是否有使用线程池的std :: async实现? [英] Is there an implementation of std::async which uses thread pool?

问题描述

标准函数 std :: async :

模板函数async异步运行函数f(可能在单独的线程中，该线程可能是线程池的一部分)，并返回std :: future，最终将保留该函数调用的结果.

The template function async runs the function f asynchronously (potentially in a separate thread which may be part of a thread pool) and returns a std::future that will eventually hold the result of that function call.

有两个启动策略 std :: launch :: async和std :: launch :: deferred .在我的编译器( GCC 6.2 )标准库的实现中，第一个总是创建一个新线程，第二个总是在调用线程上进行惰性求值.默认情况下，使用std::launch::deferred.

There is two launch polices std::launch::async and std::launch::deferred. In my compiler's (GCC 6.2) standard library impelmentation, the first one always creates a new thread and the second one does lazy evaluation on the calling thread. By default std::launch::deferred is used.

是否有一些实现使用线程池，该线程池的大小等于指定std::launch::async时可用的硬件线程，以避免在递归算法中使用std::async时创建多个线程?

Is there some implementation which uses thread pool with size equal to the hardware threads available when std::launch::async is specified to avoid creating two many threads when std::async is used in recursive algorithm?

推荐答案

我正在使用这种方法

class ThreadPool
{
public:
    ThreadPool(size_t n) 
        : work_(io_service_)
    {
        AddThreads(n);
    }
    /**
     * \brief Adds \a n threads to this thread pool
     * \param n - count of threads to add
     */
    void AddThreads(size_t n)
    {
        for (size_t i = 0; i < n; i++)
            threads_.create_thread(boost::bind(&boost::asio::io_service::run, &io_service_));
    }
    /**
     * \brief Count of thread in pool
     * \return number
     */
    size_t Size() const
    {
        return threads_.size();
    }
    ~ThreadPool()
    {
        io_service_.stop();
        threads_.join_all();
    }

    /**
     * \brief Perform task \a pt. see io_service::post
     * \tparam T - type with operator() defined
     * \param pt - functional object to execute
     */
    template <class T>
    void post(std::shared_ptr<T> &pt)
    {
        io_service_.post(boost::bind(&T::operator(), pt));
    }

    /**
     * \brief Perform task \a pt. see io_service::dispatch
     * \tparam T - type with operator() defined
     * \param pt - functional object to execute
     */
    template <class T>
    void dispatch(std::shared_ptr<T> &pt)
    {
        io_service_.dispatch(boost::bind(&T::operator(), pt));
    }

private:
    boost::thread_group threads_;
    boost::asio::io_service io_service_; 
    boost::asio::io_service::work work_;
};

dispatch是asynk(..., async); post是asynk(..., deferred);

这篇关于是否有使用线程池的std :: async实现?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！