vsevolodbolshoegnezdo

#include <math.h>
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#define Max(a,b) ((a)>(b)?(a):(b))
#define N 10
double maxeps = 0.1e-7;
int itmax = 100;
int i,j,k;
double eps;
double A[N][N], B[N][N];
const double pi = acos(-1.0);
void relax(double w)
{
    for(i = 1; i <= N - 2; i++) {
        for(j = 1; j <= N - 2; j++) {
            B[i][j] = (A[i + 1][j] + A[i - 1][j] + A[i][j + 1] + A[i][j - 1]) / 4;
        }
    }
    for(i = 1; i <= N - 2; i++) {
        for(j = 1; j <= N - 2; j++) {
            eps = Max(eps, fabs(A[i][j] - w * B[i][j] - (1 - w) * A[i][j]));
            A[i][j] = w * B[i][j] + (1 - w) * A[i][j];
        }
    }
    /*for (i = 0; i < N; i++) {
        for (j = 0; j < N; j++) {
            printf("%.5lf ", A[i][j]);
        }
        printf("\n");
    }*/

}
void init();
//void wtime(double *t);
int main(int an, char **as)
{   int it, i, j;
    double time0, time1, r = 1 - (pi / (2 * N)) * (pi / (2 * N)), w;
    init();
    //wtime(&time0);
    w = 0.8;//1 / (1 - r * r / 2);
    for(it = 1; it <= itmax; it++) {
        eps = 0.;
        relax(w);
        printf( "it=%4i eps=%f\n", it,eps);
        //w = 1 / (1 - r * r * w / 4);
        if (eps < maxeps) break;
    }
    for (i = 0; i < N; i++) {
        for (j = 0; j < N; j++) {
            printf("%.5lf ", A[i][j]);
        }
        printf("\n");
    }
    printf("%.5lf\n", eps);
    //wtime(&time1);
    //printf("Time in seconds=%gs\t",time1 - time0);
    return 0;
}
void init()
{
    for(i = 0; i <= N-1; i++) {
        for(j = 0; j <= N-1; j++) {
            if(i == N - 1) {
                A[i][j]= sin(pi * (j / double(N - 1)));
            } else {
                if (i == 0) {
                    A[i][j]= sin(pi * (j / double(N - 1))) * exp(-j / double(N - 1));
                } else {
                    A[i][j] = 0;
                }
            }
            B[i][j] = A[i][j];
        }
    }
}

/*void wtime(double *t)
{
    static int sec = -1;
    struct timeval tv;
    gettimeofday(&tv, (void *)0);
    if (sec < 0) sec = tv.tv_sec;
    *t = (tv.tv_sec - sec) + 1.0e-6 * tv.tv_usec;
} */