/*
 * Copyright (c) 2004-2005 The Trustees of Indiana University.
 *                         All rights reserved.
 * Copyright (c) 2004-2005 The Trustees of the University of Tennessee.
 *                         All rights reserved.
 * Copyright (c) 2004-2005 High Performance Computing Center Stuttgart, 
 *                         University of Stuttgart.  All rights reserved.
 * Copyright (c) 2004-2005 The Regents of the University of California.
 *                         All rights reserved.
 * $COPYRIGHT$
 * 
 * Additional copyrights may follow
 * 
 * $HEADER$
 */
#include "ompi_config.h"
#include <stdio.h>

#include "mpi/c/bindings.h"
#include "ompi/communicator/communicator.h"
#include "ompi/errhandler/errhandler.h"
#include "ompi/group/group.h"
#include "ompi/proc/proc.h"

#if OMPI_HAVE_WEAK_SYMBOLS && OMPI_PROFILING_DEFINES
#pragma weak MPI_Group_difference = PMPI_Group_difference
#endif

#if OMPI_PROFILING_DEFINES
#include "mpi/c/profile/defines.h"
#endif

static const char FUNC_NAME[] = "MPI_Group_difference";


int MPI_Group_difference(MPI_Group group1, MPI_Group group2,
                         MPI_Group *new_group) {

    /* local varibles */
    int new_group_size, proc1, proc2, found_in_group2, cnt;
    int my_group_rank;
    ompi_group_t *group1_pointer, *group2_pointer, *new_group_pointer;
    ompi_proc_t *proc1_pointer, *proc2_pointer, *my_proc_pointer = NULL;

    /* error checking */
    if( MPI_PARAM_CHECK ) {
        OMPI_ERR_INIT_FINALIZE(FUNC_NAME);

        if( (MPI_GROUP_NULL == group1) || (MPI_GROUP_NULL == group2) ||
                (NULL == group1) || (NULL == group2) ) {
            return OMPI_ERRHANDLER_INVOKE(MPI_COMM_WORLD, MPI_ERR_GROUP,
                                          FUNC_NAME);
        }
    }


    group1_pointer=(ompi_group_t *)group1;
    group2_pointer=(ompi_group_t *)group2;

    /*
     * form union
     */

    /* get new group size */
    new_group_size=0;

    /* loop over group1 members */
    for( proc1=0; proc1 < group1_pointer->grp_proc_count; proc1++ ) {
        proc1_pointer=group1_pointer->grp_proc_pointers[proc1];
        /* check to see if this proc is in group2 */
        found_in_group2=0;
        for( proc2=0 ; proc2 < group2_pointer->grp_proc_count ; proc2++ ) {
            proc2_pointer=group2_pointer->grp_proc_pointers[proc2];
            if( proc1_pointer == proc2_pointer ) {
                found_in_group2=true;
                break;
            }
        }  /* end proc1 loop */
        if(found_in_group2)
            continue;
        new_group_size++;
    }  /* end proc loop */

    if ( 0 == new_group_size ) {
	*new_group = MPI_GROUP_EMPTY;
	OBJ_RETAIN(MPI_GROUP_EMPTY);
	return MPI_SUCCESS;
    }

    /* allocate a new ompi_group_t structure */
    new_group_pointer=ompi_group_allocate(new_group_size);
    if( NULL == new_group_pointer ) {
        return OMPI_ERRHANDLER_INVOKE(MPI_COMM_WORLD, MPI_ERR_GROUP,
                "MPI_Group_difference - II");
    }

    /* fill in group list */
    cnt=0;
    /* loop over group1 members */
    for( proc1=0; proc1 < group1_pointer->grp_proc_count; proc1++ ) {
        proc1_pointer=group1_pointer->grp_proc_pointers[proc1];
        /* check to see if this proc is in group2 */
        found_in_group2=0;
        for( proc2=0 ; proc2 < group2_pointer->grp_proc_count ; proc2++ ) {
            proc2_pointer=group2_pointer->grp_proc_pointers[proc2];
            if( proc1_pointer == proc2_pointer ) {
                found_in_group2=true;
                break;
            }
        }  /* end proc1 loop */
        if(found_in_group2)
            continue;

        new_group_pointer->grp_proc_pointers[cnt] =
            group1_pointer->grp_proc_pointers[proc1];

        cnt++;
    }  /* end proc loop */

    /* increment proc reference counters */
    ompi_group_increment_proc_count(new_group_pointer);

    /* find my rank */
    my_group_rank=group1_pointer->grp_my_rank;
    if ( MPI_UNDEFINED != my_group_rank ) {
	my_proc_pointer=group1_pointer->grp_proc_pointers[my_group_rank];
    }
    else {
	my_group_rank=group2_pointer->grp_my_rank;
	if ( MPI_UNDEFINED != my_group_rank ) {
	    my_proc_pointer=group2_pointer->grp_proc_pointers[my_group_rank];
	}
    }

    if ( MPI_UNDEFINED == my_group_rank ) {
	new_group_pointer->grp_my_rank = MPI_UNDEFINED;
    }
    else {
	ompi_set_group_rank(new_group_pointer,my_proc_pointer);
    }

    *new_group = (MPI_Group)new_group_pointer;

    return MPI_SUCCESS;
}