C++11 并发指南二(std::thread 详解)

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std::thread在<thread>头文件中声明，因此使用std::thread时包含<thread>头文件

1、std::thread构造：

1）default——thread()：默认构造函数，创建一个空的thread执行对象

2）initialization——thread(a,b)：初始化构造函数，创建一个thread对象，该对象可被joinable，新产生的线程会调用a函数，函数的参数由b给出

3）copy[deleted]——thread(const thread& ) = delete：拷贝构造函数禁用，意味着thread不可被拷贝构造

4）move——thread(thread&& x)noexcept：构造函数，调用成功后x不代表任何thread执行对象

注意：可被joinable的thread对象必须在它们销毁之前被主线程join，或者将其设置为detached

std::thread各种构造函数例子如下：

#include <iostream>#include <utility>#include <thread>#include <chrono>#include <functional>#include <atomic> void f1(int n){    for (int i = 0; i < 5; ++i) {        std::cout << "Thread 1 executing\n";        ++n;        std::this_thread::sleep_for(std::chrono::milliseconds(10));    }} void f2(int& n){    for (int i = 0; i < 5; ++i) {        std::cout << "Thread 2 executing\n";        ++n;        std::this_thread::sleep_for(std::chrono::milliseconds(10));    }} int main(){    int n = 0;    std::thread t1; // t1 is not a thread    std::thread t2(f1, n + 1); // pass by value    std::thread t3(f2, std::ref(n)); // pass by reference    std::thread t4(std::move(t3)); // t4 is now running f2(). t3 is no longer a thread    t2.join();    t4.join();    std::cout << "Final value of n is " << n << '\n';}

在Mac下打印结果是这样的

TThhrreeaadd  21  executingexecutingTThhrreeaadd  21 executing executingThread 1 executingThread 2 executingTThhrreeaadd  12  eexxeeccuuttiinnggThread 1 executingThread 2 executingFinal value of n is 5

2、Move赋值操作

1）move——thread& operator=(thread&& rhs) noexcept;move赋值操作，如果当前对象不可joinable，需要传递一个右值引用给move赋值操作，如果当前对象可被joinable，则terminate()报错。

2）copy[deleted]——thread& operator=(const thread&) = delete;拷贝赋值操作被禁用，thread对象不可被拷贝

#include <stdio.h>#include <stdlib.h>#include <chrono>#include <iostream>#include <thread>using namespace std;void thread_task(int n){    this_thread::sleep_for(chrono::seconds(n));    cout << "hello thread " << this_thread::get_id() << " Pause " << n << " seconds" << endl;}int main(void){    std::thread threads[5];    cout << "Spawning 5 threads...\n";    for(int i = 0;i < 5; i++)    {        threads[i] = std::thread(thread_task,i+1);    }    cout << "Done spawning threads! Now wait for them to join\n";    for(auto& t : threads)    {        t.join();    }    cout << "All threads joined.\n";        return EXIT_SUCCESS;    }

3、其它成员函数

1）get_id：获取线程ID

2）joinable：检测线程是否可被join

3）join：join线程，会和主线程

4）detach：detach线程，与主线程分离

5）swap：swap线程

6）native_handle：返回native_handle

7）hardware_concurrency[static]：检测硬件并发特性

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