Abelian sandpile model: Difference between revisions
Added C implementation
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0 0 0 0 0 0 2 1 2 0
0 0 0 0 0 0 0 1 0 0
</pre>
=={{header|C}}==
Writes out the initial and final sand piles to the console and the final sand pile to a PPM file.
<lang C>
#include<stdlib.h>
#include<string.h>
#include<stdio.h>
int main(int argc, char** argv)
{
int i,j,sandPileEdge, centerPileHeight, processAgain = 1,top,down,left,right;
int** sandPile;
char* fileName;
static unsigned char colour[3];
if(argc!=3){
printf("Usage: %s <Sand pile side> <Center pile height>",argv[0]);
return 0;
}
sandPileEdge = atoi(argv[1]);
centerPileHeight = atoi(argv[2]);
if(sandPileEdge<=0 || centerPileHeight<=0){
printf("Sand pile and center pile dimensions must be positive integers.");
return 0;
}
sandPile = (int**)malloc(sandPileEdge * sizeof(int*));
for(i=0;i<sandPileEdge;i++){
sandPile[i] = (int*)calloc(sandPileEdge,sizeof(int));
}
sandPile[sandPileEdge/2][sandPileEdge/2] = centerPileHeight;
printf("Initial sand pile :\n\n");
for(i=0;i<sandPileEdge;i++){
for(j=0;j<sandPileEdge;j++){
printf("%3d",sandPile[i][j]);
}
printf("\n");
}
while(processAgain == 1){
processAgain = 0;
top = 0;
down = 0;
left = 0;
right = 0;
for(i=0;i<sandPileEdge;i++){
for(j=0;j<sandPileEdge;j++){
if(sandPile[i][j]>=4){
if(i-1>=0){
top = 1;
sandPile[i-1][j]+=1;
if(sandPile[i-1][j]>=4)
processAgain = 1;
}
if(i+1<sandPileEdge){
down = 1;
sandPile[i+1][j]+=1;
if(sandPile[i+1][j]>=4)
processAgain = 1;
}
if(j-1>=0){
left = 1;
sandPile[i][j-1]+=1;
if(sandPile[i][j-1]>=4)
processAgain = 1;
}
if(j+1<sandPileEdge){
right = 1;
sandPile[i][j+1]+=1;
if(sandPile[i][j+1]>=4)
processAgain = 1;
}
sandPile[i][j] -= (top + down + left + right);
if(sandPile[i][j]>=4)
processAgain = 1;
}
}
}
}
printf("Final sand pile : \n\n");
for(i=0;i<sandPileEdge;i++){
for(j=0;j<sandPileEdge;j++){
printf("%3d",sandPile[i][j]);
}
printf("\n");
}
fileName = (char*)malloc((strlen(argv[1]) + strlen(argv[2]) + 23)*sizeof(char));
strcpy(fileName,"Final_Sand_Pile_");
strcat(fileName,argv[1]);
strcat(fileName,"_");
strcat(fileName,argv[2]);
strcat(fileName,".ppm");
FILE *fp = fopen(fileName,"wb");
fprintf(fp,"P6\n%d %d\n255\n",sandPileEdge,sandPileEdge);
for(i=0;i<sandPileEdge;i++){
for(j=0;j<sandPileEdge;j++){
colour[0] = (sandPile[i][j] + i)%256;
colour[1] = (sandPile[i][j] + j)%256;
colour[2] = (sandPile[i][j] + i*j)%256;
fwrite(colour,1,3,fp);
}
}
fclose(fp);
printf("\nImage file written to %s\n",fileName);
return 0;
}
</lang>
Console output :
<pre>
abhishek_ghosh@Azure:~/doodles$ ./a.out 10 64
Initial sand pile :
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 64 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
Final sand pile :
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 1 2 1 0 0 0
0 0 0 2 2 2 2 2 0 0
0 0 1 2 2 2 2 2 1 0
0 0 2 2 2 0 2 2 2 0
0 0 1 2 2 2 2 2 1 0
0 0 0 2 2 2 2 2 0 0
0 0 0 0 1 2 1 0 0 0
0 0 0 0 0 0 0 0 0 0
Image file written to Final_Sand_Pile_10_64.ppm
</pre>
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