使用 OpenMP 並行 hello world

以下 C 程式碼使用 OpenMP 並行程式設計模型使用多個執行緒將執行緒 ID 和執行緒數寫入 stdout。

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

int main ()
{
    #pragma omp parallel
    {   
        // ID of the thread in the current team
        int thread_id = omp_get_thread_num();
        // Number of threads in the current team
        int nthreads = omp_get_num_threads();

        printf("I'm thread %d out of %d threads.\n", thread_id, nthreads);
    }
    return 0;
}

在 Fortran 90+中，等效程式如下所示：

program Hello
  use omp_lib, only: omp_get_thread_num, omp_get_num_threads

  implicit none

  integer::thread_id
  integer::nthreads

  !$omp parallel private( thread_id, nthreads )

  ! ID of the thread in the current team
  thread_id = omp_get_thread_num()
  ! Number of threads in the current team
  nthreads = omp_get_num_threads()

  print *, "I'm thread", thread_id, "out of", nthreads, "threads."
  !$omp end parallel
end program Hello