omp_multi_matrice.cpp

#include <cstdlib>
#include <ctime>
#include <random>
#include <omp.h>

const int limit = 10;

int main(int argc, char* argv[]) {

    int n = strtol(argv[1], NULL, 10);
    int num_thrs = strtol(argv[2], NULL, 10);

    int i, j, k;
    int* A = new int[n * n];
    int* B = new int[n * n];
    int* C = new int[n * n]();

    srand(static_cast<unsigned>(time(0)));
    for (i = 0; i < n; i++) {
        for (j = 0; j < n; j++) {
            A[i * n + j] = rand() % limit;
            B[i * n + j] = rand() % limit;
        }
    }
    
    double start, end;
    start = omp_get_wtime();
    
#   pragma omp parallel for collapse(2) default(none) shared(A, B, C, n) private(k) num_threads(num_thrs)
    for (i = 0; i < n; i++) {
        for (j = 0; j < n; j++) {
            for (k = 0; k < n; k++) {
                C[i * n + j] += A[i * n + k] * B[k * n + j];
            }
        }
    }
    
    end = omp_get_wtime();

    double duration = end - start;

    printf("cost time: \t%lfs\n", duration);

    delete[] A;
    delete[] B;
    delete[] C;

    return 0;
}

// ./omp_multi_matrice <the amount of data> <the number of the threads>