C++ 線程池實作

實作

github上大神的代碼:

https://github.com/progschj/ThreadPool

隻有一個檔案，不到100行啊。

ThreadPool.h

#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>

class 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>;
    ~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 workers
inline ThreadPool::ThreadPool(size_t threads)
    : stop(false)
{
    for (size_t i = 0; i < threads; ++i)
        workers.emplace_back(
            [this]
            {
                for (;;)
                {
                    std::function<void()> task;

                    {
                        std::unique_lock<std::mutex> lock(this->queue_mutex);
                        this->condition.wait(lock,
                            [this] { return this->stop || !this->tasks.empty(); });
                        if (this->stop && this->tasks.empty())
                            return;
                        task = std::move(this->tasks.front());
                        this->tasks.pop();
                    }

                    task();
                }
            }
            );
}

// add new work item to the pool
template<class F, class... Args>
auto ThreadPool::enqueue(F&& f, Args&&... args)
-> std::future<typename std::result_of<F(Args...)>::type>
{
    using return_type = typename std::result_of<F(Args...)>::type;

    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)(); });
    }
    condition.notify_one();
    return res;
}

// the destructor joins all threads
inline ThreadPool::~ThreadPool()
{
    {
        std::unique_lock<std::mutex> lock(queue_mutex);
        stop = true;
    }
    condition.notify_all();
    for (std::thread& worker : workers)
        worker.join();
}

#endif

           

大神的例子

// create thread pool with 4 worker threads
ThreadPool pool(4);

// enqueue and store future
auto result = pool.enqueue([](int answer) { return answer; }, 42);

// get result from future
std::cout << result.get() << std::endl;
           

我的使用驗證測試

#include "ThreadPool.h"
class Test
{
public:
    int add(int a, int b) { std::cout << a << std::endl; return a + b; }
};

//const string G_GCONFIG = "../config/config.ini";
int main(int argc, char** argv)
{
    // create thread pool with 4 worker threads
    ThreadPool pool(4);
    Test tt;
	
	//綁定對象方法
    auto result = pool.enqueue(&test::add,&tt,3,4);
    auto result1 = pool.enqueue(&test::add, &tt, 32, 4);
    auto result2 = pool.enqueue(&test::add, &tt, 33, 4);
    auto result3 = pool.enqueue(&test::add, &tt, 34, 4);
    auto result4 = pool.enqueue(&test::add, &tt, 35, 4);

    // get result from future
    std::cout << result.get() << std::endl;
    getchar();
    return 0;