src/smpi/colls/alltoall-ompi-pairwise.c

   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) 2004-2006 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  * $COPYRIGHT$
  13  *
  14  * Additional copyrights may follow
  15  *
  16  * $HEADER$
  17  */
  18
  19 #include "colls_private.h"
  20
  21 int smpi_coll_tuned_alltoall_ompi_pairwise(void *sbuf, int scount,
  22                                             MPI_Datatype sdtype,
  23                                             void* rbuf, int rcount,
  24                                             MPI_Datatype rdtype,
  25                                             MPI_Comm comm)
  26 {
  27     int rank, size, step;
  28     int sendto, recvfrom;
  29     void * tmpsend, *tmprecv;
  30     MPI_Aint lb, sext, rext;
  31
  32     size = smpi_comm_size(comm);
  33     rank = smpi_comm_rank(comm);
  34
  35     XBT_VERB(
  36                  "coll:tuned:alltoall_ompi_pairwise rank %d", rank);
  37
  38     smpi_datatype_extent (sdtype, &lb, &sext);
  39     smpi_datatype_extent (rdtype, &lb, &rext);
  40
  41
  42     /* Perform pairwise exchange - starting from 1 so the local copy is last */
  43     for (step = 1; step < size + 1; step++) {
  44
  45         /* Determine sender and receiver for this step. */
  46         sendto  = (rank + step) % size;
  47         recvfrom = (rank + size - step) % size;
  48
  49         /* Determine sending and receiving locations */
  50         tmpsend = (char*)sbuf + sendto * sext * scount;
  51         tmprecv = (char*)rbuf + recvfrom * rext * rcount;
  52
  53         /* send and receive */
  54         smpi_mpi_sendrecv( tmpsend, scount, sdtype, sendto,
  55                                         COLL_TAG_ALLTOALL,
  56                                         tmprecv, rcount, rdtype, recvfrom,
  57                                         COLL_TAG_ALLTOALL,
  58                                         comm, MPI_STATUS_IGNORE);
  59     }
  60
  61     return MPI_SUCCESS;
  62 }