C11 thread Management: Atomic variables & monotone functions

1. Atomic variables

C++11 provides an atomic type of STD::ATOMIC<T>, which can be used as a template parameter, using an atomic variable without the need to protect the variable with a mutex, which is more concise.

For example, if you want to make a counter, use the mutex and use the atomic variable in the following sequence:

//using mutexes structcounter{intvalue;    Std::mutex Mutex; voidincrement () {Std::lock_guard<std::mutex>Lock(mutex); ++value; }    voidDecrement () {Std::lock_guard<std::mutex>Lock(mutex); --value; }    int Get()    {        returnvalue; }};intMain () {return 0;}//using atomic variables#include <atomic>structcounter{std::atomic<int>value; voidincrement () {++value; }    voidDecrement () {--value; }    int Get()    {        returnvalue; }};

2, Call_once/once_flag

Monotonic functions are in a multithreaded environment, to ensure that a function is called only once, such as to initialize an object, and this object can only be initialized once, you can use std::call_once to ensure that the function in a multithreaded environment is called only once. When using Std::call_once, a once_flag is required as an entry for the call_once.

as an entry for the call_once. #include<thread>#include<iostream>#include<mutex>Std::once_flag Flag;voiddo_once () {std::call_once (flag, [] () {std::cout<<"called once."<<Std::endl;});}intMain () {Std::thread T1 (do_once);    Std::thread T2 (do_once);    std::thread t3 (do_once);    T1.join ();    T2.join ();    T3.join (); return 0;}//Output:Called once.

C11 thread Management: Atomic variables & monotone functions