M-M_omp.c

/**
 * @author Rohin Arora
 * @email rohinarora07@gmail.com
 * @create date 2020-02-25
 * @modify date 2020-02-25
 *
 * Matrix multiplication with OMP. Current system has 12 threads
 */

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <omp.h>
#define M 512
#define NUM_THREADS 12

double CLOCK()
{
    struct timespec t;
    clock_gettime(CLOCK_MONOTONIC, &t);
    return (t.tv_sec * 1000) + (t.tv_nsec * 1e-6);
}

int main(int argc, char **argv)
{
    omp_set_num_threads(NUM_THREADS);
    int i, j, k, jj, kk, en;
    double start, finish, total, sum;
    float a[M][M], b[M][M], c[M][M];

    /* Set the seed for the random number generators for the data */
    srand(145);

    /* Initialize a, b and c */
    for (i = 0; i < M; i++)
        for (j = 0; j < M; j++)
            a[i][j] = (float)rand() / (float)RAND_MAX;

    for (i = 0; i < M; i++)
        for (j = 0; j < M; j++)
            b[i][j] = (float)rand() / (float)RAND_MAX;

    for (i = 0; i < M; i++)
        for (j = 0; j < M; j++)
            c[i][j] = 0.;

    /* Start timing */
    start = CLOCK();

    /* This is the only portion of the code you should modify to improve performance. */
    double x = 0;
#pragma omp parallel for private(x, i, j, k)
    {
        for (i = 0; i < M; i++)
        {
            for (j = 0; j < M; j++)
            {
                x = 0;
                for (k = 0; k < M; k++)
                {
                    x += a[i][k] * b[k][j];
                }
                c[i][j] = x;
            }
        }
    }

    finish = CLOCK();
    /* End timing */
    total = finish - start;
    printf("Time for the loop = %4.2f milliseconds\n", total);
    printf("Element %d,%d = %f\n", 0, 0, c[0][0]);
    printf("Element %d,%d = %f\n", 63, 63, c[63][63]);
    printf("Element %d,%d = %f\n", 511, 511, c[511][511]);
    return 0;
}