c - OpenMP 运行线程但继续主线程

Question

我正在尝试使用 OpenMP 进行线程处理，因为它是跨平台的。但是我不知道如何在循环运行时并行继续后的代码？它基本上只是并行执行第一个循环，但永远不会进入第二个非并行循环？

int main() {
    #pragma omp parallel 
        while(1) {
            Sleep(4000);
            printf("doing work in thread %d, nthreads %d\n", omp_get_thread_num(), omp_get_num_threads());
        }


    while (1) {
        Sleep(4000);
        printf("Hello from main %d, nthreads %d\n", omp_get_thread_num(), omp_get_num_threads());
    }
}

Answer 1

我认为您可以将其中一个线程作为您的 omp 并行块中的特殊线程

int main() {
    #pragma omp parallel 
        if(omp_get_thread_num()==0){
             while(1) {
                Sleep(4000);
               printf("Hello from main %d, nthreads %d\n", omp_get_thread_num(), omp_get_num_threads());
             }
        }else{
             while(1) {
                Sleep(4000);
                printf("doing work in thread %d, nthreads %d\n", omp_get_thread_num(), omp_get_num_threads());
             }
         }
    }
}

如果没有更多细节，很难判断这对您的情况是否有意义。

您也可以使用 sections .来自这里的示例: http://bisqwit.iki.fi/story/howto/openmp/#Sections :

#pragma omp parallel // starts a new team
{
   //Work0(); // this function would be run by all threads.

   #pragma omp sections // divides the team into sections
   { 
     // everything herein is run only once.
     { Work1(); }
     #pragma omp section
     { Work2();
       Work3(); }
     #pragma omp section
     { Work4(); }
   }

   //Work5(); // this function would be run by all threads.
}

您可以进行嵌套重国有化: OpenMP: What is the benefit of nesting parallelizations?