#include <mpi.h>

int main(int argc, char **argv){
  char myport[MPI_MAX_PORT_NAME];
  MPI_Comm intercomm,intracomm;
  int i,j,s;

  MPI_Init(&argc,&argv);
  printf("%s: MPI_Open_port..\n",argv[0]);
  MPI_Open_port(MPI_INFO_NULL, myport);
  printf("%s: mpiport=%s\n",argv[0], myport);
  printf("%s: MPI_Comm_Accept..\n",argv[0]);
  MPI_Comm_accept(myport, MPI_INFO_NULL, 0, MPI_COMM_WORLD, &intercomm);
  MPI_Comm_size(intercomm,&s);
  printf("%s: Size of intercommunicator: %i\n",argv[0],s);
//  printf("%s: MPI_Barrier..\n",argv[0]);
//  MPI_Barrier(intercomm);
  i=8;
  printf("%s: intercomm, MPI_Allreduce..\n",argv[0]);
  MPI_Allreduce(&i,&j,1,MPI_INT,MPI_SUM,intercomm);
  printf("%s: intercomm, my_value=%i SUM=%i\n",argv[0],i,j);
  MPI_Intercomm_merge(intercomm,0,&intracomm);
  printf("%s: intracomm, MPI_Allreduce..\n",argv[0]);
  MPI_Allreduce(&i,&j,1,MPI_INT,MPI_SUM,intracomm);
  printf("%s: intracomm, my_value=%i SUM=%i\n",argv[0],i,j);
  printf("Done\n");
  printf("%s: Done\n",argv[0]);
  MPI_Finalize();
}