Forest fire
From Rosetta Code
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) |
Implement the Drossel and Schwabl definition of the forest-fire model.
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.
[edit] 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;
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
[edit] ALGOL 68
[edit] Textual version
Note: This specimen retains the original D coding style.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
)
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 -----------------------------------------------------------------
[edit] 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.
; 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
}
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
[edit] BBC BASIC
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
Output:
[edit] 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);
}
[edit] Console version
C99. Uncomment srand() for variaty, usleep() for slower speed.
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
enum { empty = 0, tree = 1, fire = 2 };
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);
}
[edit] C#
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;
}
}
}
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
[edit] 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)
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))
[edit] Common 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)))))
Example results:
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
[edit] D
[edit] Textual Version
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);
}
}
- 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
[edit] Graphical Version
(With Image class made final).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);
});
}
About 34 FPS, 600x600 cells.
[edit] F#
This implementation can be compiled or run in the interactive F# shell.
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
[edit] 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
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
[edit] 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.
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'
}
}
}
}
}
[edit] 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
A run:
*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
[edit] Icon and Unicon
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
printf.icn provides printf graphics.icn provides graphics
[edit] 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.
)
Example use:
run 2
##### #
# #
### ####
# # # #
##### #
## # #
# #
o## #
##### #
# #
### ####
# # # #
##### #
## # #
o #
o# #
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).
[edit] Java
[edit] Text
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);
}
}
[edit] Graphics
See: Forest fire/Java/Graphics
[edit] JAMES II/Rule-based Cellular Automata
@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;
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.
[edit] 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);
To actually see it work we need a small demo page with HTML5 compliant code:
<!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>
The output is a (mostly fluent) animation of the area.
[edit] Liberty BASIC
'[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
[edit] 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.
evolve[nbhd_List, k_] := 0 /; nbhd[[2, 2]] == 2 (*burning->empty*)
evolve[nbhd_List, k_] := 2 /; nbhd[[2, 2]] == 1 && Max@nbhd == 2 (*near_burning&nonempty->burning*)
evolve[nbhd_List, k_] := RandomChoice[{f, 1 - f} -> {2, nbhd[[2, 2]]}] /; nbhd[[2, 2]] == 1 && Max@nbhd < 2 (*spontaneously combusting tree*)
evolve[nbhd_List, k_] := RandomChoice[{p, 1 - p} -> {1, nbhd[[2, 2]]}] /; nbhd[[2, 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]
[edit] OCaml
This example uses a curses display (with the ocaml-curses bindings).
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()
You can execute this script with:
$ ocaml unix.cma -I +curses curses.cma forest.ml
[edit] Perl
Requires terminal that understands ANSI escape sequences:
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);
[edit] Perl 6
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;
}
[edit] 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) ) ) ) ) ) )
Use:
(forestFire 26 0.5 0.01 0.001)
[edit] 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
[edit] 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
EndIf
[edit] 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.
'''
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
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:
[edit] 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:
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
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.
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
End Sub
[edit] 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.
/*REXX program grow and display a forest (with groweth and lightning). */
/*──────────────────────────────────────────────────────────────────────*/
/*───────────────────────────── elided version ───────────────────────*/
/*───── full version has many more options and enhanced displayes.──────*/
/*──────────────────────────────────────────────────────────────────────*/
signal on syntax; signal on novalue /*handle REXX program errors. */
signal on halt /*handle growth interruptus. */
_= /*(below) nullify some options. */
parse var _ generations rows cols birth lightning bare@ fire@ tree@,
randseed listopts clearscreen every
@abc='abcdefghijklmnopqrstuvwxyz'; @abcU=@abc; upper @abcU
percent=100 /*handy-dandy constant for using%*/
field=percent**2 /*size of the probability field. */
if randseed\=='' then call random ,,randseed
blank='BLANK'
generations=p(generations 100)
rows=p(rows 40-1)
cols=p(cols max(80,linesize())-1)
bare@=pickchar(bare@ blank)
fire@=pickchar(fire@ '▒')
tree@=pickchar(tree@ '18'x)
listopts=p(listopts 0)
clearscreen=p(clearscreen 1)
every=p(every 999999999)
birth=p(strip(birth,,'%') 6)*percent
lightning=p(strip(lightning,,'%') 1/2)*percent
new.=bare@ /*the forest is a field, and bare*/
alt.=bare@ /*and also the alternate universe*/
gens=abs(generations) /*use this for convenience. */
/*─────────────────────────────────────watch the forest grow and/or burn*/
do life=1 for gens
do c=1 for cols
do r=1 for rows
?=alt.r.c
select /*select da quickest choice first*/
when ?==fire@ then new.r.c=bare@
when ?==bare@ then if rand()<=birth then new.r.c=tree@
otherwise if ignite?() then new.r.c=fire@
end /*select*/
alt.r.c=new.r.c
end /*r*/
end /*c*/
if life//every==0 | generations>0 |,
life==abs(generations) then call showForest
end /*life*/
/*─────────────────────────────────────stop watching the forest grow. */
halt: cycles=life-1; if cycles\==gens then say 'REXX program interrupted.'
exit
/*───────────────────────────────SHOWFOREST subroutine──────────────────*/
showForest: if clearscreen then 'CLS' /* <─── change this for your OS.*/
do r=rows by -1 for rows; _= /*show the forest in proper order*/
do c=1 for cols
_=_||new.r.c
end
say strip(_,'T') /*be neat about trailing blanks. */
end
say right(copies('=',cols)life,cols) /*show&tell for a stand of trees.*/
return
/*───────────────────────────────IGNITE? subroutine─────────────────────*/
ignite?: /*either a neighbor on fire | lightning*/
rm=r-1; if alt.c.rm ==2 then return 1
rp=r+1; if alt.c.rp ==2 then return 1
cm=c-1; if alt.cm.rm==2 then return 1
if alt.cm.r ==2 then return 1
if alt.cm.rp==2 then return 1
cp=c+1; if alt.cp.rm==2 then return 1
if alt.cp.r ==2 then return 1
if alt.cp.rp==2 then return 1
if rand()<=lightning then return 1
return 0
/*───────────────────────────────1─liner handbag/boilerplate 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)
rand: return random(1,field)
Output when using the defaults of:
generations = 100
rows = 30
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 100th screen.
↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑ ↑↑↑ ↑↑ ↑↑↑↑ ↑ ↑↑↑ ↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑ ↑▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑ ↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑ ↑ ↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑▒↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑ ↑↑ ↑↑↑↑↑ ↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑ ↑↑↑ ↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑▒↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑ ▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑ ↑↑ ↑↑↑ ↑↑↑ ↑↑ ↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑ ↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑ ↑↑↑↑↑↑↑↑↑↑ ↑ ↑↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑ ↑↑↑↑↑↑↑▒↑↑↑↑↑↑↑ ↑↑↑ ↑↑↑↑↑↑↑ ↑↑↑ ↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑ ↑↑ ↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑ ↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑ ↑↑↑ ↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑ ↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑ ↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑ ↑↑ ↑↑↑↑↑ ↑↑↑ ↑↑↑ ↑↑↑↑↑↑↑↑↑↑ ↑↑↑▒↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑ ↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑ ↑↑↑↑↑↑↑↑↑↑↑ ↑↑ ↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑ ↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑ ↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑ ↑↑▒↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑ ↑↑↑ ↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑ ↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑▒↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑ ↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑ ↑ ↑↑ ↑↑↑↑↑↑↑ ↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑ ↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑ ↑ ↑ ▒↑↑ ↑↑↑ ↑ ↑↑↑↑ ↑↑↑↑ ↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑▒↑↑↑↑↑↑↑↑↑↑↑ ↑↑↑↑ ↑↑ ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ ============================================================================100
[edit] Ruby
require 'enumerator'Sample Output:
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
end while gets.chomp.downcase != "q"
[edit] Run BASIC
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
next gen
render #g
[edit] 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;
[edit] 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))
}
object ForestFire{
def main(args: Array[String]): Unit = {
var l=Forest()
for(i <- 0 until 20){
println(l+"\n-----------------------")
l=l.evolve
}
}
}
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.
[edit] 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
}
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 # ## # #
[edit] 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.
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
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