c++11 語言級線程

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c++11 語言級線程

 

線程的建立

用std::thread建立線程非常簡單，只需要提供線程函數或函數對象即可，並且可以同時指定線程函數的參數。

#define _CRT_SECURE_NO_WARNINGS#include <iostream>#include <string>#include <chrono>#include <thread>void func1(){    while (true)    {        std::this_thread::sleep_for(std::chrono::milliseconds(3000));        std::cout << __FUNCTION__ << std::endl;    }}void func2(){    while (true)    {        std::this_thread::sleep_for(std::chrono::milliseconds(3000));        std::cout << __FUNCTION__ << std::endl;    }}void func3(int a, char ch, const char *str){    std::this_thread::sleep_for(std::chrono::milliseconds(3000));    std::cout << "a = " << a << std::endl;    std::cout << "ch = " << ch << std::endl;    std::cout << "str = " << str << std::endl;}void mytest(){    std::thread t1(func1); // 子線程1    std::thread t2(func2); // 子線程2    // 線程還可以接收函數的參數    std::thread t3(func3, 1, ‘a‘, "xyz");   //子線程3    std::thread t4(func3, 2, ‘a‘, "abc");   //子線程3    while(true) // 主線程    {        std::this_thread::sleep_for(std::chrono::milliseconds(3000));        std::cout << __FUNCTION__ << std::endl;    }    return;}int main(){    mytest();    system("pause");    return 0;}

 

回收線程資源

std::thread::join等待線程結束（此函數會阻塞），並回收線程資源，如果線程函數有傳回值，傳回值將被忽略。

#define _CRT_SECURE_NO_WARNINGS#include <iostream>#include <string>#include <chrono>#include <thread>void puase_thread(int no, int n){    std::this_thread::sleep_for(std::chrono::seconds(n));    std::cout << "thread-" << no << " pause of " << n << " seconds" << std::endl;}void mytest(){    //std::cout << "Spawning 3 threads..." << std::endl;    std::thread t1(puase_thread, 1, 3);    std::thread t2(puase_thread, 2, 3);    std::thread t3(puase_thread, 3, 3);    std::cout << "Done spawning threads. Now waiting for them to join:" << std::endl;    t1.joinable() ? t1.join() : std::cout << "Thread ID-" << t1.get_id() << " can not join" << std::endl;    t2.joinable() ? t2.join() : std::cout << "Thread ID-" << t2.get_id() << " can not join" << std::endl;    t3.joinable() ? t3.join() : std::cout << "Thread ID-" << t3.get_id() << " can not join" << std::endl;    std::cout << "All threads joined!" << std::endl;    return;}int main(){    mytest();    system("pause");    return 0;}

 

如果不希望線程被阻塞執行，可以調用線程的std::thread::detach（此函數不會阻塞），將線程和線程對象分離，讓線程作為後台線程去執行。

但需要注意的是，detach之後就無法在和線程發生聯絡了，比如detach之後就不能再通過join來等待執行完，線程何時執行完我們也無法控制。

#define _CRT_SECURE_NO_WARNINGS#include <iostream>#include <string>#include <chrono>#include <thread>void puase_thread(int no, int n){    std::this_thread::sleep_for(std::chrono::seconds(n));    std::cout << "thread-" << no << " pause of " << n << " seconds" << std::endl;}void mytest(){    //std::cout << "Spawning 3 threads..." << std::endl;    std::thread t1(puase_thread, 1, 3);    std::thread t2(puase_thread, 2, 3);    std::thread t3(puase_thread, 3, 3);    std::cout << "Done spawning threads. Now waiting for them to join:" << std::endl;    t1.joinable() ? t1.detach() : std::cout << "Thread ID-" << t1.get_id() << " can not detach" << std::endl;    t2.joinable() ? t2.detach() : std::cout << "Thread ID-" << t2.get_id() << " can not detach" << std::endl;    t3.joinable() ? t3.detach() : std::cout << "Thread ID-" << t3.get_id() << " can not detach" << std::endl;    std::cout << "All threads joined!" << std::endl;    return;}int main(){    mytest();    system("pause");    return 0;}

 

擷取線程ID和CPU核心數

#define _CRT_SECURE_NO_WARNINGS#include <iostream>#include <string>#include <chrono>#include <thread>void puase_thread(int n){    std::this_thread::sleep_for(std::chrono::seconds(n));    // std::this_thread::get_id() 擷取線程ID    std::cout << "thread-" << std::this_thread::get_id() << " pause of " << n << " seconds" << std::endl;}void mytest(){    //std::cout << "Spawning 3 threads..." << std::endl;    std::thread t1(puase_thread, 3);    std::thread t2(puase_thread, 3);    std::thread t3(puase_thread, 3);    std::cout << "main id: " << std::this_thread::get_id() << std::endl; // 主線程id    std::cout << "cpu num: " << std::thread::hardware_concurrency() << std::endl; // 擷取cpu核心數，失敗返回0    std::cout << "Done spawning threads. Now waiting for them to join:" << std::endl;    // t1.get_id() // 擷取t1此線程的ID    t1.joinable() ? t1.detach() : std::cout << "Thread ID-" << t1.get_id() << " can not detach" << std::endl;    t2.joinable() ? t2.join() : std::cout << "Thread ID-" << t2.get_id() << " can not join" << std::endl;    t3.joinable() ? t3.join() : std::cout << "Thread ID-" << t3.get_id() << " can not join" << std::endl;    std::cout << "All threads joined!" << std::endl;    return;}int main(){    mytest();    system("pause");    return 0;}

 

c++11 語言級線程