GLCS-CM5-TDXMP/manager-spawn.c

/* Code Example from http://mpi-forum.org/docs/mpi-2.0/mpi-20-html/node98.htm */
#include "mpi.h"
#include <stdio.h>

int main(int argc, char *argv[]) {
  int world_size, universe_size, *universe_sizep, flag;
  MPI_Comm everyone; /* intercommunicator */
  char worker_program[100];

  MPI_Init(&argc, &argv);
  MPI_Comm_size(MPI_COMM_WORLD, &world_size);

  if (world_size != 1)
    printf("Top heavy with management\n\n");

  MPI_Attr_get(MPI_COMM_WORLD, MPI_UNIVERSE_SIZE, &universe_sizep, &flag);
  if (!flag) {
    printf("This MPI does not support UNIVERSE_SIZE. \n How many processes "
           "total?");
    scanf("%d", &universe_size);
  } else {
    universe_size = *universe_sizep;
    printf("Universe size = %d \n", universe_size);
  }
  if (universe_size == 1)
    printf("No room to start workers SO I SET IT TO 5 \n");

  /*
   * Now spawn the workers. Note that there is a run-time determination
   * of what type of worker to spawn, and presumably this calculation must
   * be done at run time and cannot be calculated before starting
   * the program. If everything is known when the application is
   * first started, it is generally better to start them all at once
   * in a single MPI_COMM_WORLD.
   */
  universe_size = 5;
  /* choose_worker_program(worker_program); */
  MPI_Comm_spawn("./worker_program", MPI_ARGV_NULL, universe_size - 1,
                 MPI_INFO_NULL, 0, MPI_COMM_SELF, &everyone,
                 MPI_ERRCODES_IGNORE);
  /*
   * Parallel code here. The communicator "everyone" can be used
   * to communicate with the spawned processes, which have ranks 0,..
   * MPI_UNIVERSE_SIZE-1 in the remote group of the intercommunicator
   * "everyone".
   */

  MPI_Finalize();
  return 0;
}