#include <stdio.h>
#include <mpi.h>
#include <string.h>

#define buf_size 128

int
main (int argc, char **argv)
{
  int nprocs = -1;
  int rank = -1;
  char processor_name[128];
  int namelen = 128;
  int buf0[buf_size];
  int buf1[buf_size];
  MPI_Status status;
  MPI_Request req[2];

  /* init */
  MPI_Init (&argc, &argv);
  MPI_Comm_size (MPI_COMM_WORLD, &nprocs);
  MPI_Comm_rank (MPI_COMM_WORLD, &rank);
  MPI_Get_processor_name (processor_name, &namelen);
  printf ("(%d) is alive on %s\n", rank, processor_name);
  fflush (stdout);

  if (nprocs < 2)
    {
      printf ("not enough tasks\n");
    }
  else if (rank == 0)
    {
      memset (buf0, 0, buf_size);
      
      MPI_Isend (buf1, buf_size, MPI_INT, 2, 0, MPI_COMM_WORLD, &req[0]);
      MPI_Wait (&req[0], &status);

      MPI_Irecv (buf0, buf_size, MPI_INT, 
		 1, 0, MPI_COMM_WORLD, &req[1]);
      MPI_Wait (&req[1], &status);

    }
  else if (rank == 1)
    {
      memset (buf1, 1, buf_size);
      
      MPI_Isend (buf1, buf_size, MPI_INT, 0, 0, MPI_COMM_WORLD, &req[0]);
      MPI_Wait (&req[0], &status);
      MPI_Isend (buf1, buf_size, MPI_INT, 2, 0, MPI_COMM_WORLD, &req[1]);
      MPI_Wait (&req[1], &status);
    }

  else if (rank == 2)
    {
      memset (buf1, 1, buf_size);
      
      MPI_Irecv (buf0, buf_size, MPI_INT, 
		 MPI_ANY_SOURCE, 0, MPI_COMM_WORLD, &req[0]);
      MPI_Wait (&req[0], &status);

      MPI_Irecv (buf0, buf_size, MPI_INT, 
		 1, 0, MPI_COMM_WORLD, &req[1]);
      MPI_Wait (&req[1], &status);

    }


  //MPI_Barrier (MPI_COMM_WORLD);

  MPI_Finalize ();
  printf ("(%d) Finished normally\n", rank);
}

/* EOF */
