48 lines
1.3 KiB
C
48 lines
1.3 KiB
C
/*
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* OpenMP version.
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*/
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#include <stdio.h>
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#include <math.h>
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#include <omp.h>
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#include "../config.h"
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#include "../utils.h"
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double *compute_jacobi(int n, double init_value, double threshold, borders b, int *iterations) {
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double *x;
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double max_diff, new_x;
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int i, j;
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int nb = n + 2; // n plus the border
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/* Initialize boundary regions */
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x = create_sa_matrix(n + 2, n + 2);
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for (i = 1; i <= n; i++) {
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x[IDX(nb, 0, i)] = b.north;
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x[IDX(nb, n + 1, i)] = b.south;
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x[IDX(nb, i, 0)] = b.west;
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x[IDX(nb, i, n + 1)] = b.east;
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}
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/* Initialize the rest of the matrix */
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for (i = 1; i <= n; i++) {
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for (j = 1; j <= n; j++) {
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x[IDX(nb, i, j)] = init_value;
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}
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}
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/* Iterative refinement of x until values converge */
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omp_set_num_threads(4);
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*iterations = 0;
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do {
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max_diff = 0;
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#pragma omp parallel for schedule(static, 20) reduction (max:max_diff) private(new_x, j) firstprivate(n, nb) shared(x)
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for (i = 1; i <= n; i++) {
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for (j = 1; j <= n; j++) {
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new_x = 0.25 * (x[IDX(nb, i - 1, j)] + x[IDX(nb, i, j + 1)] + x[IDX(nb, i + 1, j)] + x[IDX(nb, i, j - 1)]);
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max_diff = (double) fmax(max_diff, fabs(new_x - x[IDX(nb, i, j)]));
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x[IDX(nb, i, j)] = new_x;
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}
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}
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(*iterations)++;
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} while (max_diff > threshold);
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return x;
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}
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