知识体系

thread

C++ thread中最常用的两个函数是join和detach，怎么选择呢，简单来说，如果希望等待线程结束，用join，如果希望异步执行，且不等待执行结果，那么就用detach；thread_local可以简单理解为一个线程级别的全局变量；线程id在调试多线程程序时是非常有用的东西；

C++11本身没有提供线程池；可以参考第三方的实现：https://github.com/progschj/ThreadPool

#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