0.1) (def new-tree-prob 0.5)
(defn grow-new-tree? [] (> new-tree-prob (rand))) (defn burn-tree? [] (> burn-prob (rand))) (defn tree-maker [] (if (grow-new-tree?) :tree :grass))
(defn make-forest
([] (make-forest 5)) ([size] (take size (repeatedly #(take size (repeatedly tree-maker))))))
(defn tree-at [forest row col] (try (-> forest
(nth row) (nth col)) (catch Exception _ false)))
(defn neighbores-burning? [forest row col]
(letfn [(burnt? [row col] (= :burnt (tree-at forest row col)))] (or (burnt? (inc row) col) (burnt? (dec row) col) (burnt? row (inc col)) (burnt? row (dec col)))))
(defn lightning-strike [forest]
(map (fn [forest-row] (map #(if (and (= % :tree) (burn-tree?)) :fire! %) forest-row) ) forest))
(defn burn-out-trees [forest]
(map (fn [forest-row] (map #(case % :burnt :grass :fire! :burnt %) forest-row)) forest))
(defn burn-neighbores [forest]
(let [forest-size (count forest) indicies (partition forest-size (for [row (range forest-size) col (range forest-size)] (cons row (list col))))] (map (fn [forest-row indicies-row] (map #(if (and (= :tree %) (neighbores-burning? forest (first %2) (second %2))) :fire! %) forest-row indicies-row)) forest indicies)))
(defn grow-new-trees [forest] (map (fn [forest-row]
(map #(if (= % :grass) (tree-maker) %) forest-row)) forest))
(defn forest-fire
([] (forest-fire 5)) ([forest-size] (loop [forest (make-forest forest-size)] (pprint forest) (Thread/sleep 300) (-> forest (burn-out-trees) (lightning-strike) (burn-neighbores) (grow-new-trees) (recur)))))
(forest-fire)
</lang>
example output
((:tree :tree :grass :tree :tree) (:tree :grass :tree :tree :tree) (:fire! :tree :tree :grass :tree) (:fire! :fire! :tree :tree :tree) (:burnt :tree :tree :fire! :grass)) ((:tree :tree :grass :tree :tree) (:fire! :tree :tree :fire! :tree) (:burnt :fire! :tree :grass :tree) (:burnt :burnt :fire! :fire! :tree) (:grass :fire! :fire! :burnt :tree))
Common Lisp
<lang lisp>(defvar *dims* '(10 10)) (defvar *prob-t* 0.5) (defvar *prob-f* 0.1) (defvar *prob-p* 0.01)
(defmacro with-gensyms (names &body body)
`(let ,(mapcar (lambda (n) (list n '(gensym))) names)
,@body))
(defmacro traverse-grid (grid rowvar colvar (&rest after-cols) &body body)
(with-gensyms (dims rows cols)
`(let* ((,dims (array-dimensions ,grid)) (,rows (car ,dims)) (,cols (cadr ,dims))) (dotimes (,rowvar ,rows ,grid) (dotimes (,colvar ,cols ,after-cols) ,@body)))))
(defun make-new-forest (&optional (dims *dims*))
(let ((forest (make-array dims :element-type 'symbol :initial-element 'void)))
(traverse-grid forest row col nil (if (<= (random 1.0) *prob-t*) (setf (aref forest row col) 'tree)))))
(defun print-forest (forest)
(traverse-grid forest row col (terpri)
(ecase (aref forest row col) ((void) (write-char #\space)) ((tree) (write-char #\T)) ((fire) (write-char #\#))))
(values))
(defvar *neighboring* '((-1 . -1) (-1 . 0) (-1 . 1) (0 . -1) (0 . 1) (1 . -1) (1 . 0) (1 . 1)))
(defun neighbors (forest row col)
(loop for n in *neighboring*
for nrow = (+ row (car n))
for ncol = (+ col (cdr n))
when (array-in-bounds-p forest nrow ncol) collect (aref forest nrow ncol)))
(defun evolve-tree (forest row col)
(let ((tree (aref forest row col)))
(cond ((eq tree 'fire) ;; if the tree was on fire, it's dead Jim 'void) ((and (eq tree 'tree) ;; if a neighbor is on fire, it's on fire too (find 'fire (neighbors forest row col) :test #'eq)) 'fire) ((and (eq tree 'tree) ;; random chance of fire happening (<= (random 1.0) *prob-f*)) 'fire) ((and (eq tree 'void) ;; random chance of empty space becoming a tree (<= (random 1.0) *prob-p*)) 'tree) (t tree))))
(defun evolve-forest (forest)
(let* ((dims (array-dimensions forest))
(new (make-array dims :element-type 'symbol :initial-element 'void))) (traverse-grid forest row col nil (setf (aref new row col) (evolve-tree forest row col))) new))
(defun simulate (forest n &optional (print-all t))
(format t "------ Initial forest ------~%") (print-forest forest) (dotimes (i n) (setf forest (evolve-forest forest)) (when print-all (progn (format t "~%------ Generation ~d ------~%" (1+ i)) (print-forest forest)))))
</lang> Example results: <lang lisp>CL-USER>(defparameter *forest* (make-new-forest)) CL-USER>(simulate *forest* 5)
Initial forest ------
TTTTT TT
TTT TT TT T T TTTT T TT
T TT T T
T TTT TTTT TTT T T T T T
TTT TTT T
Generation 1 ------
TTTTT TT
TTT TT TT T T TTTT T TT
T TT T T
T TTT TTTT TTT T T T T T
TTT TTT T
Generation 2 ------
TTTTT TT
TTT TT TT T T TTTT T TT
TTTT T T
T TTT TTT# TTT T T T T T
TTT TTT T
Generation 3 ------
TTTTT TT
TTT TT TT T T TTTT T TT
TTTT T T
# TTT TT# TTT T T T T T
TTT TTT T
Generation 4 ------
TTTTT TT
TTT TT TT T TT TTTT T TT
TTT# T T
TTT T# TTT T T T T T
TTT TTT T
Generation 5 ------
TTTTT TT
TTT TT TT T TT T### T TT
TT# T T
TTT # TTT T T T T T
TTT TTT T NIL </lang>
D
Textual Version
<lang d>import std.stdio, std.random, std.string, std.algorithm;
enum TREE_PROB = 0.55; // original tree probability enum F_PROB = 0.01; // auto combustion probability enum P_PROB = 0.01; // tree creation probability
enum Cell : char { empty=' ', tree='T', fire='#' } alias Cell[][] World;
bool hasBurningNeighbours(in World world, in int r, in int c) pure nothrow {
foreach (rowShift; -1 .. 2) foreach (colShift; -1 .. 2) if ((r + rowShift) >= 0 && (r + rowShift) < world.length && (c + colShift) >= 0 && (c + colShift) < world[0].length && world[r + rowShift][c + colShift] == Cell.fire) return true; return false;
}
void nextState(in World world, World nextWorld) {
foreach (r, row; world) foreach (c, elem; row) final switch (elem) { case Cell.empty: nextWorld[r][c]= uniform(0.,1.)<P_PROB?Cell.tree:Cell.empty; break;
case Cell.tree: if (world.hasBurningNeighbours(r, c)) nextWorld[r][c] = Cell.fire; else nextWorld[r][c]=uniform(0.,1.)<F_PROB?Cell.fire:Cell.tree; break;
case Cell.fire: nextWorld[r][c] = Cell.empty; break; }
}
void main() {
auto world = new World(8, 65); foreach (row; world) foreach (ref el; row) el = uniform(0.0, 1.0) < TREE_PROB ? Cell.tree : Cell.empty; auto nextWorld = new World(world.length, world[0].length);
foreach (i; 0 .. 4) { nextState(world, nextWorld); writeln(join(cast(string[])nextWorld, "\n"), "\n"); swap(world, nextWorld); }
}</lang>
- Output:
T T T#TT T TT TT TTTT TT TTT T TT T# T T TT TT TTTTT T TT TT T TTTTTTTTTT T TTT T T T TT TTTTTTTT TTTT #T TT T TTTTTT TTTTT TTT TTTT TTTT TTT T T T T T TT T TT T TT T TT T TT T TTTT T T TT TTT T TT T T T TT T TTT T TTTT T# T T T TTT TT TTTTT T T TT T T TT T TT TTTT TTT TTTTT T T T T TT T TTT T T T TT TTT T T T TTT T TT T TTT#TT T TT TTTTTTTT TTTT TTTTT TTTT TTT TT TTTTT TTTTTT TT TT T TT T TT T TT T TT TT TTTT TTTTT T T # #T T TT TT TTTT TT TTT T TT # T T TT TT TT### T TT TT # TTTTTTTTTT T TTT T T T ## TTTTTTTT TTTT # TT T TTTTTT TTTTT TTT TTTT TTTT TTT # T T T T TT T T# T TT T TT T TT T #TTT T T TT TTT T TT T T T TTT T TTT T TTTT # T T T TTT TT TTTTT T T TT T T TT T TT TTTT TTT T#### # T T T TT T TTT T T T TT TTT T T T TTT T TT T TT# #T T TT TTTTTTTT TTTT TTTTT TTTT TTT TT TTTTT TTTTTT TT ## T TT T TT T TT T TT TT TTTT TTTTT T T # T TT TT TTTT TT TTT T TT T T TT TT T# T TT TT TTTTTTTTTT T TTT T T T TTTTTTTT TTT# TT T T###TT TTT## TTT TTTT TTTT TT# T T T T #T T # T TT T TT T TT # #TT T T TT TTT T T# T T T TTT # TTT T TTTT # # T TTT TT TTTTT T T TT T T TT T TT TTTT TTT # T T # TT T TTT T T T TT TTT T T T TTT T TT # ## # T TT TTTTTTTT TTTT TTTTT TTTT TTT TT TTTTT TT#TTT TT T TT T TT T TT T TT TT TTTT TTTTT T T T TT TT TTTT TT TTT T TT T T TT TT # T TT T# TT####TTTT T TTT T T T TTTTTT## TT# TT T # #T ### TTT TTTT TTTT T# T T T T # T T TT T ## # TT ## T T TT TTT T # T T # #TT TTT T TTTT T ### TT TTTTT # T TT T T T# # TT TTTT TTT # T TT T TTT T T T TT TTT T T T TTT T ## T ## TTTTTTTT TTTT TTTTT TTTT TTT TT TTTTT T# #T# ## # TT T TT T TT T TT TT TTTT TTTTT
Graphical Version
(With Image class made final).
<lang d>import std.stdio, std.random, std.string, std.algorithm, simpledisplay;
enum double TREE_PROB = 0.55; // original tree probability enum double F_PROB = 0.01; // auto combustion probability enum double P_PROB = 0.01; // tree creation probability
template TypeTuple(T...) { alias T TypeTuple; } alias TypeTuple!(-1, 0, 1) sp;
enum Cell : char { empty=' ', tree='T', burning='#' } alias Cell[][] World;
immutable white = Color(255, 255, 255),
red = Color(255, 0, 0), green = Color(0, 255, 0);
void nextState(ref World world, ref World nextWorld,
ref Xorshift rnd, Image img) { enum double div = cast(double)typeof(rnd.front()).max; immutable nr = world.length; immutable nc = world[0].length; foreach (r, row; world) foreach (c, elem; row) final switch (elem) { case Cell.empty: img.putPixel(c, r, white); nextWorld[r][c] = (rnd.front()/div)<P_PROB ? Cell.tree : Cell.empty; rnd.popFront(); break;
case Cell.tree: img.putPixel(c, r, green);
foreach (rowShift; sp) foreach (colShift; sp) if ((r + rowShift) >= 0 && (r + rowShift) < nr && (c + colShift) >= 0 && (c + colShift) < nc && world[r + rowShift][c + colShift] == Cell.burning) { nextWorld[r][c] = Cell.burning; goto END; }
nextWorld[r][c]=(rnd.front()/div)<F_PROB ? Cell.burning : Cell.tree; rnd.popFront(); END: break;
case Cell.burning: img.putPixel(c, r, red); nextWorld[r][c] = Cell.empty; break; }
swap(world, nextWorld);
}
void main() {
auto rnd = Xorshift(1); auto world = new World(600, 600); // create world foreach (row; world) foreach (ref el; row) el = uniform(0.0, 1.0, rnd) < TREE_PROB ? Cell.tree : Cell.empty; auto nextWorld = new World(world.length, world[0].length);
auto w= new SimpleWindow(world.length,world[0].length,"ForestFire"); auto img = new Image(w.width, w.height);
w.eventLoop(1, { auto painter = w.draw(); nextState(world, nextWorld, rnd, img); painter.drawImage(Point(0, 0), img); });
}</lang> About 34 FPS, 600x600 cells.
F#
This implementation can be compiled or run in the interactive F# shell. <lang fsharp>open System open System.Diagnostics open System.Drawing open System.Drawing.Imaging open System.Runtime.InteropServices open System.Windows.Forms
module ForestFire =
type Cell = Empty | Tree | Fire
let rnd = new System.Random() let initial_factor = 0.35 let ignition_factor = 1e-5 // rate of lightning strikes (f) let growth_factor = 2e-3 // rate of regrowth (p) let width = 640 // width of the forest region let height = 480 // height of the forest region
let make_forest = Array2D.init height width (fun _ _ -> if rnd.NextDouble() < initial_factor then Tree else Empty) let count (forest:Cell[,]) row col = let mutable n = 0 let h,w = forest.GetLength 0, forest.GetLength 1 for r in row-1 .. row+1 do for c in col-1 .. col+1 do if r >= 0 && r < h && c >= 0 && c < w && forest.[r,c] = Fire then n <- n + 1 if forest.[row,col] = Fire then n-1 else n
let burn (forest:Cell[,]) r c = match forest.[r,c] with | Fire -> Empty | Tree -> if rnd.NextDouble() < ignition_factor then Fire else if (count forest r c) > 0 then Fire else Tree | Empty -> if rnd.NextDouble() < growth_factor then Tree else Empty
// All the functions below this point are drawing the generated images to screen. let make_image (pixels:int[]) = let bmp = new Bitmap(width, height) let bits = bmp.LockBits(Rectangle(0,0,width,height), ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb) Marshal.Copy(pixels, 0, bits.Scan0, bits.Height*bits.Width) |> ignore bmp.UnlockBits(bits) bmp
// This function is run asynchronously to avoid blocking the main GUI thread. let run (box:PictureBox) (label:Label) = async { let timer = new Stopwatch() let forest = make_forest |> ref let pixel = Array.create (height*width) (Color.Black.ToArgb()) let rec update gen = timer.Start() forest := burn !forest |> Array2D.init height width for y in 0..height-1 do for x in 0..width-1 do pixel.[x+y*width] <- match (!forest).[y,x] with | Empty -> Color.Gray.ToArgb() | Tree -> Color.Green.ToArgb() | Fire -> Color.Red.ToArgb() let img = make_image pixel box.Invoke(MethodInvoker(fun () -> box.Image <- img)) |> ignore let msg = sprintf "generation %d @ %.1f fps" gen (1000./timer.Elapsed.TotalMilliseconds) label.Invoke(MethodInvoker(fun () -> label.Text <- msg )) |> ignore timer.Reset() update (gen + 1) update 0 }
let main args = let form = new Form(AutoSize=true, Size=new Size(800,600), Text="Forest fire cellular automata") let box = new PictureBox(Dock=DockStyle.Fill,Location=new Point(0,0),SizeMode=PictureBoxSizeMode.StretchImage) let label = new Label(Dock=DockStyle.Bottom, Text="Ready") form.FormClosed.Add(fun eventArgs -> Async.CancelDefaultToken() Application.Exit()) form.Controls.Add(box) form.Controls.Add(label) run box label |> Async.Start form.Show() Application.Run() 0
- if INTERACTIVE
ForestFire.main [|""|]
- else
[<System.STAThread>] [<EntryPoint>] let main args = ForestFire.main args
- endif</lang>
Fortran
<lang fortran>module ForestFireModel
implicit none
type :: forestfire integer, dimension(:,:,:), allocatable :: field integer :: width, height integer :: swapu real :: prob_tree, prob_f, prob_p end type forestfire
integer, parameter :: & empty = 0, & tree = 1, & burning = 2
private :: bcheck, set, oget, burning_neighbor ! cset, get
contains
! create and initialize the field(s) function forestfire_new(w, h, pt, pf, pp) result(res) type(forestfire) :: res integer, intent(in) :: w, h real, intent(in), optional :: pt, pf, pp
integer :: i, j real :: r
allocate(res%field(2,w,h)) ! no error check res%prob_tree = 0.5 res%prob_f = 0.00001 res%prob_p = 0.001 if ( present(pt) ) res%prob_tree = pt if ( present(pf) ) res%prob_f = pf if ( present(pp) ) res%prob_p = pp
res%width = w res%height = h res%swapu = 0
res%field = empty
do i = 1,w do j = 1,h call random_number(r) if ( r <= res%prob_tree ) call cset(res, i, j, tree) end do end do end function forestfire_new ! destroy the field(s) subroutine forestfire_destroy(f) type(forestfire), intent(inout) :: f
if ( allocated(f%field) ) deallocate(f%field) end subroutine forestfire_destroy
! evolution subroutine forestfire_evolve(f) type(forestfire), intent(inout) :: f
integer :: i, j real :: r
do i = 1, f%width do j = 1, f%height select case ( get(f, i, j) ) case (burning) call set(f, i, j, empty) case (empty) call random_number(r) if ( r > f%prob_p ) then call set(f, i, j, empty) else call set(f, i, j, tree) end if case (tree) if ( burning_neighbor(f, i, j) ) then call set(f, i, j, burning) else call random_number(r) if ( r > f%prob_f ) then call set(f, i, j, tree) else call set(f, i, j, burning) end if end if end select end do end do f%swapu = ieor(f%swapu, 1) end subroutine forestfire_evolve
! helper funcs/subs subroutine set(f, i, j, t) type(forestfire), intent(inout) :: f integer, intent(in) :: i, j, t
if ( bcheck(f, i, j) ) then f%field(ieor(f%swapu,1), i, j) = t end if end subroutine set
subroutine cset(f, i, j, t) type(forestfire), intent(inout) :: f integer, intent(in) :: i, j, t
if ( bcheck(f, i, j) ) then f%field(f%swapu, i, j) = t end if end subroutine cset
function bcheck(f, i, j) logical :: bcheck type(forestfire), intent(in) :: f integer, intent(in) :: i, j bcheck = .false. if ( (i >= 1) .and. (i <= f%width) .and. & (j >= 1) .and. (j <= f%height) ) bcheck = .true. end function bcheck
function get(f, i, j) result(r) integer :: r type(forestfire), intent(in) :: f integer, intent(in) :: i, j if ( .not. bcheck(f, i, j) ) then r = empty else r = f%field(f%swapu, i, j) end if end function get
function oget(f, i, j) result(r) integer :: r type(forestfire), intent(in) :: f integer, intent(in) :: i, j if ( .not. bcheck(f, i, j) ) then r = empty else r = f%field(ieor(f%swapu,1), i, j) end if end function oget
function burning_neighbor(f, i, j) result(r) logical :: r type(forestfire), intent(in) :: f integer, intent(in) :: i, j
integer, dimension(3,3) :: s s = f%field(f%swapu, i-1:i+1, j-1:j+1) s(2,2) = empty r = any(s == burning) end function burning_neighbor
subroutine forestfire_print(f) type(forestfire), intent(in) :: f
integer :: i, j
do j = 1, f%height do i = 1, f%width select case(get(f, i, j)) case (empty) write(*,'(A)', advance='no') '.' case (tree) write(*,'(A)', advance='no') 'Y' case (burning) write(*,'(A)', advance='no') '*' end select end do write(*,*) end do end subroutine forestfire_print
end module ForestFireModel</lang>
<lang fortran>program ForestFireTest
use ForestFireModel implicit none
type(forestfire) :: f integer :: i
f = forestfire_new(74, 40)
do i = 1, 1001 write(*,'(A)', advance='no') achar(z'1b') // '[H' // achar(z'1b') // '[2J' call forestfire_print(f) call forestfire_evolve(f) end do call forestfire_destroy(f)
end program ForestFireTest</lang>
Go
Text. The program prints the configuration, waits for the Enter key, and prints the next. It makes a pretty good animation to just hold down the Enter key. <lang go>package main
import (
"fmt" "math/rand" "strings"
)
const (
rows = 20 cols = 30 p = .01 f = .001
)
const rx = rows + 2 const cx = cols + 2
func main() {
odd := make([]byte, rx*cx) even := make([]byte, rx*cx) for r := 1; r <= rows; r++ { for c := 1; c <= cols; c++ { if rand.Intn(2) == 1 { odd[r*cx+c] = 'T' } } } for { print(odd) step(even, odd) fmt.Scanln()
print(even) step(odd, even) fmt.Scanln() }
}
func print(model []byte) {
fmt.Println(strings.Repeat("__", cols)) fmt.Println() for r := 1; r <= rows; r++ { for c := 1; c <= cols; c++ { if model[r*cx+c] == 0 { fmt.Print(" ") } else { fmt.Printf(" %c", model[r*cx+c]) } } fmt.Println() }
}
func step(dst, src []byte) {
for r := 1; r <= rows; r++ { for c := 1; c <= cols; c++ { x := r*cx + c dst[x] = src[x] switch dst[x] { case '#': // rule 1. A burning cell turns into an empty cell dst[x] = 0 case 'T': // rule 2. A tree will burn if at least one neighbor is burning if src[x-cx-1]=='#' || src[x-cx]=='#' || src[x-cx+1]=='#' || src[x-1] == '#' || src[x+1] == '#' || src[x+cx-1]=='#' || src[x+cx]=='#' || src[x+cx+1] == '#' { dst[x] = '#'
// rule 3. A tree ignites with probability f // even if no neighbor is burning } else if rand.Float64() < f { dst[x] = '#' } default: // rule 4. An empty space fills with a tree with probability p if rand.Float64() < p { dst[x] = 'T' } } } }
}</lang>
Haskell
<lang haskell>import Data.List import Control.Arrow import Control.Monad import System.Random
data Cell = Empty | Tree | Fire deriving (Eq)
instance Show Cell where
show Empty = " " show Tree = "T" show Fire = "$"
randomCell = liftM ([Empty, Tree] !!) (randomRIO (0,1) :: IO Int) randomChance = randomRIO (0,1.0) :: IO Double
rim b = map (fb b). (fb =<< rb) where
fb = liftM2 (.) (:) (flip (++) . return) rb = fst. unzip. zip (repeat b). head
take3x3 = concatMap (transpose. map take3). take3 where
take3 = init. init. takeWhile (not.null). map(take 3). tails
list2Mat n = takeWhile(not.null). map(take n). iterate(drop n)
evolveForest :: Int -> Int -> Int -> IO () evolveForest m n k = do
let s = m*n fs <- replicateM s randomCell
let nextState xs = do ts <- replicateM s randomChance vs <- replicateM s randomChance let rv [r1,[l,c,r],r3] newTree fire | c == Fire = Empty | c == Tree && Fire `elem` concat [r1,[l,r],r3] = Fire | c == Tree && 0.01 >= fire = Fire | c == Empty && 0.1 >= newTree = Tree | otherwise = c return $ zipWith3 rv xs ts vs
evolve i xs = unless (i > k) $ do let nfs = nextState $ take3x3 $ rim Empty $ list2Mat n xs putStrLn ("\n>>>>>> " ++ show i ++ ":") mapM_ (putStrLn. concatMap show) $ list2Mat n xs nfs >>= evolve (i+1)
evolve 1 fs</lang>
A run: <lang haskell>*Main> evolveForest 6 50 3
>>>>>> 1:
T T T TTTTTTTTT TT TT T T T TT TT TTT TT T TT TTTT T T TT T T T T T T TTTTT T T TT T TTT T TTTTT TTTTTTTT T TTT TTTT TT TT TT T TT T TTT T T T TTTT T TTT TT T TT TT TT TT TT T T T T TT T T TT T T TTTTT T TT T T T TTTTTT T T T T T TT T TT
>>>>>> 2:
T T T TTTTTTTTT TT TT TT T $ TT TT TTT TT T TT TTTT T T TT T T T T T T TTTTT T TT TTTT TT$ T TTTTTT TTTTT$TT T T$T TTTT TT TT TT T TT T TTTTTTT T TTTT T TTT TT T TT TT TT TT TT T T T T TT T T TT T T TTTTT
TTT TT TT T T TTTTTT T T T T T TT TT TT
>>>>>> 3:
TTTTT T TTTTTTTTT TT TT TT T TT TT TTTT TT T $$ TTTT T T $$ T T T T $ $ TTTTT T TTTTTTT T$ T TTTTTT TTTT$ $T T $ $ TTTTT TT TT TT T $$ T TTTTTTT T $$$T T TTT $$ T T TTT TT TT TT TTT T T TT TT TT T T TT T T TTTTT
TTT TT TT T T T TTTTTT T T T T T TT TT TT</lang>
Icon and Unicon
<lang Icon>link graphics,printf
$define EDGE 0 $define EMPTY 1 $define TREE 2 $define FIRE 3
global Colours,Width,Height,ProbTree,ProbFire,ProbInitialTree,Forest,oldForest
procedure main() # forest fire
Height := 400 # Window height Width := 400 # Window width ProbInitialTree := .10 # intial probability of trees ProbTree := .01 # ongoing probability of trees ProbFire := ProbTree/50. # probability of fire Rounds := 500 # rounds to evolve setup_forest() every 1 to Rounds do { show_forest() evolve_forest() } printf("Forest fire %d x %d rounds=%d p.initial=%r p/f=%r/%r fps=%r\n", Width,Height,Rounds,ProbInitialTree,ProbTree,ProbFire, Rounds/(&time/1000.)) # stats WDone()
end
procedure setup_forest() #: setup the forest
Colours := table() # define colours Colours[EDGE] := "black" Colours[EMPTY] := "grey" Colours[TREE] := "green" Colours[FIRE] := "red" WOpen("label=Forest Fire", "bg=black", "size=" || Width+2 || "," || Height+2) | # add for border stop("Unable to open Window") every !(Forest := list(Height)) := list(Width,EMPTY) # default every ( Forest[1,1 to Width] | Forest[Height,1 to Width] | Forest[1 to Height,1] | Forest[1 to Height,Width] ) := EDGE every r := 2 to Height-1 & c := 2 to Width-1 do if probability(ProbInitialTree) then Forest[r,c] := TREE
end
procedure show_forest() #: show Forest - drawn changes only
every r := 2 to *Forest-1 & c := 2 to *Forest[r]-1 do if /oldForest | oldForest[r,c] ~= Forest[r,c] then { WAttrib("fg=" || Colours[Forest[r,c]]) DrawPoint(r,c) }
end
procedure evolve_forest() #: evolve forest
old := oldForest := list(*Forest) # freeze copy every old[i := 1 to *Forest] := copy(Forest[i]) # deep copy
every r := 2 to *Forest-1 & c := 2 to *Forest[r]-1 do Forest[r,c] := case old[r,c] of { # apply rules FIRE : EMPTY TREE : if probability(ProbFire) | ( old[r-1, c-1 to c+1] | old[r,c-1|c+1] | old[r+1,c-1 to c+1] ) = FIRE then FIRE EMPTY: if probability(ProbTree) then TREE }
end
procedure probability(P) #: succeed with probability P if ?0 <= P then return end</lang>
J
<lang j>NB. states: 0 empty, 1 tree, _1 fire dims =:10 10
tessellate=: 0,0,~0,.0,.~ 3 3 >./@,;._3 ] mask=: tessellate dims$1 chance=: 1 :'(> ? bind (dims$0)) bind (mask*m)'
start=: 0.5 chance grow =: 0.01 chance fire =: 0.001 chance
spread=: [: tessellate 0&>
step=: grow [`]@.(|@])"0 >.&0 * _1 ^ fire +. spread
run=:3 :0 forest=. start for.i.y do. smoutput ' #o' {~ forest=. step forest end. )</lang>
Example use:
<lang j> run 2
##### # # # ### #### # # # # ##### # ## # # # # o## # ##### # # # ### #### # # # # ##### # ## # # o # o# # </lang>
Note that I have used an artificially small grid here, and that I ran this several times until I could find one that had a fire from the start. Also, the current revision of this code does not show the starting state, though that would be easily changed.
Also, currently the parameters defining the size of the forest, and the probabilities are hard coded into the program and you need to rerun the program's script when they change.
Finally note that the grid size includes the one cell "border" which are blank. If the border cells are meant to be outside of the represented dimensions, you can add 2 to them (or change the code to do so).
Java
Text
<lang java5>import java.util.Arrays; import java.util.LinkedList; import java.util.List;
public class Fire { private static final char BURNING = 'w'; //w looks like fire, right? private static final char TREE = 'T'; private static final char EMPTY = '.'; private static final double F = 0.2; private static final double P = 0.4; private static final double TREE_PROB = 0.5;
private static List<String> process(List<String> land){ List<String> newLand = new LinkedList<String>(); for(int i = 0; i < land.size(); i++){ String rowAbove, thisRow = land.get(i), rowBelow; if(i == 0){//first row rowAbove = null; rowBelow = land.get(i + 1); }else if(i == land.size() - 1){//last row rowBelow = null; rowAbove = land.get(i - 1); }else{//middle rowBelow = land.get(i + 1); rowAbove = land.get(i - 1); } newLand.add(processRows(rowAbove, thisRow, rowBelow)); } return newLand; }
private static String processRows(String rowAbove, String thisRow, String rowBelow){ String newRow = ""; for(int i = 0; i < thisRow.length();i++){ switch(thisRow.charAt(i)){ case BURNING: newRow+= EMPTY; break; case EMPTY: newRow+= Math.random() < P ? TREE : EMPTY; break; case TREE: String neighbors = ""; if(i == 0){//first char neighbors+= rowAbove == null ? "" : rowAbove.substring(i, i + 2); neighbors+= thisRow.charAt(i + 1); neighbors+= rowBelow == null ? "" : rowBelow.substring(i, i + 2); if(neighbors.contains(Character.toString(BURNING))){ newRow+= BURNING; break; } }else if(i == thisRow.length() - 1){//last char neighbors+= rowAbove == null ? "" : rowAbove.substring(i - 1, i + 1); neighbors+= thisRow.charAt(i - 1); neighbors+= rowBelow == null ? "" : rowBelow.substring(i - 1, i + 1); if(neighbors.contains(Character.toString(BURNING))){ newRow+= BURNING; break; } }else{//middle neighbors+= rowAbove == null ? "" : rowAbove.substring(i - 1, i + 2); neighbors+= thisRow.charAt(i + 1); neighbors+= thisRow.charAt(i - 1); neighbors+= rowBelow == null ? "" : rowBelow.substring(i - 1, i + 2); if(neighbors.contains(Character.toString(BURNING))){ newRow+= BURNING; break; } } newRow+= Math.random() < F ? BURNING : TREE; } } return newRow; }
public static List<String> populate(int width, int height){ List<String> land = new LinkedList<String>(); for(;height > 0; height--){//height is just a copy anyway StringBuilder line = new StringBuilder(width); for(int i = width; i > 0; i--){ line.append((Math.random() < TREE_PROB) ? TREE : EMPTY); } land.add(line.toString()); } return land; }
//process the land n times public static void processN(List<String> land, int n){ for(int i = 0;i < n; i++){ land = process(land); } }
//process the land n times and print each step along the way public static void processNPrint(List<String> land, int n){ for(int i = 0;i < n; i++){ land = process(land); print(land); } }
//print the land public static void print(List<String> land){ for(String row: land){ System.out.println(row); } System.out.println(); }
public static void main(String[] args){ List<String> land = Arrays.asList(".TTT.T.T.TTTT.T", "T.T.T.TT..T.T..", "TT.TTTT...T.TT.", "TTT..TTTTT.T..T", ".T.TTT....TT.TT", "...T..TTT.TT.T.", ".TT.TT...TT..TT", ".TT.T.T..T.T.T.", "..TTT.TT.T..T..", ".T....T.....TTT", "T..TTT..T..T...", "TTT....TTTTTT.T", "......TwTTT...T", "..T....TTTTTTTT", ".T.T.T....TT..."); print(land); processNPrint(land, 10);
System.out.println("Random land test:");
land = populate(10, 10); print(land); processNPrint(land, 10); } }</lang>
Graphics
JAMES II/Rule-based Cellular Automata
<lang j2carules>@caversion 1;
dimensions 2;
state EMPTY, TREE, BURNING;
// an empty cell grows a tree with a chance of p = 5 % rule{EMPTY} [0.05] : -> TREE;
// a burning cell turns to a burned cell rule{BURNING}: -> EMPTY;
// a tree starts burning if there is at least one neighbor burning rule{TREE} : BURNING{1,} -> BURNING;
// a tree is hit by lightning with a change of f = 0.006 % rule{TREE} [0.00006] : -> BURNING;</lang> The starting configuration cannot be given in the modeling language since the concepts of the model and its parameters (which includes the starting configuration) are separate in JAMES II.
JavaScript
<lang javascript>var forest = {
X: 50, Y: 50, propTree: 0.5, propTree2: 0.01, propBurn: 0.0001, t: [], c: ['rgb(255,255,255)', 'rgb(0,255,0)', 'rgb(255,0,0)']
};
for(var i = 0; i < forest.Y; i++) {
forest.t[i] = []; for(var j = 0; j < forest.Y; j++) { forest.t[i][j] = Math.random() < forest.propTree ? 1 : 0; }
}
function afterLoad(forest) {
var canvas = document.getElementById('canvas'); var c = canvas.getContext('2d'); for(var i = 0; i < forest.X; i++) { for(var j = 0; j < forest.Y; j++) { c.fillStyle = forest.c[forest.t[i][j]]; c.fillRect(10*j, 10*i, 10*j+9, 10*i+9); } }
}
function doStep(forest) {
var to = []; for(var i = 0; i < forest.Y; i++) { to[i] = forest.t[i].slice(0); }
//indices outside the array are undefined; which converts to 0=empty on forced typecast for(var i = 0; i < forest.Y; i++) { for(var j = 0; j < forest.Y; j++) { if(0 == to[i][j]) { forest.t[i][j] = Math.random() < forest.propTree2 ? 1 : 0; } else if(1 == to[i][j]) { if( ((i>0) && (2 == to[i-1][j])) || ((i<forest.Y-1) && (2 == to[i+1][j])) || ((j>0) && (2 == to[i][j-1])) || ((j<forest.X-1) && (2 == to[i][j+1])) ) { forest.t[i][j] = 2; } else { forest.t[i][j] = Math.random() < forest.propBurn ? 2 : 1; } } else if(2 == to[i][j]) { //If it burns, it gets empty ... forest.t[i][j] = 0; } } }
}
window.setInterval(function(){
doStep(forest); afterLoad(forest);
}, 100); </lang>
To actually see it work we need a small demo page with HTML5 compliant code:
<lang html5><!DOCTYPE html> <html> <head> <title>Forest Fire</title> </head> <body> <canvas id="canvas" width="500" height="500"> Your browser doesn't support HTML5 Canvas. </canvas> <script language="JavaScript">//<![CDATA[ HERE COMES THE SCRIPT FROM ABOVE <-- //-->]]></script> </body> </html> </lang>
The output is a (mostly fluent) animation of the area.
Liberty BASIC
<lang lb>'[RC] Forest Fire
dim oldgen(200,200), newgen(200,200) p =0.99 f =0.9999
nomainwin WindowWidth = 200 WindowHeight = 200 open "Forest Fire" for graphics_nsb_nf as #1 #1 "trapclose [quit]" #1 "down ; fill brown ; flush"
p =0.99 f =0.9999
for generation = 1 to 200 for x = 1 to 199 for y = 1 to 199 scan 'we can break early select case oldgen(x,y) case 0 if rnd(0) > p then newgen(x,y) = 1 : #1 "color green ; set "; x; " "; y case 2 newgen(x,y) = 0 : #1 "color brown ; set "; x; " "; y case 1 if oldgen(x-1,y-1) = 2 or oldgen(x-1,y) = 2 or oldgen(x-1,y+1) = 2_ or oldgen(x,y-1) = 2 or oldgen(x,y+1) = 2 or oldgen(x+1,y-1) = 2_ or oldgen(x+1,y) = 2 or oldgen(x+1,y+1) = 2 or rnd(0) > f then #1 "color red ; set "; x; " "; y newgen(x,y) = 2 end if end select oldgen(x-1,y-1)=newgen(x-1,y-1) next y next x next generation
[quit] close #1 end</lang>
Mathematica
Mathematica is good at working with cellular automata -- especially 2-color 1-dimensional cellular automata. The automaton function is awkward yet very powerful. This code implements a 3-color 2-dimensional cellular automaton with 9-cell neighbourhoods using a custom cell evolution function. There is probably a rule number specification that can replace the custom evolution function and make this simpler and faster. But this works well enough. The last line of code plots the state of the forest after the 300th step.
<lang Mathematica>evolve[nbhd_List, k_] := 0 /; nbhd2, 2 == 2 (*burning->empty*) evolve[nbhd_List, k_] := 2 /; nbhd2, 2 == 1 && Max@nbhd == 2 (*near_burning&nonempty->burning*) evolve[nbhd_List, k_] := RandomChoice[{f, 1 - f} -> {2, nbhd2, 2}] /; nbhd2, 2 == 1 && Max@nbhd < 2 (*spontaneously combusting tree*) evolve[nbhd_List, k_] := RandomChoice[{p, 1 - p} -> {1, nbhd2, 2}] /; nbhd2, 2 == 0 (*random tree growth*)
r = 100; c = 100; p = 10^-2; f = 10^-4; init = RandomInteger[BernoulliDistribution[0.05], {r, c}]; MatrixPlot[CellularAutomaton[{evolve, {}, {1, 1}}, {init, 0}, {{{300}}}], ColorRules -> {0 -> White, 1 -> Green, 2 -> Red}, Frame -> False]</lang>
OCaml
This example uses a curses display (with the ocaml-curses bindings).
<lang ocaml>open Curses
let ignite_prob = 0.02 let sprout_prob = 0.01
type cell = Empty | Burning | Tree
let get w x y =
try w.(x).(y) with Invalid_argument _ -> Empty
let neighborhood_burning w x y =
try for _x = pred x to succ x do for _y = pred y to succ y do if get w _x _y = Burning then raise Exit done done ; false with Exit -> true
let evolves w x y =
match w.(x).(y) with | Burning -> Empty | Tree -> if neighborhood_burning w x y then Burning else begin if (Random.float 1.0) < ignite_prob then Burning else Tree end | Empty -> if (Random.float 1.0) < sprout_prob then Tree else Empty
let step width height w =
for x = 0 to pred width do for y = 0 to pred height do w.(x).(y) <- evolves w x y done done
let i = int_of_char let repr = function
| Empty -> i ' ' | Burning -> i '#' | Tree -> i 't'
let draw width height w =
for x = 0 to pred width do for y = 0 to pred height do ignore(move y x); ignore(delch ()); ignore(insch (repr w.(x).(y))); done; done; ignore(refresh ())
let () =
Random.self_init (); let wnd = initscr () in ignore(cbreak ()); ignore(noecho ()); let height, width = getmaxyx wnd in let w = Array.make_matrix width height Empty in clear (); ignore(refresh ()); while true do draw width height w; step width height w; Unix.sleep 1; done; endwin()</lang>
You can execute this script with:
$ ocaml unix.cma -I +curses curses.cma forest.ml
Perl
Requires terminal that understands ANSI escape sequences:<lang Perl> use 5.10.0;
my $w = `tput cols` - 1; my $h = `tput lines` - 1; my $r = "\033[H";
my ($green, $red, $yellow, $norm) = ("\033[32m", "\033[31m", "\033[33m", "\033[m");
my $tree_prob = .05; my $burn_prob = .0002;
my @forest = map([ map((rand(1) < $tree_prob) ? 1 : 0, 1 .. $w) ], 1 .. $h);
sub iterate { my @new = map([ map(0, 1 .. $w) ], 1 .. $h); for my $i (0 .. $h - 1) { for my $j (0 .. $w - 1) { $new[$i][$j] = $forest[$i][$j]; if ($forest[$i][$j] == 2) { $new[$i][$j] = 3; next; } elsif ($forest[$i][$j] == 1) { if (rand() < $burn_prob) { $new[$i][$j] = 2; next; } for ( [-1, -1], [-1, 0], [-1, 1], [ 0, -1], [ 0, 1], [ 1, -1], [ 1, 0], [ 1, 1] ) { my $y = $_->[0] + $i; next if $y < 0 || $y >= $h; my $x = $_->[1] + $j; next if $x < 0 || $x >= $w; if ($forest[$y][$x] == 2) { $new[$i][$j] = 2; last; } } } elsif (rand() < $tree_prob) { $new[$i][$j] = 1; } elsif ($forest[$i][$j] == 3) { $new[$i][$j] = 0; } }} @forest = @new; }
sub forest { print $r; for (@forest) { for (@$_) { when(0) { print " "; } when(1) { print "${green}*"} when(2) { print "${red}&" } when(3) { print "${yellow}&" } } print "\033[E\033[1G"; } iterate; }
forest while (1);</lang>
Perl 6
<lang perl6>my $RED = "\e[1;31m"; my $CLEAR = "\e[0m";
enum Cell-State <Empty Tree Burning>; my @show = (' ', '木', $RED ~ '木' ~ $CLEAR);
class Forest {
has Cell-State @!grid; has @!neighbors; has Int $.height; has Int $.width; has $.p; has $.f; method new(Int $height, Int $width, $p=0.01, $f=0.001) { my $c = self.bless(*, :$height, :$width, :$p, :$f); $c!init-grid; $c!init-neighbors; return $c; } method !init-grid {
@!grid = [ (Bool.pick ?? Tree !! Empty) xx $!width ] xx $!height;
} method !init-neighbors { for ^$!height X ^$!width -> $i, $j { @!neighbors[$i][$j] = gather for [-1,-1],[+0,-1],[+1,-1], [-1,+0],( ),[+1,+0], [-1,+1],[+0,+1],[+1,+1]
{ take-rw @!grid[$i + .[0]][$j + .[1]] // next; }
} } method step { my @new; for ^$!height X ^$!width -> $i, $j { given @!grid[$i][$j] { when Empty { @new[$i][$j] = rand < $!p ?? Tree !! Empty } when Tree { @new[$i][$j] = (@!neighbors[$i][$j].any === Burning or rand < $!f) ?? Burning !! Tree; } when Burning { @new[$i][$j] = Empty } } } for ^$!height X ^$!width -> $i, $j { @!grid[$i][$j] = @new[$i][$j]; } } method Str { join , gather for ^$!height -> $i { take @show[@!grid[$i].list], "\n"; } }
}
my Forest $f .= new(20,30); print "\e[2J"; # ANSI clear screen
my $i = 0; loop {
print "\e[H"; # ANSI home say $i++; say $f.Str; $f.step;
}</lang>
PicoLisp
<lang PicoLisp>(load "@lib/simul.l")
(scl 3)
(de forestFire (Dim ProbT ProbP ProbF)
(let Grid (grid Dim Dim) (for Col Grid (for This Col (=: tree (> ProbT (rand 0 1.0))) ) ) (loop (disp Grid NIL '((This) (cond ((: burn) "# ") ((: tree) "T ") (T ". ") ) ) ) (wait 1000) (for Col Grid (for This Col (=: next (cond ((: burn) NIL) ((: tree) (if (or (find # Neighbor burning? '((Dir) (get (Dir This) 'burn)) (quote west east south north ((X) (south (west X))) ((X) (north (west X))) ((X) (south (east X))) ((X) (north (east X))) ) ) (> ProbF (rand 0 1.0)) ) 'burn 'tree ) ) (T (and (> ProbP (rand 0 1.0)) 'tree)) ) ) ) ) (for Col Grid (for This Col (if (: next) (put This @ T) (=: burn) (=: tree) ) ) ) ) ) )</lang>
Use:
(forestFire 26 0.5 0.01 0.001)
PostScript
<lang PostScript>%!PS-Adobe-3.0 %%BoundingBox: 0 0 400 400
/size 400 def
/rand1 { rand 2147483647 div } def
/m { moveto } bind def /l { rlineto} bind def /drawforest {
0 1 n 1 sub { /y exch def 0 1 n 1 sub { /x exch def forest x get y get dup 0 eq { pop } { 1 eq { 0 1 0 } { 1 0 0 } ifelse setrgbcolor x c mul y c mul m c 0 l 0 c l c neg 0 l closepath fill } ifelse } for } for
} def
/r1n { dup 0 ge exch n lt and } def
/neighbors { /y exch def /x exch def /cnt 0 def
[ y 1 sub 1 y 1 add { /y1 exch def y1 r1n { x 1 sub 1 x 1 add { /x1 exch def x1 r1n { forest x1 get y1 get } if } for } if } for]
} def
/iter {
/nf [ n {[ n {0} repeat]} repeat ] def 0 1 n 1 sub { /x exch def 0 1 n 1 sub { /y exch def nf x get y forest x get y get dup 0 eq { pop rand1 treeprob le {1}{0} ifelse } { 1 eq { /fire false def x y neighbors { -1 eq { /fire true def } if } forall fire {-1}{ rand1 burnprob lt {-1}{1} ifelse } ifelse }{0} ifelse } ifelse put } for } for /forest nf def
} def
/n 200 def /treeprob .05 def /burnprob .0001 def /c size n div def /forest [ n {[ n { rand1 treeprob le {1}{0} ifelse } repeat]} repeat ] def
1000 { drawforest showpage iter } repeat %%EOF</lang>
PureBasic
<lang PureBasic>; Some systems reports high CPU-load while running this code.
- This may likely be due to the graphic driver used in the
- 2D-function Plot().
- If experiencing this problem, please reduce the #Width & #Height
- or activate the parameter #UnLoadCPU below with a parameter 1 or 2.
- This code should work with the demo version of PureBasic on both PC & Linux
- General parameters for the world
- f = 1e-6
- p = 1e-2
- SeedATree = 0.005
- Width = 400
- Height = 400
- Setting up colours
- Fire = $080CF7
- BackGround = $BFD5D3
- YoungTree = $00E300
- NormalTree = $00AC00
- MatureTree = $009500
- OldTree = $007600
- Black = $000000
- Depending on your hardware, use this to control the speed/CPU-load.
- 0 = No load reduction
- 1 = Only active about every second frame
- 2 = '1' & release the CPU after each horizontal line.
- UnLoadCPU = 0
Enumeration
#Empty =0 #Ignited #Burning #Tree #Old=#Tree+20
EndEnumeration
Global Dim Forest.i(#Width, #Height) Global Title$="Forest fire in PureBasic" Global Cnt
Macro Rnd()
(Random(2147483647)/2147483647.0)
EndMacro
Procedure Limit(n, min, max)
If n<min n=min ElseIf n>max n=max EndIf ProcedureReturn n
EndProcedure
Procedure SpreadFire(x,y)
Protected cnt=0, i, j For i=Limit(x-1, 0, #Width) To Limit(x+1, 0, #Width) For j=Limit(y-1, 0, #Height) To Limit(y+1, 0, #Height) If Forest(i,j)>=#Tree Forest(i,j)=#Ignited EndIf Next Next
EndProcedure
Procedure InitMap()
Protected x, y, type For y=1 To #Height For x=1 To #Width If Rnd()<=#SeedATree type=#Tree Else type=#Empty EndIf Forest(x,y)=type Next Next
EndProcedure
Procedure UpdateMap()
Protected x, y For y=1 To #Height For x=1 To #Width Select Forest(x,y) Case #Burning Forest(x,y)=#Empty SpreadFire(x,y) Case #Ignited Forest(x,y)=#Burning Case #Empty If Rnd()<=#p Forest(x,y)=#Tree EndIf Default If Rnd()<=#f Forest(x,y)=#Burning Else Forest(x,y)+1 EndIf EndSelect Next Next
EndProcedure
Procedure PresentMap()
Protected x, y, c cnt+1 SetWindowTitle(0,Title$+", time frame="+Str(cnt)) StartDrawing(ImageOutput(1)) For y=0 To OutputHeight()-1 For x=0 To OutputWidth()-1 Select Forest(x,y) Case #Empty c=#BackGround Case #Burning, #Ignited c=#Fire Default If Forest(x,y)<#Tree+#Old c=#YoungTree ElseIf Forest(x,y)<#Tree+2*#Old c=#NormalTree ElseIf Forest(x,y)<#Tree+3*#Old c=#MatureTree ElseIf Forest(x,y)<#Tree+4*#Old c=#OldTree Else ; Tree died of old age Forest(x,y)=#Empty c=#Black EndIf EndSelect Plot(x,y,c) Next CompilerIf #UnLoadCPU>1 Delay(1) CompilerEndIf Next StopDrawing() ImageGadget(1, 0, 0, #Width, #Height, ImageID(1))
EndProcedure
If OpenWindow(0, 10, 30, #Width, #Height, Title$, #PB_Window_MinimizeGadget)
SmartWindowRefresh(0, 1) If CreateImage(1, #Width, #Height) Define Event, freq If ExamineDesktops() And DesktopFrequency(0) freq=DesktopFrequency(0) Else freq=60 EndIf AddWindowTimer(0,0,5000/freq) InitMap() Repeat Event = WaitWindowEvent() Select Event Case #PB_Event_CloseWindow End Case #PB_Event_Timer CompilerIf #UnLoadCPU>0 Delay(25) CompilerEndIf UpdateMap() PresentMap() EndSelect ForEver EndIf
Python
Just hit return to advance the simulation, or enter an integer to advance that integer amount of 'frames'. Entering 'p' will print the grid, and 'q' will quit. A summary of the grids status is printed before each prompt for input. <lang python> Forest-Fire Cellular automation
See: http://en.wikipedia.org/wiki/Forest-fire_model
L = 15
- d = 2 # Fixed
initial_trees = 0.55 p = 0.01 f = 0.001
try:
raw_input
except:
raw_input = input
import random
tree, burning, space = 'TB.'
hood = ((-1,-1), (-1,0), (-1,1),
(0,-1), (0, 1), (1,-1), (1,0), (1,1))
def initialise():
grid = {(x,y): (tree if random.random()<= initial_trees else space) for x in range(L) for y in range(L) } return grid
def gprint(grid):
txt = '\n'.join(.join(grid[(x,y)] for x in range(L)) for y in range(L)) print(txt)
def quickprint(grid):
t = b = 0 ll = L * L for x in range(L): for y in range(L): if grid[(x,y)] in (tree, burning): t += 1 if grid[(x,y)] == burning: b += 1 print(('Of %6i cells, %6i are trees of which %6i are currently burning.' + ' (%6.3f%%, %6.3f%%)') % (ll, t, b, 100. * t / ll, 100. * b / ll))
def gnew(grid):
newgrid = {} for x in range(L): for y in range(L): if grid[(x,y)] == burning: newgrid[(x,y)] = space elif grid[(x,y)] == space: newgrid[(x,y)] = tree if random.random()<= p else space elif grid[(x,y)] == tree: newgrid[(x,y)] = (burning if any(grid.get((x+dx,y+dy),space) == burning for dx,dy in hood) or random.random()<= f else tree) return newgrid
if __name__ == '__main__':
grid = initialise() iter = 0 while True: quickprint(grid) inp = raw_input('Print/Quit/<int>/<return> %6i: ' % iter).lower().strip() if inp: if inp[0] == 'p': gprint(grid) elif inp.isdigit(): for i in range(int(inp)): iter +=1 grid = gnew(grid) quickprint(grid) elif inp[0] == 'q': break grid = gnew(grid) iter +=1</lang>
Sample output
Of 225 cells, 108 are trees of which 0 are currently burning. (48.000%, 0.000%) Print/Quit/<int>/<return> 0: Of 225 cells, 114 are trees of which 1 are currently burning. (50.667%, 0.444%) Print/Quit/<int>/<return> 1: p .TTT.T.T.TTTT.T T.T.T.TT..T.T.. TT.TTTT...T.TT. TTT..TTTTT.T..T .T.TTT....TT.TT ...T..TTT.TT.T. .TT.TT...TT..TT .TT.T.T..T.T.T. ..TTT.TT.T..T.. .T....T.....TTT T..TTT..T..T... TTT....TTTTTT.T ......TBTTT...T ..T....TTTTTTTT .T.T.T....TT... Of 225 cells, 115 are trees of which 6 are currently burning. (51.111%, 2.667%) Print/Quit/<int>/<return> 2: p .TTT.TTT.TTTT.T T.T.T.TT..T.T.. TT.TTTT...T.TT. TTT..TTTTT.T..T .T.TTT....TT.TT ...T..TTT.TT.T. .TT.TT...TT..TT .TT.T.T..T.T.T. ..TTT.TT.T..T.. .T....T.....TTT T..TTT..T..T... TTT....BBTTTT.T ....T.B.BTT...T ..T....BBTTTTTT .T.T.T....TT... Of 225 cells, 113 are trees of which 4 are currently burning. (50.222%, 1.778%) Print/Quit/<int>/<return> 3: p .TTT.TTT.TTTT.T T.T.T.TT..T.T.. TT.TTTT...T.TT. TTT..TTTTT.T..T .T.TTT...TTT.TT ...T..TTT.TTTTT .TT.TT...TT..TT .TT.T.T..T.T.T. ..TTT.TT.T..T.. .T.T..T.....TTT T..TTT..B..T... TTT......BTTT.T ....T....BT...T ..T......BTTTTT .T.T.T....TT... Of 225 cells, 110 are trees of which 4 are currently burning. (48.889%, 1.778%) Print/Quit/<int>/<return> 4:
REALbasic
This example puts all of the forestry logic into a Thread class. This allows the UI to remain responsive while the Thread does all the work in the background. We create a Thread by subclassing the Thread object in the IDE, in this case creating forestfire as a subclass of the Thread object and put the following code in its Run() event: <lang realbasic> Sub Run()
//Handy named constants Const empty = 0 Const tree = 1 Const fire = 2 Const ablaze = &cFF0000 //Using the &c numeric operator to indicate a color in hex Const alive = &c00FF00 Const dead = &c804040 //Our forest Dim worldPic As New Picture(480, 480, 32) Dim newWorld(120, 120) As Integer Dim oldWorld(120, 120) As Integer //Initialize forest Dim rand As New Random For x as Integer = 0 to 119 For y as Integer = 0 to 119 if rand.InRange(0, 2) = 0 Or x = 119 or y = 119 or x = 0 or y = 0 Then newWorld(x, y) = empty worldPic.Graphics.ForeColor = dead worldPic.Graphics.FillRect(x*4, y*4, 4, 4) Else newWorld(x, y) = tree worldPic.Graphics.ForeColor = alive worldPic.Graphics.FillRect(x*4, y*4, 4, 4) end if Next Next oldWorld = newWorld //Burn, baby burn! While Window1.stop = False For x as Integer = 0 To 119 For y As Integer = 0 to 119 Dim willBurn As Integer = rand.InRange(0, Window1.burnProb.Value) Dim willGrow As Integer = rand.InRange(0, Window1.growProb.Value) if x = 119 or y = 119 or x = 0 or y = 0 Then Continue end if Select Case oldWorld(x, y) Case empty If willGrow = (Window1.growProb.Value) Then newWorld(x, y) = tree worldPic.Graphics.ForeColor = alive worldPic.Graphics.FillRect(x*4, y*4, 4, 4) end if Case tree if oldWorld(x - 1, y) = fire Or oldWorld(x, y - 1) = fire Or oldWorld(x + 1, y) = fire Or oldWorld(x, y + 1) = fire Or oldWorld(x + 1, y + 1) = fire Or oldWorld(x - 1, y - 1) = fire Or oldWorld(x - 1, y + 1) = fire Or oldWorld(x + 1, y - 1) = fire Or willBurn = (Window1.burnProb.Value) Then newWorld(x, y) = fire worldPic.Graphics.ForeColor = ablaze worldPic.Graphics.FillRect(x*4, y*4, 4, 4) end if Case fire newWorld(x, y) = empty worldPic.Graphics.ForeColor = dead worldPic.Graphics.FillRect(x*4, y*4, 4, 4) End Select Next Next Window1.Canvas1.Graphics.DrawPicture(worldPic, 0, 0) oldWorld = newWorld me.Sleep(Window1.speed.Value) Wend
End Sub </lang> As you can see, this Thread is expecting a Window object called Window1 with several other objects within it. The IDE will automatically create a Window object called Window1 when a new GUI application is created. Our Window1 has 5 objects (widgets) in it: a Canvas (for displaying graphics), three sliders, and a pushbutton. <lang realbasic> Sub Open()
//First method to run on the creation of a new Window. We instantiate an instance of our forestFire thread and run it. Dim fire As New forestFire fire.Run()
End Sub
stop As Boolean //a globally accessible property of Window1. Boolean properties default to False.
Sub Pushbutton1.Action()
stop = True
REXX
This version has been elided, otherwise the size of the program (with all it's options and optional formatting) would
probably be on the big side for general viewing, and maybe a wee bit complex to demonstrate how to program for this task.
If repeatable results are desired, the RANDSEED variable can be set to a positive integer.
Glyphs were chosen in an attempt to pictorialize a tree (↑) and also a fire (▒).
The choice of glyphs within the DOS code page (under Windoes) is rather limited.
There are two dependencies: the LINESIZE function is used (some REXXes don't have it), and the RYO
version that I wrote was wasn't included here. Also, the CLS (DOS) command is used to clear the screen.
<lang rexx>/*REXX program grows and displays a forest (with growth and lightning).
┌───────────────────────────elided version─────────────────────────┐ ├─── full version has many more options and enhanced displays. ────┤ └──────────────────────────────────────────────────────────────────┘ */
signal on syntax; signal on novalue /*handle REXX program errors. */ signal on halt /*handle cell growth interruptus.*/ parse arg peeps '(' generations rows cols bare! life! clearscreen every @abc='abcdefghijklmnopqrstuvwxyz'; @abcU=@abc; upper @abcU
blank = 'BLANK'
generations = p(generations 100)
rows = p(rows 3) cols = p(cols 3) bare! = pickchar(bare! blank)
clearscreen = p(clearscreen 0)
every = p(every 999999999) life! = pickchar(life! '☼')
fents=max(79,cols) /*fence width shown after display*/ $.=bare! /*the universe is new, and barren*/ gens=abs(generations) /*use this for convenience. */ x=space(peeps) /*remove superfluous spaces. */ if x== then x='2,1 2,2 2,3'
do while x \== parse var x p x; parse var p r ',' c .; $.r=overlay(life!,$.r,c+1) end
life=0; !.=0; call showCells /*show initial state of the cells*/ /*─────────────────────────────────────watch cell colony grow/live/die. */
do life=1 for gens do r=1 for rows; rank=bare! do c=2 for cols; ?=substr($.r,c,1); ??=?; n=neighbors() select /*select da quickest choice first*/ when ?==bare! then if n==3 then ??=life! otherwise if n<2 | n>3 then ??=bare! end /*select*/ rank=rank || ?? end /*c*/ @.r=rank end /*c*/
do r=1 for rows; $.r=@.r; end /*assign alternate cells ──► real*/ if life//every==0 | generations>0 | life==gens then call showCells end /*life*/
/*─────────────────────────────────────stop watching the universe (life)*/ halt: cycles=life-1; if cycles\==gens then say 'REXX program interrupted.' exit /*stick a fork in it, we're done.*/ /*───────────────────────────────SHOWCELLS subroutine─-─────────────────*/ showCells: if clearscreen then 'CLS' /* ◄─── change this for your OS.*/ _=; do r=rows by -1 for rows /*show the forest in proper order*/
z=strip(substr($.r,2),'T') /*pick off the meat of the row. */ say z; _=_ || z /*be neat about trailing blanks. */ end /*r*/
say right(copies('═',fents)life,fents) /*show&tell for a stand of trees.*/ if _== then exit /*if no life, then stop the run. */ if !._ then do; say 'repeating ...'; exit; end !._=1 /*assign a state & compare later.*/ return /*───────────────────────────────NEIGHBORS subroutine───────────────────*/ neighbors: rp=r+1; cp=c+1; rm=r-1; cm=c-1 /*count 8 neighbors of a cell*/ return (substr($.rm,cm,1)==life!) + (substr($.rm,c ,1)==life!) + ,
(substr($.rm,cp,1)==life!) + (substr($.r ,cm,1)==life!) + , (substr($.r ,cp,1)==life!) + (substr($.rp,cm,1)==life!) + , (substr($.rp,c ,1)==life!) + (substr($.rp,cp,1)==life!)
/*───────────────────────────────1-liner subroutines────────────────────*/ err: say;say;say center(' error! ',max(40,linesize()%2),"*");say;do j=1 for arg();say arg(j);say;end;say;exit 13 novalue: syntax: call err 'REXX program' condition('C') "error",condition('D'),'REXX source statement (line' sigl"):",sourceline(sigl) pickchar: _=p(arg(1));if translate(_)==blank then _=' ';if length(_) ==3 then _=d2c(_);if length(_) ==2 then _=x2c(_);return _ p: return word(arg(1),1)</lang> output when using the defaults of:
- generations = 100
- rows = 39
- columns = 79 (one less than the window size)
- lightning rate = ½%
- new growth rate = 6%
- bare character = blank
- fire character = ▒
- tree character = ↑
This is the 7th generation (out of 100).
↑↑↑↑↑↑↑↑▒▒▒▒▒▒▒▒▒ ↑↑↑↑↑↑ ▒↑↑↑↑▒ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑▒▒▒↑↑↑ ↑↑↑↑↑↑↑↑▒ ↑↑↑↑↑↑↑ ▒↑↑↑↑▒ ↑↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑▒ ↑ ↑ ↑↑↑↑↑↑ ▒↑↑↑↑▒ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑↑↑ ▒↑↑▒▒▒▒▒▒▒▒▒▒▒▒▒▒↑↑↑ ↑↑↑↑↑↑↑↑▒ ↑↑↑↑ ↑↑ ↑↑↑↑ ▒↑↑↑↑▒ ↑↑↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑ ▒▒▒▒ ▒↑↑↑ ↑↑↑↑↑↑↑↑▒ ↑↑↑↑↑↑ ↑ ▒↑↑↑↑▒ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑↑ ↑ ▒↑↑↑ ↑↑↑↑↑↑↑↑▒ ↑↑↑↑↑↑↑↑↑ ▒▒▒▒▒▒▒↑↑↑↑▒▒▒▒▒▒▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒▒ ↑↑ ↑↑ ↑↑↑↑▒ ↑ ▒▒↑↑ ↑↑↑↑↑↑↑↑▒ ↑↑↑↑↑↑↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒▒▒▒▒▒▒▒▒▒▒▒ ↑↑↑↑↑↑↑ ↑▒ ▒↑↑↑ ▒↑↑ ↑↑↑↑↑↑↑↑▒ ↑↑↑↑↑↑↑↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑↑↑↑↑↑ ↑ ↑ ↑▒ ▒↑↑↑ ▒↑↑ ↑↑↑↑↑↑↑↑▒ ↑↑↑↑↑↑↑↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑ ↑↑↑↑↑↑ ↑↑↑↑↑↑ ↑↑▒▒▒ ↑ ↑↑ ▒↑↑ ↑↑↑↑↑↑↑↑▒ ↑↑▒▒▒↑↑↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑↑↑↑↑ ↑ ↑↑ ↑↑↑↑↑ ↑↑▒ ▒▒▒ ↑ ▒▒▒ ↑↑▒↑↑↑↑↑▒ ▒▒▒ ▒ ↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑ ▒▒▒↑▒↑▒↑ ↑↑ ↑ ↑ ▒ ↑ ↑ ↑ ↑↑↑↑↑↑↑↑▒ ▒↑↑ ▒↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑↑▒ ↑ ▒ ↑ ↑↑ ↑↑▒ ▒↑ ↑ ▒▒▒▒▒▒▒▒▒ ↑▒▒ ▒↑↑ ▒▒▒▒▒▒▒▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ▒↑ ↑ ▒↑ ↑ ↑ ↑↑↑↑ ↑↑ ↑ ▒▒▒▒↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ▒ ↑↑ ▒▒ ▒ ▒▒ ▒▒ ↑ ↑↑↑↑↑ ↑ ↑↑ ↑ ↑↑▒ ↑↑↑↑↑↑↑↑↑↑↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ▒▒ ▒↑ ▒ ↑↑ ▒▒ ▒ ▒ ▒▒↑▒▒↑↑↑ ↑↑↑ ↑↑↑↑↑↑ ↑↑ ↑↑ ↑↑ ↑ ↑ ▒↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑▒ ↑↑ ↑↑ ▒↑↑↑ ▒▒ ▒▒ ↑▒↑↑ ↑↑↑↑↑↑↑↑ ↑ ↑↑↑▒ ▒ ↑↑▒▒▒ ▒↑↑↑↑↑↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑▒ ▒▒▒▒↑↑↑ ▒▒ ↑↑ ▒↑↑↑ ↑↑↑↑↑↑↑ ↑▒▒ ↑ ↑↑ ▒ ↑▒ ▒▒▒↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑▒▒▒↑▒↑↑ ↑↑ ▒▒ ↑↑▒▒↑↑↑ ↑↑↑↑↑↑↑ ↑ ▒ ↑▒ ▒↑↑ ▒ ↑ ▒ ▒↑↑ ▒▒▒▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑↑ ↑↑↑↑↑↑↑↑↑ ▒▒▒ ↑↑ ▒↑↑↑↑↑↑↑↑↑↑ ▒ ↑ ▒↑↑↑↑ ↑↑↑ ▒ ↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑↑↑↑↑ ↑ ↑↑↑ ▒↑▒ ↑▒ ↑↑↑↑↑↑↑ ↑↑↑▒ ▒↑↑↑▒▒ ▒▒ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑↑↑ ↑↑↑ ↑↑↑ ▒↑▒ ↑↑↑↑↑↑↑↑↑ ↑↑↑▒▒▒▒↑↑ ↑▒ ↑↑ ▒↑ ↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ▒▒↑▒ ↑ ↑↑ ↑↑↑↑ ▒▒▒▒ ↑↑↑↑↑↑↑↑ ↑↑↑ ↑↑ ↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒↑↑▒ ↑↑↑↑↑↑↑↑↑↑ ▒↑↑↑ ↑↑↑↑↑↑ ↑ ↑↑↑▒▒▒ ▒↑ ▒ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑ ↑↑↑ ↑↑↑ ▒↑↑↑ ↑↑↑↑↑↑↑↑↑ ↑↑↑▒ ↑ ↑▒ ↑ ▒▒▒▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑↑ ↑ ▒↑↑↑ ↑↑↑↑↑↑ ↑ ↑↑↑▒ ▒ ↑↑ ↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒▒ ▒↑↑↑ ↑↑↑↑↑ ↑ ↑ ↑ ▒↑↑▒▒▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒▒▒▒▒▒▒▒▒▒▒▒▒▒↑↑↑ ↑↑↑↑ ↑ ↑↑↑ ▒ ▒↑↑▒ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑ ↑↑↑ ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒↑↑▒▒▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑ ↑↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ▒▒▒▒▒▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒▒▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ▒▒▒▒▒▒▒▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒↑↑↑↑↑▒▒▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒▒▒▒▒▒▒↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ▒▒↑↑↑↑↑↑↑↑↑↑↑▒▒▒▒▒▒▒↑↑↑↑↑↑▒ ▒↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑↑↑ ↑↑↑↑ ↑↑ ↑ ▒↑↑↑↑↑↑↑↑↑↑↑▒ ▒▒▒▒▒▒▒▒ ↑ ▒↑↑↑↑↑↑↑↑↑↑ ▒▒▒▒▒▒▒▒↑↑↑↑↑↑↑▒ ↑↑↑↑↑ ↑ ↑↑ ↑↑↑▒ ▒↑↑↑↑↑↑↑↑↑↑↑▒ ↑ ↑↑ ▒↑↑↑↑↑↑↑↑↑↑ ▒↑↑↑↑↑↑↑▒ ↑↑↑ ↑↑↑↑ ↑↑▒↑ ▒↑↑↑↑↑↑↑↑↑↑↑▒ ↑↑↑ ↑ ↑ ↑↑ ▒↑▒▒▒▒▒▒▒↑↑ ↑↑ ↑ ▒↑↑↑↑↑↑↑▒ ↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑ ▒↑↑↑↑↑↑↑↑↑↑↑▒ ↑ ↑ ↑↑↑ ↑ ↑↑↑ ▒↑▒ ▒↑↑ ↑ ↑↑ ▒↑↑↑↑↑↑↑▒ ↑↑ ↑ ↑ ↑ ↑↑↑↑↑↑ ▒↑↑↑↑↑↑↑↑↑↑↑▒ ↑ ↑↑↑↑↑↑↑ ▒▒▒↑▒↑ ↑ ▒↑↑ ↑ ↑ ▒▒▒▒↑↑↑↑▒ ↑↑↑ ↑↑ ↑↑↑ ↑↑ ▒↑↑↑↑↑↑↑↑↑↑↑▒▒▒▒ ↑↑ ↑↑↑↑↑ ▒↑↑↑▒ ↑↑↑ ▒↑↑ ↑↑↑↑ ▒↑↑↑↑▒ ↑↑↑ ↑ ▒▒▒ ↑ ↑↑↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑ ↑↑↑↑↑↑ ▒↑↑↑▒ ↑ ▒↑↑ ↑↑↑ ▒↑↑↑↑▒ ▒↑▒ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒▒▒ ↑↑↑↑↑↑↑ ▒↑↑↑▒ ▒↑↑ ▒↑↑↑↑▒▒▒▒▒▒▒▒▒▒▒↑▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒↑↑↑↑↑↑↑↑↑▒ ↑ ↑↑↑↑ ↑ ▒↑↑↑▒▒▒▒▒▒▒↑↑ ▒▒▒▒▒▒▒▒▒▒▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ▒↑▒▒▒↑↑↑↑↑▒ ↑ ↑↑↑↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑ ▒↑▒ ▒↑↑↑↑↑▒ ↑↑ ↑ ↑ ▒↑↑↑ ↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒ ↑ ▒↑▒▒▒↑↑↑↑↑▒ ▒↑↑↑↑↑↑↑↑↑↑↑↑ ═════════════════════════════════════════════════════════════════════════════10
Ruby
<lang ruby>require 'enumerator'
def transition arr, tree_prob, fire_prob
arr.enum_with_index.map do |cell, i| if i == 0 or i == arr.length - 1 # boundary conditions: cells are always empty here :empty else case cell when :fire # burning cells become empty :empty when :empty # empty cells grow a tree with probability tree_prob rand < tree_prob ? :tree : :empty when :tree # check my neighbouring cells, are they on fire? if arr[i - 1] == :fire or arr[i + 1] == :fire :fire else # neighbours not on fire, but catch fire at random rand < fire_prob ? :fire : :tree end end end end
end
def pretty_print arr
# colour the trees green, the fires red, and the empty spaces black print(arr.map { |cell| "\e[3" + case cell when :tree "2mT" when :fire "1mF" when :empty "0m " end + "\e[0m" }.join)
end
N = 20 # 20 trees P = 0.5 # probability of growing a tree F = 0.1 # probability of catching on fire
srand Time.now.to_i
- each cell has a 50/50 chance of being a tree
array = (1..N).map { rand < 0.5 ? :tree : :empty } array[0] = array[-1] = :empty # boundary conditions pretty_print array puts
begin
array = transition(array, P, F)
pretty_print array
Run BASIC
<lang runbasic>graphic #g, 200,200 dim preGen(200,200) dim newGen(200,200)
for gen = 1 to 200
for x = 1 to 199 for y = 1 to 199 select case preGen(x,y) case 0 if rnd(0) > .99 then newGen(x,y) = 1 : #g "color green ; set "; x; " "; y case 2 newGen(x,y) = 0 : #g "color brown ; set "; x; " "; y case 1 if preGen(x-1,y-1) = 2 or preGen(x-1,y) = 2 or preGen(x-1,y+1) = 2 _ or preGen(x,y-1) = 2 or preGen(x,y+1) = 2 or preGen(x+1,y-1) = 2 _ or preGen(x+1,y) = 2 or preGen(x+1,y+1) = 2 or rnd(0) > .999 then #g "color red ; set "; x; " "; y newGen(x,y) = 2 end if end select preGen(x-1,y-1) = newGen(x-1,y-1) next y next x
Sather
<lang sather>class FORESTFIRE is
private attr fields:ARRAY{ARRAY{INT}}; private attr swapu:INT; private attr rnd:RND; private attr verbose:BOOL; private attr generation:INT; readonly attr width, height:INT; const empty:INT := 0; const tree:INT := 1; const burning:INT := 2;
attr prob_tree, prob_p, prob_f :FLT;
create(w, h:INT, v:BOOL):SAME is res:FORESTFIRE := new; res.fields := #(2); res.fields[0] := #(w*h); res.fields[1] := #(w*h); res.width := w; res.height := h; res.swapu := 0; res.prob_tree := 0.55; res.prob_p := 0.001; res.prob_f := 0.00001; res.rnd := #RND; res.verbose := v; res.generation := 0; res.initfield; return res; end;
-- to give variability seed(i:INT) is rnd.seed(i); end;
create(w, h:INT):SAME is res ::= create(w, h, false); return res; end;
initfield is n ::= 0; swapu := 0; if verbose and generation > 0 then #ERR + "Previous generation " + generation + "\n"; end; generation := 0; loop i ::= 0.upto!(width-1); loop j ::= 0.upto!(height-1); if rnd.uniform > prob_tree.fltd then cset(i, j, empty); else
n := n + 1;
cset(i, j, tree); end; end; end; if verbose then #ERR + #FMT("Field size is %dx%d (%d)", width, height, size) + "\n"; #ERR + "There are " + n + " trees (" + (100.0*n.flt/size.flt) + "%)\n"; #ERR + "prob_tree = " + prob_tree + "\n"; #ERR + "prob_f = " + prob_f + "\n"; #ERR + "prob_p = " + prob_p + "\n"; #ERR + "ratio = " + prob_p/prob_f + "\n"; end; end;
field:ARRAY{INT} is return fields[swapu]; end;
ofield:ARRAY{INT} is return fields[swapu.bxor(1)]; end; size:INT is return width*height; end;
set(i, j, t:INT) pre bcheck(i, j) is ofield[j*width + i] := t; end;
cset(i, j, t:INT) pre bcheck(i, j) is field[j*width + i] := t; end;
private bcheck(i, j:INT):BOOL is if i.is_between(0, width-1) and j.is_between(0, height-1) then return true; -- is inside else return false; -- is outside end; end;
get(i, j:INT):INT is if ~bcheck(i, j) then return empty; end; return field[j*width + i]; end;
oget(i, j:INT):INT is if ~bcheck(i, j) then return empty; end; return ofield[j*width + i]; end;
burning_neighbor(i, j:INT):BOOL is loop x ::= (-1).upto!(1); loop y ::= (-1).upto!(1); if x /= y then if get(i+x, j+y) = burning then return true; end; end; end; end; return false; end;
evolve is bp ::= 0; loop i ::= 0.upto!(width-1); loop j ::= 0.upto!(height-1);
case get(i, j)
when burning then set(i, j, empty); bp := bp + 1; when empty then if rnd.uniform > prob_p.fltd then set(i, j, empty); else set(i, j, tree); end; when tree then if burning_neighbor(i, j) then set(i, j, burning); else if rnd.uniform > prob_f.fltd then set(i, j, tree); else set(i, j, burning); end; end; else #ERR + "corrupted field\n"; end; end; end; generation := generation + 1; if verbose then if bp > 0 then #ERR + #FMT("Burning at gen %d: %d\n", generation-1, bp); end; end; swapu := swapu.bxor(1); end;
str:STR is s ::= ""; loop j ::= 0.upto!(height -1); loop i ::= 0.upto!(width -1); case get(i, j) when empty then s := s + "."; when tree then s := s + "Y"; when burning then s := s + "*"; end; end; s := s + "\n"; end; s := s + "\n"; return s; end;
end;
class MAIN is
main is forestfire ::= #FORESTFIRE(74, 40); -- #FORESTFIRE(74, 40, true) to have some extra info -- (redirecting stderr to a file is a good idea!)
#OUT + forestfire.str; -- evolve 1000 times loop i ::= 1000.times!; forestfire.evolve; -- ANSI clear screen sequence #OUT + 0x1b.char + "[H" + 0x1b.char + "[2J"; #OUT + forestfire.str; end; end;
end;</lang>
Scala
<lang scala>import scala.util.Random
class Forest(matrix:Array[Array[Char]]){
import Forest._ val f=0.01; // auto combustion probability val p=0.1; // tree creation probability val rows=matrix.size val cols=matrix(0).size
def evolve():Forest=new Forest(Array.tabulate(rows, cols){(y,x)=> matrix(y)(x) match { case EMPTY => if (Random.nextDouble<p) TREE else EMPTY case BURNING => EMPTY case TREE => if (neighbours(x, y).exists(_==BURNING)) BURNING else if (Random.nextDouble<f) BURNING else TREE } }) def neighbours(x:Int, y:Int)=matrix slice(y-1, y+2) map(_.slice(x-1, x+2)) flatten override def toString()=matrix map (_.mkString("")) mkString "\n"
}
object Forest{
val TREE='T' val BURNING='#' val EMPTY='.' def apply(x:Int=30, y:Int=15)=new Forest(Array.tabulate(y, x)((y,x)=> if (Random.nextDouble<0.5) TREE else EMPTY))
}</lang>
<lang scala>object ForestFire{
def main(args: Array[String]): Unit = { var l=Forest() for(i <- 0 until 20){ println(l+"\n-----------------------") l=l.evolve } }
}</lang> Sample output:
.T..TTT.TT .T..TTT.TT TT..TTT.TT TT..TTTTTT TT..TTTTTT TTT.TTTT.. TTT.TTTTT. TTT.TTTTT. TTT.TTTTT. TTT.TTTTT. .T...T..T. .TT..T..T. .TT..T.TT. .TT.TT.TTT .TT.##.TTT T...TT.T.T T...TT.T.T T...TT.T.T T.TT##.T.T T.T#...T.T .T..TTTTTT .T..TTTTTT .T..#TTTTT .T...#TTTT .T....#TTT TTT..TTTT. TTT..TTTT. TTT..TTTT. TTT..#TTT. ###...##T. TT.TTTTTTT TT.TTTTTTT TT.TTTTTTT ##.TTT#TTT ...###.#TT ......TT.. T.....TT.. #.T.TTTT.. .T#.TTTT.. .#..####.. .TTT.TTTTT .#TT.TTTTT ..#T.TTTTT ...#.TTTTT .....TTTTT T.T.TTT.T. TTT.TTT.T. ###.TTT.T. ...TTTT.T. T..##TT.T.
Tcl
<lang tcl>package require Tcl 8.5
- Build a grid
proc makeGrid {w h {treeProbability 0.5}} {
global grid gridW gridH set gridW $w set gridH $h set grid [lrepeat $h [lrepeat $w " "]] for {set x 0} {$x < $w} {incr x} {
for {set y 0} {$y < $h} {incr y} { if {rand() < $treeProbability} { lset grid $y $x "#" } }
}
}
- Evolve the grid (builds a copy, then overwrites)
proc evolveGrid {{fireProbability 0.01} {plantProbability 0.05}} {
global grid gridW gridH set newGrid {} for {set y 0} {$y < $gridH} {incr y} {
set row {} for {set x 0} {$x < $gridW} {incr x} { switch -exact -- [set s [lindex $grid $y $x]] { " " { if {rand() < $plantProbability} { set s "#" } } "#" { if {[burningNeighbour? $x $y] || rand() < $fireProbability} { set s "o" } } "o" { set s " " } } lappend row $s } lappend newGrid $row
} set grid $newGrid
}
- We supply the neighbourhood model as an optional parameter (not used...)
proc burningNeighbour? {
x y {neighbourhoodModel {-1 -1 -1 0 -1 1 0 -1 0 1 1 -1 1 0 1 1}}
} {
global grid gridW gridH foreach {dx dy} $neighbourhoodModel {
set i [expr {$x + $dx}] if {$i < 0 || $i >= $gridW} continue set j [expr {$y + $dy}] if {$j < 0 || $j >= $gridH} continue if {[lindex $grid $j $i] eq "o"} { return 1 }
} return 0
}
proc printGrid {} {
global grid foreach row $grid {
puts [join $row ""]
}
}
- Simple main loop; press Return for the next step or send an EOF to stop
makeGrid 70 8 while 1 {
evolveGrid printGrid if {[gets stdin line] < 0} break
}</lang> Sample output:
### # ####### ## # ## ##### # # # ### ## # # # ## # ##### # ## # # ## o ### # # #### # # #### # # ####### ### ##### ### #### ####### ### ## ## #### # ## # ### ## #### # ## # # #### # ### # # ## ##### # # ## # ##### ### # ## # ## ###### # #### ## # # ### ### # ##### # ### ## # ### # ####### #### # # # # # # # # # # # #### ### # ## ## ### # ## # # # # # ## # ## ## ##### ## ## # # # # ## # ## ### # # # ### ## ## # ### # # ### # ### ##### # # ####### ## # #o o#### # # # ### ## # # # # #o # ##### # ## ## # ## ### # # #### # # #### # # ####### ### ##### ### #### #####oo ### ### ## #### # ## # ### ## #### # ## # # #### # ### # # ## ##### # # ## # ##### ### # ## # ## ###### # #o## ## # # ### ### # ###### # ### ## # ### # ####### #### # # # # # # # # # # # #### ### # ## ## ### # ## # # # # # ## # ## ## o#### ## ## # # # # ## # ## ### # # # ### ## # ## # ### # # ### # #oo o#### # # ######## ## # o o### ## # # #o# ## # # # # o # ##### # ## ## # ## o## # # #### # # ##o# # # ######o ### ##### #### #### ####o ### # ### ## #### ## ## ##### ## #### # ## # # o o### # ### o # ## ##### # # ## ## ##### ### # ## # ## ###### # o o# ## # # ### ##### ###### # ### ## # ### # ####### #### o o # # # o # o # # # # #### ##### ## ### ### # ## # # # # # ## # ## ## o### ## ## # # # # ## # ## ### # ### ### ## # ## # #o# # # ### # o o### # # ######## ## # o## ## # # o o oo## # # # # # # ##### # ## ## # ## o# # # #### o o #o o # # #####o ### ##### #### #### ###o o## ####o o# #### #o o# ##### #o o### # ### # # o## # ##o # ## ###### # # ## ## ##### ### # ## # ## oooo## # o oo # # ### ##### ###### ##### ## # ### # ####### #### # # o # # # # # #### ##### ## ### ### # ## # # # # o### # oo ## o## ## ## # # # # ## # o# ### # ### ###### # ## # o o # # #### # o## # # ######## ## # o# ## # # # o# # # # o # o ##### # ## ## # #o o # o ooo# o # # # ####o ### ##### o### #### ##o # o# ##oo o oooo#o o# ###### o o## # # ### # # oo # #o o ## ooooo# # # oo o# # ##### ### # ## # ## o# #o # # # ### ##### ###### ##### ## # ### # oooooo# #### o # # o o # # # #### ##### ## ### o## # ## # # # # o## o# #o# o# ## ## # # # # ## ## o ### # ### # #####o # ## # #
Visual Basic .NET
This program sits behind a Windows form with fixed borders, the only component of which is a timer (named Timer1, set to something like 50 or 100ms depending on the speed the user wants to see it). Other constant values (the probabilities and the window dimensions) can be set at the top of the code.
<lang VisualBasic.NET>Public Class ForestFire
Private _forest(,) As ForestState Private _isBuilding As Boolean Private _bm As Bitmap Private _gen As Integer Private _sw As Stopwatch
Private Const _treeStart As Double = 0.5 Private Const _f As Double = 0.00001 Private Const _p As Double = 0.001
Private Const _winWidth As Integer = 300 Private Const _winHeight As Integer = 300
Private Enum ForestState Empty Burning Tree End Enum
Private Sub ForestFire_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Me.ClientSize = New Size(_winWidth, _winHeight) ReDim _forest(_winWidth, _winHeight)
Dim rnd As New Random() For i As Integer = 0 To _winHeight - 1 For j As Integer = 0 To _winWidth - 1 _forest(j, i) = IIf(rnd.NextDouble <= _treeStart, ForestState.Tree, ForestState.Empty) Next Next
_sw = New Stopwatch _sw.Start() DrawForest() Timer1.Start() End Sub
Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick If _isBuilding Then Exit Sub
_isBuilding = True GetNextGeneration()
DrawForest() _isBuilding = False End Sub
Private Sub GetNextGeneration() Dim forestCache(_winWidth, _winHeight) As ForestState Dim rnd As New Random()
For i As Integer = 0 To _winHeight - 1 For j As Integer = 0 To _winWidth - 1 Select Case _forest(j, i) Case ForestState.Tree If forestCache(j, i) <> ForestState.Burning Then forestCache(j, i) = IIf(rnd.NextDouble <= _f, ForestState.Burning, ForestState.Tree) End If
Case ForestState.Burning For i2 As Integer = i - 1 To i + 1 If i2 = -1 OrElse i2 >= _winHeight Then Continue For For j2 As Integer = j - 1 To j + 1 If j2 = -1 OrElse i2 >= _winWidth Then Continue For If _forest(j2, i2) = ForestState.Tree Then forestCache(j2, i2) = ForestState.Burning Next Next forestCache(j, i) = ForestState.Empty
Case Else forestCache(j, i) = IIf(rnd.NextDouble <= _p, ForestState.Tree, ForestState.Empty) End Select Next Next
_forest = forestCache _gen += 1 End Sub
Private Sub DrawForest() Dim bmCache As New Bitmap(_winWidth, _winHeight)
For i As Integer = 0 To _winHeight - 1 For j As Integer = 0 To _winWidth - 1 Select Case _forest(j, i) Case ForestState.Tree bmCache.SetPixel(j, i, Color.Green)
Case ForestState.Burning bmCache.SetPixel(j, i, Color.Red) End Select Next Next
_bm = bmCache Me.Refresh() End Sub
Private Sub ForestFire_Paint(ByVal sender As System.Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles MyBase.Paint e.Graphics.DrawImage(_bm, 0, 0)
Me.Text = "Gen " & _gen.ToString() & " @ " & (_gen / (_sw.ElapsedMilliseconds / 1000)).ToString("F02") & " FPS: Forest Fire" End Sub
End Class</lang>