BaseCode.c

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

#define ROOT 0
#define FIRST 0
#define LAST 1

int main(int argc, char* argv[]) {
    MPI_Init(&argc, &argv);
    
    MPI_Comm spawn, new_comm;
    MPI_Comm_get_parent(&spawn);
    if(spawn == MPI_COMM_NULL) {
	int num_c = atoi(argv[1]);
        MPI_Comm_spawn(argv[0], MPI_ARGV_NULL, num_c, MPI_INFO_NULL, ROOT, MPI_COMM_WORLD, &spawn, MPI_ERRCODES_IGNORE);
        MPI_Intercomm_merge(spawn, FIRST,  &new_comm);
    } else {
        MPI_Intercomm_merge(spawn, LAST, &new_comm);
	MPI_Barrier(MPI_COMM_WORLD);
    }
    MPI_Comm_disconnect(&spawn);
    MPI_Comm_disconnect(&new_comm);

    MPI_Finalize(); 
}