C ++ concurrent programming basics

A thread library in C ++ native_handle()member functions by using platform-specific API allows direct manipulation of the underlying implementation.

In order to run concurrently function requires the use of specific functions, and objects to manage the various threads. C ++ header file It provides classes and functions management thread

A simple Hello, Concurrent World program:

#include <iostream>
#include <thread>  //①
void hello()  //②
{
  std::cout << "Hello Concurrent World\n";
}
int main()
{
  std::thread t(hello);  //③
  t.join();  //④
}

Which calls the method std::thread, it is still visible std domain; simultaneously joinfunction is to ensure that tthread of execution after the completion of mainthe main thread until the end.

Start a thread

Thread starts when the thread object is created, namely construction thread std::threadwill start object. That is to say we need to set a shared variable only mutual control between threads can be achieved.

• Method three constructs:

std::thread my_thread(background_task);     // 1
std::thread my_thread((background_task())); // 2
std::thread my_thread{background_task()};   // 3

• After starting the thread, is a clear need to wait for the end of the thread (join style), or let it run autonomously (separate)

t.detach(); //(分离式),new和current线程无关
t.join();   //(加入式),阻塞current线程，执行新线程

• Modify variables between threads is required std::ref()to convert the data to reference data:

std::thread t(update_data_for_widget,w,std::ref(data));

Synchronization of data security

std::mutex mt;
void addmethod(int a)
{
    mt.lock();
    addprocessing(...);
    mt.unlock();
}
void deletemethod(int a)
{
    mt.lock();
    deleteprocessing(...);
    mt.unlock();
}

Use unique_lock or lock_guard achieve locked.

std::mutex mt;
void addmethod(int a)
{
    std::unique_lock<std::mutex> lock(mt);
    addprocessing(...);
}
void deletemethod(int a)
{
    std::unique_lock<std::mutex> l(mt);
    deleteprocessing(...);
}