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

#define NUM_SLAVES	4		/* create NUM_SLAVES processes	*/
#define SLAVE_PROG	"spawn_slave"	/* slave program name		*/


int main (int argc, char *argv[])
{
  MPI_Comm COMM_CHILD_PROCESSES;	/* inter-communicator		*/
  int	   ntasks_world,		/* # of tasks in MPI_COMM_WORLD	*/
	   ntasks_local,		/* COMM_CHILD_PROCESSES local	*/
	   ntasks_remote,		/* COMM_CHILD_PROCESSES remote	*/
	   mytid,			/* my task id			*/
	   namelen;			/* length of processor name	*/
  char	   processor_name[MPI_MAX_PROCESSOR_NAME];

  MPI_Init (&argc, &argv);
  MPI_Comm_rank (MPI_COMM_WORLD, &mytid);
  MPI_Comm_size (MPI_COMM_WORLD, &ntasks_world);
  /* check that only the master process is running in MPI_COMM_WORLD.   */
  if (ntasks_world > 1)
  {
    if (mytid == 0)
    {
      fprintf (stderr, "\n\nError: Too many processes (only one "
	       "process allowed).\n"
	       "Usage:\n"
	       "  mpiexec %s\n\n",
	       argv[0]);
    }
    MPI_Finalize ();
    exit (EXIT_SUCCESS);
  }
  MPI_Get_processor_name (processor_name, &namelen);
  printf ("\nParent process %d running on %s\n"
	  "  I create %d slave processes\n\n",
	  mytid,  processor_name, NUM_SLAVES);
  MPI_Comm_spawn (SLAVE_PROG, MPI_ARGV_NULL, NUM_SLAVES,
		  MPI_INFO_NULL, 0, MPI_COMM_WORLD,
		  &COMM_CHILD_PROCESSES, MPI_ERRCODES_IGNORE);
  MPI_Comm_size	(COMM_CHILD_PROCESSES, &ntasks_local);
  MPI_Comm_remote_size (COMM_CHILD_PROCESSES, &ntasks_remote);
  printf ("Parent process %d: "
	  "tasks in MPI_COMM_WORLD:                    %d\n"
	  "                  tasks in COMM_CHILD_PROCESSES local "
	  "group:  %d\n"
	  "                  tasks in COMM_CHILD_PROCESSES remote "
	  "group: %d\n\n",
	  mytid, ntasks_world, ntasks_local, ntasks_remote);
  MPI_Comm_free (&COMM_CHILD_PROCESSES);
  MPI_Finalize ();
  return EXIT_SUCCESS;
}