40.多线程实现矩阵相乘

单线程运行时间:

多线程运行时间;

代码:

#include <stdlib.h>
#include <stdio.h>
#include <process.h>
#include <Windows.h>
#include <time.h>

#define N 1000

double M1[N][N] = { 0 };
double M2[N][N] = { 0 };
double res[N][N] = { 0 };

//多线程函数,p表示行
void process(void *p)
{
    int *row = (int *)p;

    //M2每一列
    for (int j = 0; j < N; j++)
    {
        int tmp = 0;
        //遍历M2某列的元素
        for (int k = 0; k < N; k++)
        {
            tmp += M1[*row][k] * M2[k][j];
        }
        res[*row][j] = tmp;
    }
}

//初始化矩阵
void init(double num[N][N])
{
    for (int i = 0; i < N; i++)
    {
        for (int j = 0; j < N; j++)
        {
            num[i][j] = rand() % 5 ;
        }
    }
}

//显示矩阵
void show(double num[N][N])
{
    for (int i = 0; i < N; i++)
    {
        for (int j = 0; j < N; j++)
        {
            printf("%.2f     ", num[i][j]);
        }
        printf("\n");
    }
}

void main()
{
    //统计时间
    clock_t start, finish;
    double duration = 0;

    start = clock();
    init(M1);
    init(M2);
    //show(M1);
    //show(M2);
    int num1 = 0;
    
    ////多线程
    for (int i = 0; i < N; i++)
    {
        HANDLE hd = (HANDLE)_beginthread(process, 0,  &i);
        //WaitForSingleObject(hd, INFINITE);
    }

    //单线程
    /*for (int i = 0; i < N; i++)
    {
        process(&i);
    }*/

    finish = clock();
    duration = (double)(finish - start) / CLOCKS_PER_SEC;
    printf("%f seconds\n", duration);

    system("pause");
}