C/C++在Linux上的多线程

简介

        在集群上每个计算节点有三四十个核心，往往使用MPI对任务进行并行计算，计算资源平均分布在多个节点的多个CPU核心上。为了充分利用计算节点剩余的核心，可以将任务再次细分，在MPI多进程的基础上每个进程使用多线程调用空闲核心完成计算。

多线程

源代码

#include <iostream>
#include <thread>
#include <pthread.h>

using namespace std;

// 多线程之pthread_create的参数结构体
typedef struct
{
        int myid;
        double *matrix;
        char name[1024];
}THREADPARAM, *PTHREADPARAM;

// 多线程之std::thread的测试函数
void func(int myid)
{
        std::cout << "this is func!" << endl;
        // 打印线程ID
        std::cout << "myid is : " << myid << "   this thread id is " << std::this_thread::get_id() << endl;
}

// 多线程之pthread_create的测试函数，返回值为void*，输入参数的结构体为void*
void* func2(void* pthreadparam)
{
        // 解析参数
        std::cout << "this is func2!       " << "thread id is : " << ((PTHREADPARAM)pthreadparam)->myid <<endl;
}

int main()
{
        std::cout << "***************** std::thread start ***************** " << endl;

        // 打印线程ID
        std::cout << "main thread id = " << std::this_thread::get_id() << std::endl;
        // 打印线程总数，即CPU逻辑核心数量
        std::cout << "all threads number = " << std::thread::hardware_concurrency() << std::endl;

        // 创建线程 std::thread 变量名 (调用函数名，函数所需参数)
        std::thread thread1 (func, 1);
        std::thread thread2 (func, 2);
        std::thread thread3 (func, 3);
        std::thread thread4 (func, 4);

        // 阻塞线程(等待执行完毕，释放资源)
        thread1.join();
        thread2.join();
        thread3.join();
        thread4.join();

        std::cout << "***************** std::thread end ***************** " << endl;

        std::cout << "***************** pthread start ***************** " << endl;

        // 子线程数量
        const int THREADNUM = 32;
        // 子线程所需参数       
        THREADPARAM threadparam[THREADNUM];
        // 创建子线程
        pthread_t pt[THREADNUM];

        // 为子线程分配任务
        for (int i = 0; i < THREADNUM; i++)
        {
                // 子线程参数结构体初始化
                threadparam[i].myid = i;
                // 启动子线程
                pthread_create(&pt[i], NULL, func2, (void*)(&threadparam[i]));
        }

        // 阻塞子线程
        for (int i = 0; i < THREADNUM; i++)
        {
                pthread_join(pt[i], NULL);
        }

        std::cout << "***************** pthread end ***************** " << endl;

        return 0;
}

编译

g++ -o thread-l.out -std=c++11 -lpthread thread-l.cpp