bsp_exptable.c

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/*
    BSPonMPI. This is an implementation of the BSPlib standard on top of MPI
    Copyright (C) 2006  Wijnand J. Suijlen
                                                                                
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.
                                                                                
    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.
                                                                                
    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
                                                                                
    You may contact me via electronic mail:
      wjsuijle@users.sourceforge.net
    or snail mail:
      W.J. Suijlen
      Kraaiheidelaan 10
      2803 VP Gouda
      The Netherlands
*/

#include "bsp_exptable.h"
#include "bsp_alloc.h"
#include "bsp_abort.h"
void
expandableTable_comm (const ExpandableTable * restrict send, 
                      ExpandableTable *restrict  recv, MPI_Comm communicator)
{
  int total_bytes_and_counts_to_send[2 * send->nprocs];
  int total_bytes_and_counts_to_recv[2 * send->nprocs];
  int recv_offset[send->nprocs], send_offset[send->nprocs];
  int recv_bytes[send->nprocs], send_bytes[send->nprocs];
  int max_slots_used, i;
  /* 
     index % 2 == 0 -> total used_slot_count in all tables
     index % 2 == 1 -> total count in all tables
  */
  for (i = 0; i < send->nprocs; i++)
    {
      total_bytes_and_counts_to_send[2 * i] = send->used_slot_count[i];
      total_bytes_and_counts_to_send[2 * i + 1] = send->count[i];
    }
  
    /* communicate this number */
  MPI_Alltoall (total_bytes_and_counts_to_send, 2, MPI_INT,
                total_bytes_and_counts_to_recv, 2, MPI_INT, communicator);

  for (i = 0; i < send->nprocs; i++)
    {
      recv->used_slot_count[i] = total_bytes_and_counts_to_recv[2 * i] ;
      recv->count[i] = total_bytes_and_counts_to_recv[2 * i + 1];
    }

  /* Expand recv table if necessary */
  max_slots_used = 0;
  /* calc maximal recv bytes */
  for (i = 0; i < send->nprocs; i++)
    max_slots_used = MAX (max_slots_used, recv->used_slot_count[i]);

  if (max_slots_used > recv->rows)      /* received data too big for current table */
    {
      /* I reallocate the memory */
      bsp_free (recv->data);
      recv->data =
        bsp_malloc (recv->nprocs * max_slots_used *2, recv->slot_size);
      recv->rows = max_slots_used * 2;
    }
  /* now the recv table can contain the receiving data in whole */

  /* initalize recv offsets */
  for (i = 0; i < recv->nprocs; i++)
    {
      recv_offset[i] = i * recv->rows * recv->slot_size;
      send_offset[i] = i * send->rows * send->slot_size;
      send_bytes[i] = send->used_slot_count[i] * send->slot_size;
      recv_bytes[i] = recv->used_slot_count[i] * recv->slot_size;
    }
  /* the next thing to do is to walk the send table and actually send the 
   * data */
  
  MPI_Alltoallv (send->data, send_bytes, send_offset, MPI_BYTE,
      recv->data, recv_bytes, recv_offset, MPI_BYTE, communicator);
}

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