什么是boost：barrier,如何使用这种boost方法.可以给我一个明确的例子,因为我发现了以下几个例子：
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;
}
解决方法
notify_all,通知等待线程.
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.只有当3个线程在屏障上调用等待功能时,才会输出当前值.
#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(current)));
boost::thread thr3(boost::bind(&thread_fun,boost::ref(current)));
thr1.join();
thr2.join();
thr3.join();
}
