零度

C++（二）多线程

2020/11/10 C++ 共 2673 字，约 8 分钟

c++多线程学习，包含头文件、异步、睡眠、线程交换、线程移动和线程传参。

1. 线程头文件

C++11 新标准中引入了五个头文件来支持多线程编程

<atomic>：该头文主要声明了两个类, std::atomic 和 std::atomic_flag，另外还声明了一套 C 风格的原子类型和与 C 兼容的原子操作的函数。 <thread>：该头文件主要声明了 std::thread 类，另外 std::this_thread 命名空间也在该头文件中。 <mutex>：该头文件主要声明了与互斥量(mutex)相关的类，包括 std::mutex 系列类，std::lock_guard, std::unique_lock, 以及其他的类型和函数。 <condition_variable>：该头文件主要声明了与条件变量相关的类，包括 std::condition_variable 和 std::condition_variable_any。 <future>：该头文件主要声明了 std::promise, std::package_task 两个 Provider 类，以及 std::future 和 std::shared_future 两个 Future 类，另外还有一些与之相关的类型和函数，std::async() 函数就声明在此头文件中。

2. 线程异步

#include<thread>  
using namespace std;  
void show()  
{  
    cout << "hello cplusplus!" << endl;  
}  
int main()  
{  
    //栈上  
    thread t1(show);   //根据函数初始化执行  
    thread t2(show);  
    thread t3(show);  
    //线程数组  
    thread th[3]{thread(show), thread(show), thread(show)};   
    //堆上  
    thread *pt1(new thread(show));  
    thread *pt2(new thread(show));  
    thread *pt3(new thread(show));  
    //线程指针数组  
    thread *pth(new thread[3]{thread(show), thread(show), thread(show)});  
    return 0;  
}

3. 线程睡眠

#include<thread>  
#include<chrono>  
using namespace std;  
int main()  
{  
    thread th1([]()  
    {  
        //让线程等待3秒  
        this_thread::sleep_for(chrono::seconds(3));  
        //让cpu执行其他空闲的线程  
        this_thread::yield();  
        //线程id  
        cout << this_thread::get_id() << endl;  
    });  
    return 0;  
}

4. 线程交换

#include<thread>  
using namespace std;  
int main()  
{  
    thread t1([]()  
    {  
        cout << "thread1" << endl;  
    });  
    thread t2([]()  
    {  
        cout << "thread2" << endl;  
    });  
    cout << "thread1' id is " << t1.get_id() << endl;  
    cout << "thread2' id is " << t2.get_id() << endl;  

    cout << "swap after:" << endl;  
    swap(t1, t2);//线程交换  
    cout << "thread1' id is " << t1.get_id() << endl;  
    cout << "thread2' id is " << t2.get_id() << endl;  
    return 0;  
}  
运行结果:  
thread1  
thread2  
thread1' id is 4836  
thread2' id is 4724  
swap after:  
thread1' id is 4724  
thread2' id is 4836

5. 线程移动

#include<thread>  
using namespace std;  
int main()  
{  
    thread t1([]()  
    {  
        cout << "thread1" << endl;  
    });  
    cout << "thread1' id is " << t1.get_id() << endl;  
    thread t2 = move(t1);;  
    cout << "thread2' id is " << t2.get_id() << endl;  
    return 0;  
}  
运行结果:  
thread1  
thread1' id is 5620  
thread2' id is 5620

6. 线程传参

#include<thread>  
#include<chrono>  
using namespace std;  
void fun1(int n)  //初始化构造函数  
{  
    cout << "Thread " << n << " executing\n";  
    n += 10;  
    this_thread::sleep_for(chrono::milliseconds(10));  
}  
void fun2(int & n) //拷贝构造函数  
{  
    cout << "Thread " << n << " executing\n";  
    n += 20;  
    this_thread::sleep_for(chrono::milliseconds(10));  
}  
int main()  
{  
    int n = 0;  
    thread t1;               //t1不是一个thread  
    thread t2(fun1, n + 1);  //按照值传递  
    t2.join();  
    cout << "n=" << n << '\n';  
    n = 10;  
    thread t3(fun2, ref(n)); //引用  
    thread t4(move(t3));     //t4执行t3，t3不是thread  
    t4.join();  
    cout << "n=" << n << '\n';  
    return 0;  
}  
运行结果:  
Thread 1 executing  
n=0  
Thread 10 executing  
n=30

文档信息

Search

    Table of Contents