版权声明:本文为博主原创文章,未经博主允许不得转载。博客主页:http://blog.csdn.net/u013390476 https://blog.csdn.net/u013390476/article/details/52067321
前言
multi-threading以及lambda是C++11的重要升级,下面的经典的生产者-消费者的代码,既使用了C++11的multi-threading相关的库, 又使用了lambda。代码中有注释,应该比较详细。
Talk is cheap show me the code
#include <iostream>
#include <queue>
#include <thread>
#include <mutex>
#include <condition_variable>
using namespace std;
mutex mtx;
condition_variable produce, consume; // 条件变量是一种同步机制,要和mutex以及lock一起使用
queue<int> q; // shared value by producers and consumers, which is the critical section
int maxSize = 20;
void consumer()
{
while (true)
{
this_thread::sleep_for(chrono::milliseconds(1000));
unique_lock<mutex> lck(mtx); // RAII,程序运行到此block的外面(进入下一个while循环之前),资源(内存)自动释放
consume.wait(lck, [] {return q.size() != 0; }); // wait(block) consumer until q.size() != 0 is true
cout << "consumer " << this_thread::get_id() << ": ";
q.pop();
cout << q.size() << '\n';
produce.notify_all(); // nodity(wake up) producer when q.size() != maxSize is true
}
}
void producer(int id)
{
while (true)
{
this_thread::sleep_for(chrono::milliseconds(900)); // producer is a little faster than consumer
unique_lock<mutex> lck(mtx);
produce.wait(lck, [] {return q.size() != maxSize; }); // wait(block) producer until q.size() != maxSize is true
cout << "-> producer " << this_thread::get_id() << ": ";
q.push(id);
cout << q.size() << '\n';
consume.notify_all(); // notify(wake up) consumer when q.size() != 0 is true
}
}
int main()
{
thread consumers[2], producers[2];
// spawn 2 consumers and 2 producers:
for (int i = 0; i < 2; ++i)
{
consumers[i] = thread(consumer);
producers[i] = thread(producer, i + 1);
}
// join them back: (in this program, never join...)
for (int i = 0; i < 2; ++i)
{
producers[i].join();
consumers[i].join();
}
system("pause");
return 0;
}
扩展阅读
为什么条件变量和互斥锁要在一起使用。这篇博客使用类Unix操作系统的POSIX multithreading,来讲解条件变量(condition variable) 为什么,以及怎么和互斥锁(mutex and lock)一起配套使用。
Last update: 2017/7/27