Last blog< C++11 Concurrent Guide I (A Preliminary Study of C++11 Multithreading) > It just mentions the basic usage of std::thread and gives a simple example. This article will introduce the usage of std::thread in some detail.

std::thread is declared in the < thread > header file, so the # include < thread > header file is required when using std::thread.

std::thread construction

• (1). The default constructor creates an empty thread execution object.
• (2) Initialize the constructor and create a thread object, which can be joinable. The newly generated thread will call the fn function, and the parameters of the function are given by args.
• (3) The copy constructor (disabled) means that thread s cannot be copied.
• (4). The move constructor, the move constructor, does not represent any thread ed e x ecution object after a successful call.
• Note: threads that can be joinable must be joined by the main thread or set to detached before they are destroyed.

Examples of std::thread constructors link

#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 " << n << " executing\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';
}

move assignment operation

• (1) The motion assignment operation, if the current object is not joinable, needs to pass a right-value reference (rhs) to the motion assignment operation; if the current object can be joinable, terminate() will report an error.
• (2) Copy assignment is disabled and thread s cannot be copied.

See the following examples:

#include <stdio.h>
#include <stdlib.h>

#include <chrono>    // std::chrono::seconds
#include <iostream>  // std::cout
#include <thread>    // std::thread, std::this_thread::sleep_for

void thread_task(int n) {
    std::this_thread::sleep_for(std::chrono::seconds(n));
    std::cout << "hello thread "
        << std::this_thread::get_id()
        << " paused " << n << " seconds" << std::endl;
}

/*
 * ===  FUNCTION  =========================================================
 *         Name:  main
 *  Description:  program entry routine.
 * ========================================================================
 */
int main(int argc, const char *argv[])
{
    std::thread threads[5];
    std::cout << "Spawning 5 threads...\n";
    for (int i = 0; i < 5; i++) {
        threads[i] = std::thread(thread_task, i + 1);
    }
    std::cout << "Done spawning threads! Now wait for them to join\n";
    for (auto& t: threads) {
        t.join();
    }
    std::cout << "All threads joined.\n";

    return EXIT_SUCCESS;
}

 

 

 

 

Other member functions

• get_id Get the thread ID.
• joinable Check whether threads can be join ed.
• join Join thread.
• detach Detach threads
• swap Swap threads.
• native_handle Return native handle.
• hardware_concurrency [static] Detect hardware concurrency features.