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poisson.c
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Thu, Jul 18, 03:38

poisson.c
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#include "io_ascii.h"
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#define N 256
int main() {
int i, j;
char k;
float ** u;
float ** uo;
float ** f;
float h;
h = 1. / (N + 1);
// Allocation of arrays of pointers (columns)
u = (float **)malloc((N + 1) * sizeof(float *));
uo = (float **)malloc((N + 1) * sizeof(float *));
f = (float **)malloc((N + 1) * sizeof(float *));
// allocation of the rows
for (i = 0; i < N + 1; i++) {
u[i] = (float *)malloc((N) * sizeof(float));
uo[i] = (float *)malloc((N) * sizeof(float));
f[i] = (float *)malloc((N) * sizeof(float));
}
// initialization of u0 and f
for (i = 0; i < N + 1; i++) {
for (j = 0; j < N + 1; j++) {
u[i][j] = 0;
uo[i][j] = 0;
f[i][j] = -2. * 100. * M_PI * M_PI * sin(10. * M_PI * i * h) *
sin(10. * M_PI * j * h);
}
}
for (k = 0; k < 200; ++k) {
for (i = 0; i < N; i++) {
for (j = 0; j < N; j++) {
// computation of the new step
u[i][j] = 0.25 * (uo[i - 1][j] + uo[i + 1][j] + uo[i][j - 1] +
uo[i][j + 1] - f[i][j] * h * h);
}
}
// copy new grid in old grid
for (i = 0; i < N + 1; i++) {
for (j = 0; j < N + 1; j++) {
uo[i][j] = u[i][j];
}
}
write_to_file(N + 1, u, k, -1., 1.);
}
// de-allocation of the rows
for (i = 0; i < N + 1; i++) {
free(u[i]);
free(uo[i]);
free(f[i]);
}
return 0;
}

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