124 lines
3.9 KiB
C
124 lines
3.9 KiB
C
/*
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* MPI version with the matrix subdivided by "lines".
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*/
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#include <stdio.h>
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#include <string.h>
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#include <math.h>
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#include <mpi.h>
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#include "../config.h"
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#include "../utils.h"
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#define TAG_BORDER 0
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#define TAG_MATRIX 1
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float *compute_jacobi(int rank, int numprocs, int n, float init_value, float threshold, borders b, int *iterations) {
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float *complete_x;
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float *x;
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float *new_x;
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float *tmp_x;
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float max_diff, global_max_diff, new_value;
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int i, j;
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int nb = n + 2; // n plus the border
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int rows, rows_to_transmit;
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int receive_pos;
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MPI_Request request_north;
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MPI_Request request_south;
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if (rank == 0) {
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rows = n - (n / numprocs) * (numprocs - 1);
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} else {
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rows = n / numprocs;
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}
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LOG(printf("[Process %d/%d] rows: %d\n", rank, numprocs, rows));
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/* LOG(printf("[Process %d/%d] initializing matrix\n", rank, numprocs)); */
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/* Initialize the matrix */
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x = create_sa_matrix(rows + 2, nb);
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new_x = create_sa_matrix(rows + 2, nb);
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for (i = 0; i < rows + 2; 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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new_x[IDX(nb, i, j)] = init_value;
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}
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}
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/* Initialize boundary regions */
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for (i = 0; i < rows + 2; i++) {
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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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new_x[IDX(nb, i, 0)] = b.west;
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new_x[IDX(nb, i, n + 1)] = b.east;
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}
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if (rank == 0) {
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for (i = 1; i <= n + 1; i++) {
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x[IDX(nb, 0, i)] = b.north;
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new_x[IDX(nb, 0, i)] = b.north;
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}
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}
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if (rank == numprocs - 1){
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for (i = 1; i < n + 1; i++) {
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x[IDX(nb, rows + 1, i)] = b.south;
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new_x[IDX(nb, rows + 1, i)] = b.south;
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}
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}
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/* LOG(printf("[Process %d/%d] matrix initialized\n", rank, numprocs)); */
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/* Iterative refinement of x until values converge */
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*iterations = 0;
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do {
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if (rank != numprocs - 1) {
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// Send south border
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MPI_Isend(&x[IDX(nb, rows, 0)], nb, MPI_FLOAT, rank + 1, TAG_BORDER, MPI_COMM_WORLD, &request_south);
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}
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if (rank != 0) {
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// Send north border
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MPI_Isend(&x[IDX(nb, 1, 0)], nb, MPI_FLOAT, rank - 1, TAG_BORDER, MPI_COMM_WORLD, &request_north);
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}
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max_diff = 0;
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global_max_diff = 0;
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for (i = 1; i <= rows; i++) {
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for (j = 1; j <= n; j++) {
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new_value = 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 = fmaxf(max_diff, fabs(new_value - x[IDX(nb, i, j)]));
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new_x[IDX(nb, i, j)] = new_value;
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}
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}
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tmp_x = new_x;
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new_x = x;
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x = tmp_x;
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if (rank != numprocs - 1) {
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// Receive south border
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MPI_Recv(&x[IDX(nb, rows + 1, 0)], nb, MPI_FLOAT, rank + 1, TAG_BORDER, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
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}
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if (rank != 0) {
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// Receive north border
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MPI_Recv(&x[IDX(nb, 0, 0)], nb, MPI_FLOAT, rank - 1, TAG_BORDER, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
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}
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LOG(printf("[Process %d/%d] max_diff: %f\n", rank, numprocs, max_diff));
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MPI_Allreduce(&max_diff, &global_max_diff, 1, MPI_FLOAT, MPI_MAX, MPI_COMM_WORLD);
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/* LOG(printf("[Process %d/%d] global_max_diff: %f\n", rank, numprocs, global_max_diff)); */
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(*iterations)++;
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} while (global_max_diff > threshold);
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if (rank == 0) {
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complete_x = create_sa_matrix(nb, nb);
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memcpy(complete_x, x, (rows + ((rank == numprocs - 1) ? 2 : 1)) * (nb) * sizeof(float));
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rows_to_transmit = n / numprocs;
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receive_pos = rows + 1;
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for (i = 1; i < numprocs; i++) {
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if (i == numprocs - 1) {
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rows_to_transmit++;
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}
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MPI_Recv(&complete_x[IDX(nb, receive_pos, 0)], rows_to_transmit * (nb), MPI_FLOAT, i, TAG_MATRIX, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
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receive_pos += n / numprocs;
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}
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} else {
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complete_x = NULL;
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rows_to_transmit = rows;
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if (rank == numprocs - 1) {
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rows_to_transmit++;
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}
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MPI_Send(&x[IDX(nb, 1, 0)], rows_to_transmit * (nb), MPI_FLOAT, 0, TAG_MATRIX, MPI_COMM_WORLD);
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}
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return complete_x;
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}
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