Question

I am using mpiexec to run a couple of hello world executables. They each run, but the number of processes is always 1 where it looks like there should be 4 processes. Does someone understand why? Also I m not sure why stty is giving me an invalid argument. Thanks!

Here is the output:

   /bin/stty: standard input: invalid argument
   Hello world from process 0 of 1
   Hello world from process 0 of 1
   Hello world from process 0 of 1
   Hello world from process 0 of 1

Here is the c file:

#include <stdio.h>
#include <mpi.h>

int main(int argc, char *argv[])
{
  int rank, size;
  MPI_Init (&argc, &argv);
  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
  MPI_Comm_size(MPI_COMM_WORLD, &size);
  printf("Hello world from process %d of %d
", rank, size);
  fflush(stdout);
  MPI_Finalize();
  return 0;
}

Here is the submission script:

#!/bin/bash

#PBS -N helloWorld
#PBS -l select=4:ncpus=2
#PBS -j oe
#PBS -o output
#PBS -l walltime=3:00
cd $PBS_O_WORKDIR


mpiexec ./helloWorld

Answer 1

Steven:

The above should work; it looks like something along the line (PBS <-> MPI library <-> mpiexec) is misconfigured.

The first, most obvious guess -- is the mpiexec the same mpi launching program that corresponds to the library you compiled with? If you do a which mpiexec in your script, do you get something that corresponds to the which mpicc when you compile the program? Do you have to do anything like a "module load [mpi package]" before you compile?

Similarly, is your mpiexec PBS-aware? If not, you might have to specify a hostfile (${PBS_NODEFILE}) somehow, and the number of processors.

What mpi are you using, and what system are you running on -- is it a publically available system with documentation we can look at?

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