26.多线程

#include <Windows.h>

DWORD WINAPI my_message(void *p)
{
    MessageBoxA(0, "hello", "china", 0);

    return 0;
}

void main()
{
    HANDLE hthread;
    DWORD threadid;//保存线程的编号

    for (int i = 0; i < 5; i++)
    {
        hthread = CreateThread(
            NULL,//安全属性
            NULL,//堆栈大小
            my_message,//线程的入口点
            NULL,//函数的参数
            0,//立即执行
            &threadid);//保存线程的编号

        WaitForSingleObject(hthread, INFINITE);//等待 执行完再执行下一个
    }

    system("pause");
}

 另一种方法实现多线程

#define _CRT_SECURE_NO_WARNINGS
#include <stdlib.h>
#include <stdio.h>
#include <process.h>
#include <Windows.h>
#include <string.h>

//多线程函数
void pro(void *p)
{
    char str[100];
    int *num = (int *)p;
    sprintf(str, "%d", *num);
    MessageBoxA(0, str, "多线程", 1);
}

void main()
{
    for (int i = 0; i < 10; i++)
    {
        HANDLE hd = (HANDLE)_beginthread(pro, 0, &i);
        //WaitForSingleObject(hd,INFINITE);
        //等待当前线程执行完再执行下一个线程
    }

    system("pause");
}

 多线程切割实现数值计算

#define _CRT_SECURE_NO_WARNINGS
#include <stdlib.h>
#include <stdio.h>
#include <process.h>
#include <Windows.h>
#include <time.h>
#define N 1000

//每个线程的信息
struct Myinfo
{
    int id;//线程编号
    int *pstart;//开始地址
    int length;//长度
    int sum;//存储数据的和
};

//多线程函数
void add(void *p)
{
    struct Myinfo *pinfo = (struct Myinfo *)p;
    //根据线程信息求出相应的值
    for (int i = 0; i < pinfo->length; i++)
    {
        pinfo->sum += pinfo->pstart[i];
    }
    printf("线程%d计算结果%d
", pinfo->id, pinfo->sum);
}


void main()
{
    //初始化随机数种子
    time_t ts;
    unsigned int num = time(&ts);
    srand(num);
    int data[N] = { 0 };
    //随机初始化数组
    for (int i = 0; i < N; i++)
    {
        data[i] = rand() % 1000;
    }

    

    struct Myinfo info[8] = { 0 };

    //开启八个进程
    for (int i = 0; i < 8; i++)
    {
        info[i].id = i;
        info[i].length = N / 8;
        info[i].sum = 0;
        info[i].pstart = data + i*N / 8;
        _beginthread(add, 0, &info[i]);
    }

    //求出总和
    Sleep(1);
    int lastsum = 0;
    for (int i = 0; i < 8; i++)
    {
        lastsum += info[i].sum;
    }

    printf("多线程总结果;%d
", lastsum);
    system("pause");
}