如何讀取鎖定多線程C ++程序

Question

對於下面的帶有openMP的多線程程序，如何防止一個線程將一個線程寫入“ stuff”時其他線程讀取“ stuff”向量？

    vector<int> stuff; //Global vector

    void loop() {
    #pragma omp parallel for
       for(int i=0; i < 8000; i++){
          func(i);
       }
    }

    void func(int& i) {
       vector<int> local(stuff.begin() + i, stuff.end()); //Reading and copying global vector "stuff"

       //Random function calls here

    #pragma omp critical
       stuff.assign(otherstuff.begin(), otherstuff.end()); //Writing to global vector "stuff"
    }

Answer 1

您可以使用互斥鎖來同步對多個線程之間共享的數據的訪問：

#include <mutex>

std::mutex g_stuff_mutex;

vector<int> stuff; //Global vector

void loop() {
#pragma omp parallel for
   for(int i=0; i < 8000; i++){
      func(i);
   }
}

void func(int& i) {
   g_stuff_mutex.lock();
   vector<int> local(stuff.begin() + i, stuff.end()); //Reading and copying global vector "stuff"
   g_stuff_mutex.unlock();

   //Random function calls here

#pragma omp critical
   g_stuff_mutex.lock();
   stuff.assign(otherstuff.begin(), otherstuff.end()); //Writing to global vector "stuff"
   g_stuff_mutex.unlock();

}