#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <iostream>
#include <pthread.h>

const int N = 500;
const int step = 10;
int n;
int A[N][N];
int B[N][N];
int C[N][N];
double t1, t2, t3, t4;
#define num_threads 8

void* task_code(void* param)
{
    int num, i, j;
    num = (*((int*)param));

    for (i = num * n / num_threads; i < (num + 1) * n / num_threads; i++)
        for (j = 0; j < n; j++)
            C[i][j] = A[i][j] * B[i][j];
    return NULL;
}

double mtime()
{
    struct timeval t;
    gettimeofday(&t, NULL);
    double mt = (double)t.tv_usec;
    return mt / 1000000;
}

int main(void)
{
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < N; j++) {
            A[i][j] = rand() % 1000;
            B[i][j] = rand() % 1000;
            C[i][j] = 0;
        }
    }

    for (n = step; n <= N; n += step) {
        pthread_t threads[num_threads];
        int thread_args[num_threads];
        int rc, i;

        // ||
        t3 = mtime();
        for (i = 0; i < num_threads; ++i) {
            thread_args[i] = i;
            rc = pthread_create(&threads[i], NULL, task_code, (void*)&thread_args[i]);
            assert(0 == rc);
        }
        for (i = 0; i < num_threads; ++i) {
            rc = pthread_join(threads[i], NULL);
            assert(0 == rc);
        }
        t4 = mtime();

        // default
        t1 = mtime();
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n; j++) {
                C[i][j] = A[i][j] * B[i][j];
            }
        }
        t2 = mtime();

        printf("--------------------------------------------\n");
        printf("n = %d\n", n);
        printf("p = %d\n", num_threads);
        printf("T1 = %lf(s)\n", (t4 - t3));
        printf("Tp = %lf(s)\n", (t2 - t1));
        printf("S = %lf\n", (t2 - t1) / (t4 - t3));
        printf("E = %lf \n", (t2 - t1) / (t4 - t3) / num_threads);
        printf("t1 = %f \n", t1);
        printf("t2 = %f \n", t2);
        printf("t3 = %f \n", t3);
        printf("t4 = %f \n", t4);
    }
    return EXIT_SUCCESS;
}



#define WIN32_LEAN_AND_MEAN
#include <Windows.h>
#include <stdint.h> // portable: uint64_t   MSVC: __int64

// MSVC defines this in winsock2.h!?
typedef struct timeval {
    long tv_sec;
    long tv_usec;
} timeval;