c++11使用atomic多线程同步3种方法-白红宇

c++11使用atomic多线程同步3种方法

阅读量：4092 次

发布时间：2019-05-25

本文共 1692 字，大约阅读时间需要 5 分钟。

// 使用CAS实现多线程无锁访问共享变量，达到线程同步# include 
   
    # include 
    
     # include 
     
      # include 
      
       using namespace std;std::atomic
       
         var(0);void add() {
       int expect = var;    while (!atomic_compare_exchange_weak(&var, &expect, var + 1));}int main(int argc, char *argv[]) {
       int count = 2000;    std::thread threads[count];    for (int i = 0; i < count; ++i) threads[i] = std::thread(add);    for (int i = 0; i < count; ++i) threads[i].join();    cout << var << endl; // var 为 2000，无误！！    return 0;}

// 使用原子数据类型的原子方法操作，达到同步线程# include 
   
    # include 
    
     # include 
     
      # include 
      
       using namespace std;std::atomic
       
         var(0);void add() {
       var.fetch_add(1);    // cout << std::boolalpha ;    // cout << "is_lock_free:" << var.is_lock_free() << endl;  // true}int main(int argc, char *argv[]) {
       int count = 2000;    std::thread threads[count]; // default-constructed threads    for (int i = 0; i < count; ++i) threads[i] = std::thread(add);    for (int i = 0; i < count; ++i) threads[i].join();    cout << var << endl;    return 0;}

// 使用RAII的mutex，同步线程# include 
   
    # include 
    
     # include 
     
      # include 
      
       using namespace std;std::mutex mtx;void add(int *var) {
       std::lock_guard
       
         l(mtx);    (*var)++;}int main(int argc, char *argv[]) {
       int count = 2000;    std::thread threads[count]; // default-constructed threads    int *var = new int [1];    for (int i = 0; i < count; ++i) threads[i] = std::thread(add, var);    for (int i = 0; i < count; ++i) threads[i].join();    cout << *var << endl;    return 0;}