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/*
* Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
* University Research and Technology
* Corporation. All rights reserved.
* Copyright (c) 2004-2013 The University of Tennessee and The University
* of Tennessee Research Foundation. 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 (c) 2008 Cisco Systems, Inc. All rights reserved.
* Copyright (c) 2012-2013 Inria. All rights reserved.
* $COPYRIGHT$
*
* Additional copyrights may follow
*
* $HEADER$
*/
#include "ompi_config.h"
#include "ompi/mca/topo/base/base.h"
#include "ompi/communicator/communicator.h"
/*
* function - Returns the shifted source and destination ranks, given a
* shift direction and amount
*
* @param comm communicator with cartesian structure (handle)
* @param direction coordinate directionension of shift (integer)
* @param disp displacement (> 0: upwards shift, < 0: downwards shift) (integer)
* @param rank_source rank of source process (integer)
* @param rank_dest rank of destination process (integer)
*
* The 'direction' argument is in the range '[0,n-1]' for an n-directionensional
* Cartesian mesh.
*
* @retval MPI_SUCCESS
*/
int mca_topo_base_cart_shift(ompi_communicator_t* comm,
int direction,
int disp,
int *rank_source,
int *rank_dest)
{
int factor, thisdirection = 0, thisperiod = 0, ord;
int srcord, destord, i, *d, *q;
/*
* Handle the trivial case.
*/
ord = ompi_comm_rank(comm);
if (disp == 0) {
*rank_dest = *rank_source = ord;
return MPI_SUCCESS;
}
/*
* Compute the rank factor and ordinate.
*/
factor = ompi_comm_size(comm);
d = comm->c_topo->mtc.cart->dims;
q = comm->c_topo->mtc.cart->periods;
for (i = 0; (i < comm->c_topo->mtc.cart->ndims) && (i <= direction); ++i, ++d, ++q) {
thisdirection = *d;
thisperiod = *q;
ord %= factor;
factor /= thisdirection;
}
ord /= factor;
/*
* Check the displacement value and compute the new ranks.
*/
*rank_source = *rank_dest = MPI_UNDEFINED;
srcord = ord - disp;
destord = ord + disp;
if ( ((destord < 0) || (destord >= thisdirection)) && (!thisperiod) ) {
*rank_dest = MPI_PROC_NULL;
} else {
destord %= thisdirection;
if (destord < 0) destord += thisdirection;
*rank_dest = ompi_comm_rank(comm);
*rank_dest += ((destord - ord) * factor);
}
if ( ((srcord < 0) || (srcord >= thisdirection)) && (!thisperiod) ) {
*rank_source = MPI_PROC_NULL;
} else {
srcord %= thisdirection;
if (srcord < 0) srcord += thisdirection;
*rank_source= ompi_comm_rank(comm);
*rank_source += ((srcord - ord) * factor);
}
return MPI_SUCCESS;
}
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