我正在嘗試在debian 7上使用openmpi和mpirun運行此示例hello world程序。#include <stdio.h>#include <mpi/mpi.h>int main (int argc, char **argv) {   int nProcId, nProcNo;   int nNameLen;   char szMachineName[MPI_MAX_PROCESSOR_NAME];   MPI_Init (&argc, &argv); // Start up MPI   MPI_Comm_size (MPI_COMM_WORLD,&nProcNo); // Find out number of processes   MPI_Comm_rank (MPI_COMM_WORLD, &nProcId); // Find out process rank   MPI_Get_processor_name (szMachineName, &nNameLen); // Get machine name   printf ("Hello World from process %d on %s\r\n", nProcId, szMachineName);   if (nProcId == 0)      printf ("Number of Processes: %d\r\n", nProcNo);   MPI_Finalize (); // Shut down MPI   return 0;}我的問題是MPI_Comm_Rank該過程的所有副本都返回0。當我在外殼上運行此命令時：mpirun -np 4  helloWorld它產生以下輸出：Hello World from process 0 on debianNumber of Processes: 1Hello World from process 0 on debianNumber of Processes: 1Hello World from process 0 on debianNumber of Processes: 1Hello World from process 0 on debianNumber of Processes: 1為什么進程數仍為1？