root/ompi/mca/topo/base/topo_base_cart_shift.c

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DEFINITIONS

This source file includes following definitions.
  1. mca_topo_base_cart_shift

   1 /*
   2  * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
   3  *                         University Research and Technology
   4  *                         Corporation.  All rights reserved.
   5  * Copyright (c) 2004-2013 The University of Tennessee and The University
   6  *                         of Tennessee Research Foundation.  All rights
   7  *                         reserved.
   8  * Copyright (c) 2004-2005 High Performance Computing Center Stuttgart,
   9  *                         University of Stuttgart.  All rights reserved.
  10  * Copyright (c) 2004-2005 The Regents of the University of California.
  11  *                         All rights reserved.
  12  * Copyright (c) 2008      Cisco Systems, Inc.  All rights reserved.
  13  * Copyright (c) 2012-2013 Inria.  All rights reserved.
  14  * $COPYRIGHT$
  15  *
  16  * Additional copyrights may follow
  17  *
  18  * $HEADER$
  19  */
  20 
  21 #include "ompi_config.h"
  22 #include "ompi/mca/topo/base/base.h"
  23 #include "ompi/communicator/communicator.h"
  24 
  25 /*
  26  * function - Returns the shifted source and destination ranks, given a
  27  *            shift direction and amount
  28  *
  29  * @param comm communicator with cartesian structure (handle)
  30  * @param direction coordinate directionension of shift (integer)
  31  * @param disp displacement (> 0: upwards shift, < 0: downwards shift) (integer)
  32  * @param rank_source rank of source process (integer)
  33  * @param rank_dest rank of destination process (integer)
  34  *
  35  * The 'direction' argument is in the range '[0,n-1]' for an n-directionensional
  36  * Cartesian mesh.
  37  *
  38  * @retval MPI_SUCCESS
  39  */
  40 int mca_topo_base_cart_shift(ompi_communicator_t* comm,
  41                              int direction,
  42                              int disp,
  43                              int *rank_source,
  44                              int *rank_dest)
  45 {
  46     int factor, thisdirection = 0, thisperiod = 0, ord;
  47     int srcord, destord, i, *d, *q;
  48 
  49     /*
  50      * Handle the trivial case.
  51      */
  52     ord = ompi_comm_rank(comm);
  53 
  54     if (disp == 0) {
  55         *rank_dest = *rank_source = ord;
  56         return MPI_SUCCESS;
  57     }
  58     /*
  59      * Compute the rank factor and ordinate.
  60      */
  61     factor = ompi_comm_size(comm);
  62     d = comm->c_topo->mtc.cart->dims;
  63     q = comm->c_topo->mtc.cart->periods;
  64     for (i = 0; (i < comm->c_topo->mtc.cart->ndims) && (i <= direction); ++i, ++d, ++q) {
  65         thisdirection = *d;
  66         thisperiod = *q;
  67 
  68         ord %= factor;
  69         factor /= thisdirection;
  70     }
  71 
  72     ord /= factor;
  73     /*
  74      * Check the displacement value and compute the new ranks.
  75      */
  76     *rank_source = *rank_dest = MPI_UNDEFINED;
  77 
  78     srcord = ord - disp;
  79     destord = ord + disp;
  80     if ( ((destord < 0) || (destord >= thisdirection)) && (!thisperiod) ) {
  81         *rank_dest = MPI_PROC_NULL;
  82     } else {
  83         destord %= thisdirection;
  84         if (destord < 0) destord += thisdirection;
  85         *rank_dest = ompi_comm_rank(comm);
  86         *rank_dest += ((destord - ord) * factor);
  87     }
  88     if ( ((srcord < 0) || (srcord >= thisdirection)) && (!thisperiod) ) {
  89         *rank_source = MPI_PROC_NULL;
  90     } else {
  91         srcord %= thisdirection;
  92         if (srcord < 0) srcord += thisdirection;
  93         *rank_source= ompi_comm_rank(comm);
  94         *rank_source += ((srcord - ord) * factor);
  95     }
  96 
  97     return MPI_SUCCESS;
  98 }

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