/* -*- Mode: C; c-basic-offset:4 ; -*- */
/*
 *  (C) 2001 by Argonne National Laboratory.
 *      See COPYRIGHT in top-level directory.
 */
#include "mpi.h"
#include <stdio.h>
#define BAD_ANSWER 100000

int assoc ( int *, int *, int *, MPI_Datatype * );

/*
    The operation is inoutvec[i] = invec[i] op inoutvec[i] 
    (see 4.9.4).  The order is important.

    Note that the computation is in process rank (in the communicator)
    order, independant of the root.
 */
int assoc(int *invec, int *inoutvec, int *len, MPI_Datatype *dtype)
{
  int i;
  for ( i=0; i<*len; i++ )  {
    if (inoutvec[i] <= invec[i] ) {
      int rank;
      MPI_Comm_rank( MPI_COMM_WORLD, &rank );
      fprintf( stderr, "[%d] inout[0] = %d, in[0] = %d\n", 
	       rank, inoutvec[0], invec[0] );
      inoutvec[i] = BAD_ANSWER;
      }
    else 
      inoutvec[i] = invec[i];
  }
  return (1);
}

int main( int argc, char **argv )
{
    int              rank, size;
    int              data;
    int              errors=0;
    int              result = -100;
    MPI_Op           op;

    MPI_Init( &argc, &argv );
    MPI_Comm_rank( MPI_COMM_WORLD, &rank );
    MPI_Comm_size( MPI_COMM_WORLD, &size );

    data = rank;

    MPI_Op_create( (MPI_User_function*)assoc, 0, &op );
    MPI_Reduce ( &data, &result, 1, MPI_INT, op, size-1, MPI_COMM_WORLD );
    MPI_Bcast  ( &result, 1, MPI_INT, size-1, MPI_COMM_WORLD );
    MPI_Op_free( &op );
    if (result == BAD_ANSWER) errors++;

    if (errors)
      printf( "[%d] done with ERRORS(%d)!\n", rank, errors );
    else {
	if (rank == 0) 
	    printf(" No Errors\n");
    }

    MPI_Finalize();

    return errors;
}
