如何使用升压屏障 [英] how to use boost barrier

问题描述

什么是升压：障碍，如何使用这种方法提升的。你能给我一个明确的例子，因为我发现下面的例子：

What is boost:barrier, how to use this kind of boost method. Could you give me a clear example since I found the examples on the following:

    bool wait()
    {
        boost::mutex::scoped_lock lock(m_mutex);
        unsigned int gen = m_generation;

        if (--m_count == 0)
        {
            m_generation++;
            m_count = m_threshold;
            m_cond.notify_all();
            return true;
        }

        while (gen == m_generation)
            m_cond.wait(lock);
        return false;
    }

在上面的codeS：m_cond.notify_all（）;二是进入其他等待线程？
你能告诉我关于明确屏障功能？谢谢你。

In the above codes: m_cond.notify_all();is to enter into other waiting threads? Could you tell me clearly about barrier functionality? Thank you.

推荐答案

notify_all，通知等待线程。

notify_all, notified awaiting threads.

一个障碍是一个简单的概念。也称为集合，它是一个
  多线程之间的同步点。该屏障
  配置成用于螺纹（n）的特定号码，并作为线程
  到达他们必须等待，直到所有n个线程已经到达屏障。
  一旦第n线程已到达屏障，所有等待的线程
  可以继续，并且阻挡复位。

A barrier is a simple concept. Also known as a rendezvous, it is a synchronization point between multiple threads. The barrier is configured for a particular number of threads (n), and as threads reach the barrier they must wait until all n threads have arrived. Once the n-th thread has reached the barrier, all the waiting threads can proceed, and the barrier is reset.

简单的例子。电流值时，3线程调用的屏障等待功能仅所输出的。

Simple example. value of the current will be outputed only when 3 threads call wait function on barrier.

#include <boost/thread.hpp>
#include <boost/thread/barrier.hpp>
#include <boost/bind.hpp>
#include <boost/atomic.hpp>

boost::mutex io_mutex;

void thread_fun(boost::barrier& cur_barier, boost::atomic<int>& current)
{
    ++current;
    cur_barier.wait();
    boost::lock_guard<boost::mutex> locker(io_mutex);
    std::cout << current << std::endl;
}

int main()
{
    boost::barrier bar(3);
    boost::atomic<int> current(0);
    boost::thread thr1(boost::bind(&thread_fun, boost::ref(bar), boost::ref(current)));
    boost::thread thr2(boost::bind(&thread_fun, boost::ref(bar), boost::ref(current)));
    boost::thread thr3(boost::bind(&thread_fun, boost::ref(bar), boost::ref(current)));
    thr1.join();
    thr2.join();
    thr3.join();
}

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