parallel

// CPP Program to thread_solverply two matrix using pthreads
#include <bits/stdc++.h>
#include <chrono>

using namespace std;
using namespace std::chrono;
// maximum size of matrix
#define MAX 4

// maximum number of threads
#define MAX_THREAD 4


int MX = 100;
int **a, **b, **c;
int core = 0;
int n;
pthread_t threads[MAX_THREAD];

void print_array(int **a) {
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < n; j++)
        {
            cout << a[i][j] << " ";
        }
        cout << endl;
    }

}


void* thread_solver(void* arg) {
    for (int i = n*core/4; i < (core+1)*n/4; i++)
    {
        for (int j = 0; j < n; j++)
            for (int k = 0; k < n; k++)
                c[i][j] += a[i][k] * b[k][j];
    }
    core++;
}


// Driver Code
int main(int argc, char **argv)
{
    time_t start, end;
    n = atoi(argv[1]);
    a = (int**)malloc(n*sizeof(int*));
    b = (int**)malloc(n*sizeof(int*));
    c = (int**)malloc(n*sizeof(int*));

    for (int i = 0; i < n; i++) {
        a[i] = (int*)malloc(n*sizeof(int));
        b[i] = (int*)malloc(n*sizeof(int));
        c[i] = (int*)malloc(n*sizeof(int));
        for (int j = 0; j < n; j++) {
            a[i][j] = rand() % MX;
            b[i][j] = rand() % MX;
        }
    }
    //cout << "A :" << endl;
    //print_array(a);
    //cout << endl;
    //cout << "B :" << endl;
    //print_array(b);
    //cout << endl;


    time(&start);
    clock_t st, ed;
    st = clock();
    clock_t tic = clock();
    auto strt = high_resolution_clock::now();
    for (int i = 0; i < MAX_THREAD; i++) {
        int* p;
        pthread_create(&threads[i], NULL, thread_solver, (void*)(p));
    }

    for (int i = 0; i < MAX_THREAD; i++)
        pthread_join(threads[i], NULL);

    //print_array(c);
    auto stop = high_resolution_clock::now() ;
    auto duration = duration_cast<microseconds>(stop - strt);

    clock_t toc = clock();
    ed = clock();
    time(&end);
    auto x =double(ed-st)/double(CLOCKS_PER_SEC);
    free(a);
    free(b);
    free(c);
    cout << "n : " << n << " time : " << duration.count() << endl;

}