c++ - #pragma omp parallel num_threads 不工作

Question

    #include<omp.h>
    #include<stdio.h>
    #include<stdlib.h>

    void main(int argc, int *argv[]){


   #pragma omp parallel num_threads(3)
   {

    int tid = omp_get_thread_num();
    printf("Hello world from thread = %d \n",tid);
    if(tid == 0){
        int nthreads = omp_get_num_threads();
        printf("Number of threads = %d\n",nthreads);
    }
   }

  }

我正在学习OpenMP，我不明白为什么我指定了线程数3，它只执行一个线程？程序输出:

   Hello world from thread = 0
   Number of threads = 1

Answer 1

您需要使用-fopenmp 编译您的程序。

g++ a.cc -fopenmp