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main.cpp

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#include <iostream>#include <vector>#include <chrono>#include <functional>#include "ThreadPool.h"#include <omp.h>class CA{    int a = 1;    int b = 2;public:    int Max(int a, int b)    {        return a > b ? a : b;    }#if 0    double Max(int a)    {        return a;    }#endif    int Sum(int a, int b)    {        return a + b;    }};int main(){    ThreadPool pool(4);    std::vector< std::future<int> > results;    for (int i = 0; i < 16; ++i) {        results.emplace_back(            pool.enqueue([i] {        //    std::cout << "hello " << i << std::endl;        //    std::this_thread::sleep_for(std::chrono::seconds(1));            return i*i;        })            );    }    for (auto && result : results){        //std::cout << result.get() << ‘ ‘;        std::cout <<"sync"<< \n;    }//同步:要等这里结束,才能往下执行,    std::cout << "~~main~~" << std::endl;    //成员函数不能有重名的(重载)。    CA testA;    //mem_fn    std::future<int> fe = pool.enqueue(std::mem_fn(&CA::Max), testA, 3, 99999);    //bind    using namespace std::placeholders;    std::future<int> fl = pool.enqueue(std::bind(&CA::Sum,&testA,_1,_2),3,99);    std::cout << fl.get()  << std::endl;    std::cout << fe.get()  << std::endl;    return 0;}
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ThreadPool.h

 

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#ifndef THREAD_POOL_H#define THREAD_POOL_H#include <vector>#include <queue>#include <memory>#include <thread>#include <mutex>#include <condition_variable>#include <future>#include <functional>#include <stdexcept>#include <stdio.h>#include <chrono>             // std::chrono::seconds//线程池线程空闲自动退出时间间隔 ,5分钟const int  THREAD_WAIT_TIME_OUT = 10;  //10 sclass ThreadPool {public:    ThreadPool(size_t);    template<class F, class... Args>    auto enqueue(F&& f, Args&&... args)        ->//std::future<typename std::result_of<F(Args...)>::type>;        //std::future < decltype(f(std::forward<Args>(args...))) > ;    std::future < decltype(f(args...)) > ;    void threadFun();    ~ThreadPool();    private:    // need to keep track of threads so we can join them    std::vector< std::thread > workers;    // the task queue    std::queue< std::function<void()> > tasks;    // synchronization    std::mutex queue_mutex;    std::condition_variable condition;    bool stop;};// the constructor just launches some amount of workersinline ThreadPool::ThreadPool(size_t threads)    : stop(false){    for (size_t i = 0; i<threads; ++i)        workers.emplace_back(&ThreadPool::threadFun, this);}// add new work item to the pooltemplate<class F, class... Args>auto ThreadPool::enqueue(F&& f, Args&&... args)->//std::future<decltype(f(std::forward<Args>(args...)))>//std::future<typename std::result_of<F(Args...)>::type>std::future<decltype(f(args...))>{    //  using return_type = typename std::result_of<F(Args...)>::type;    using return_type = decltype(f(args...));    auto task = std::make_shared< std::packaged_task<return_type()> >(        std::bind(std::forward<F>(f), std::forward<Args>(args)...)        );        std::future<return_type> res = task->get_future();    {        std::unique_lock<std::mutex> lock(queue_mutex);        // don‘t allow enqueueing after stopping the pool        if (stop)            throw std::runtime_error("enqueue on stopped ThreadPool");        tasks.emplace([task]{ (*task)(); });        //tasks.emplace([task]{ std::move(*task)(); });    }    condition.notify_one();    return res;}void ThreadPool::threadFun()  {    for (;;)    {        std::function<void()> task;        {            //std::unique_lock<std::mutex> lock(this->queue_mutex);            std::unique_lock<std::mutex> lock(queue_mutex);            //当条件为假的时候,才阻塞            //同时为假才阻塞,stop为false ,并且任务为空            this->condition.wait(lock,                [this]{ return this->stop || !this->tasks.empty(); });            if (this->stop && this->tasks.empty())            {                printf("@@--%d--@@\n", std::this_thread::get_id());                if (this->condition.wait_for(lock, std::chrono::seconds(THREAD_WAIT_TIME_OUT)) == std::cv_status::timeout)                    // printf("@@--%d--@@\n",std::this_thread::get_id());                    break;                else                    continue;            }            task = std::move(this->tasks.front());            this->tasks.pop();        }        task();    }}// the destructor joins all threadsinline ThreadPool::~ThreadPool(){    {        std::unique_lock<std::mutex> lock(queue_mutex);        stop = true;    }    condition.notify_all();    for (std::thread &worker : workers)        worker.join();}#endif
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