xt_exchanger.c

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/*
 * Keywords:
 * Maintainer: Jörg Behrens <behrens@dkrz.de>
 *             Moritz Hanke <hanke@dkrz.de>
 *             Thomas Jahns <jahns@dkrz.de>
 * URL: https://doc.redmine.dkrz.de/yaxt/html/
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are  permitted provided that the following conditions are
 * met:
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 *
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 * may be used to endorse or promote products derived from this software
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 */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <string.h>
#include <stdlib.h>

#include "xt_exchanger.h"
#include "xt_exchanger_irecv_isend.h"
#include "xt_exchanger_mix_isend_irecv.h"
#include "xt_exchanger_irecv_isend_packed.h"

Xt_exchanger (*xt_exchanger_default_constructor)
  (int nsend, int nrecv, struct Xt_redist_msg * send_msgs,
   struct Xt_redist_msg * recv_msgs, MPI_Comm comm, int tag_offset) =
    xt_exchanger_mix_isend_irecv_new;
    // xt_exchanger_irecv_isend_new;

Xt_exchanger
xt_exchanger_copy(Xt_exchanger exchanger, MPI_Comm new_comm, int new_tag_offset)
{
  return exchanger->vtable->copy(exchanger, new_comm, new_tag_offset);
}

void xt_exchanger_delete(Xt_exchanger exchanger) {

  exchanger->vtable->delete(exchanger);
}

void xt_exchanger_s_exchange(Xt_exchanger exchanger, const void *src_data, void *dst_data) {

  exchanger->vtable->s_exchange(exchanger, src_data, dst_data);
}

static int compare_exchange_messages (const void * msg_a, const void * msg_b)
{
  int rank_a = *(const int *)msg_a;
  int rank_b = *(const int *)msg_b;
  return ( rank_a - rank_b );
}

void xt_exchanger_internal_optimize(size_t n, void * msgs, size_t msg_type_size,
                                    MPI_Comm comm) {

  int comm_rank, comm_size;
  MPI_Comm_rank(comm, &comm_rank);
  MPI_Comm_size(comm, &comm_size);
  /* In order to avoid congestion of messages, the order of send and receive
   * messages is changed. This is done by sorting the messages according to the
   * rank of the respective message partner. Before the sorting to ranks that
   * are smaller or equal to the local rank the size of the communicator is
   * added.
   * example: process 5 is supposed to communicate with processes: 9, 5, 2, 6, 1
   * 1. add comm_size(10): 9, 15, 12, 6, 11
   * 2. sort: 6, 9, 11, 12, 15 -> final order: 6, 9, 1, 2, 5
   */
  unsigned char *msgs_ = (unsigned char *)msgs;
  /* apply offset for ranks <= comm_rank */
  for (size_t i = 0; i < n; ++i) {
    int *p = (int *)(void *)(msgs_ + i * msg_type_size),
      r = *p;
    if (r <= comm_rank) *p = r + comm_size;
  }
  qsort(msgs, n, msg_type_size, compare_exchange_messages);
  /* undo offset */
  for (size_t i = 0; i < n; ++i) {
    int *p = (int *)(void *)(msgs_ + i * msg_type_size),
      r = *p;
    if (r >= comm_size) *p = r - comm_size;
  }
}


int
xt_exchanger_get_msg_ranks(Xt_exchanger exchanger,
                           enum xt_msg_direction direction,
                           int **ranks)
{
  return exchanger->vtable->get_msg_ranks(exchanger, direction, ranks);
}

MPI_Datatype
xt_exchanger_get_MPI_Datatype(Xt_exchanger exchanger,
                              int rank, enum xt_msg_direction direction) {
  return exchanger->vtable->get_MPI_Datatype(exchanger, rank, direction);
}

/*
 * Local Variables:
 * c-basic-offset: 2
 * coding: utf-8
 * indent-tabs-mode: nil
 * show-trailing-whitespace: t
 * require-trailing-newline: t
 * End:
 */