programs/stencil.c

#include <stdio.h>
#include <stdlib.h>
#define N 5000
int main() {
    double **g=malloc(N*sizeof(double*)),**n=malloc(N*sizeof(double*));
    for(int i=0;i<N;i++){g[i]=malloc(N*sizeof(double));n[i]=malloc(N*sizeof(double));
    for(int j=0;j<N;j++)g[i][j]=(double)(i+j);}
    for(int t=0;t<10;t++)for(int i=1;i<N-1;i++)for(int j=1;j<N-1;j++)
    n[i][j]=0.25*(g[i-1][j]+g[i+1][j]+g[i][j-1]+g[i][j+1]);
    printf("%f\n",n[N/2][N/2]);return 0;
}