/* -*- Mode: C; c-basic-offset:4 ; -*- */

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

int main(int argc, char* argv[])
{
    int ID, NumberProcesses;
    char ProcessorName[MPI_MAX_PROCESSOR_NAME];
    int ProcessorNameLength;
    int *UniverseSize, Flag;
    MPI_Comm InterComm, IntraComm;

    MPI_Init(&argc, &argv);

    if (argc != 2) {
        fprintf(stderr, "usage: %s [./Spawn | ./SpawnChild]\n", argv[0]);
        fflush(stderr);
        MPI_Abort(MPI_COMM_WORLD, 1);
    }

    MPI_Comm_get_attr(MPI_COMM_WORLD, MPI_UNIVERSE_SIZE, &UniverseSize, &Flag);
    MPI_Comm_size(MPI_COMM_WORLD, &NumberProcesses);
    MPI_Comm_rank(MPI_COMM_WORLD, &ID);

    if (Flag && (*UniverseSize > 1) && (NumberProcesses == 1))
      {
	MPI_Comm_get_parent(&InterComm);
	if (InterComm == MPI_COMM_NULL)
	  {
	    int Error;
	    int* ErrorCodes;

	    ErrorCodes = (int*) calloc(*UniverseSize - 1, sizeof(int));
	    printf("Spawn %d children\n", *UniverseSize - 1);
	    Error = MPI_Comm_spawn(argv[1], MPI_ARGV_NULL, *UniverseSize - 1,
				   MPI_INFO_NULL, 0, MPI_COMM_WORLD,
				   &InterComm, ErrorCodes);
	    if (Error)
	      printf("Can't spawn child processes\n");
	    MPI_Intercomm_merge(InterComm, 0, &IntraComm);
	    free(ErrorCodes);
	  }
	else
	  MPI_Intercomm_merge(InterComm, 1, &IntraComm);
	MPI_Comm_size(IntraComm, &NumberProcesses);
	MPI_Comm_rank(IntraComm, &ID);
      }
    MPI_Get_processor_name(ProcessorName, &ProcessorNameLength);
    printf("Start process %d of %d on %s in universe of %d\n",
	   ID, NumberProcesses, ProcessorName, *UniverseSize);

    MPI_Finalize();
    return 0;
}