Artifact b88fed3ba842a6b3e5feb6380a29d93f6df0914da00d811e1dcb34e6debdaf68:

• Executable file r36/cslbase/cslmpi.c — part of check-in [f2fda60abd] at 2011-09-02 18:13:33 on branch master — Some historical releases purely for archival purposes

  git-svn-id: https://svn.code.sf.net/p/reduce-algebra/code/trunk/historical@1375 2bfe0521-f11c-4a00-b80e-6202646ff360 (user: arthurcnorman@users.sourceforge.net, size: 24377) [annotate] [blame] [check-ins using] [more...]

/*  cslmpi.c                                                        */

/*
 * Interfaces for mpi from CSL. The bulk of this code was written by
 * M O Seymour (199/98) who has released it for inclusion as part of
 * this Lisp system.
 */

/* Signature: 6962d5a4 28-Jan-1999 */

#include <stdarg.h>
#include <string.h>
#include <ctype.h>

#include "machine.h"
#include "tags.h"
#include "cslerror.h"
#include "externs.h"
#include "arith.h"
#include "entries.h"
#ifdef TIMEOUT
#include "timeout.h"
#endif


#ifdef USE_MPI

#include "read.h"

#include "mpipack.c"

#define check_fix(v) if (!is_fixnum(v)) return aerror1(fun_name, v)
#define get_arg(v) v = va_arg(a,Lisp_Object)
#define get_fix_arg(v) get_arg(v); check_fix(v); v=int_of_fixnum(v)  


/************************ Environmental functions *******************/

/* Returns process rank 
 * (mpi_comm_rank comm)
 */
/* For now, I assume that comm will fit into a fixnum.
 * This appears to be the case with MPICH (values in the hundreds),
 * but assumptions like this should not be made.
 */ 
static Lisp_Object Lmpi_comm_rank(Lisp_Object nil, Lisp_Object comm)
{
  int rank;
  static char fun_name[] = "mpi_comm_rank";
  CSL_IGNORE(nil);
  check_fix(comm);
  MPI_Comm_rank(int_of_fixnum(comm),&rank);
  return onevalue(fixnum_of_int(rank));
}

/* returns size of communicator
 * (mpi_comm_size comm)
 */
/* Same assumption about comm. */
static Lisp_Object Lmpi_comm_size(Lisp_Object nil, Lisp_Object comm)
{
  int size;
  static char fun_name[] = "mpi_comm_size";
  CSL_IGNORE(nil);
  check_fix(comm);
  MPI_Comm_size(int_of_fixnum(comm),&size);
  return onevalue(fixnum_of_int(size));
}

/********************** Blocking point-to-point functions *************/

/* Standard blocking send
 * (mpi_send message dest tag comm) 
 * returns nil.
 */
/*  Same assumption about comm. */
static Lisp_Object MS_CDECL Lmpi_send(Lisp_Object nil, int nargs, ...)
{
  static char fun_name[] = "mpi_send";

  Lisp_Object message;
  int dest,tag,comm;
  va_list a;
  argcheck(nargs,4,fun_name);
  va_start(a,nargs);
  get_arg(message); 
  get_fix_arg(dest); get_fix_arg(tag); get_fix_arg(comm);

  pack_object(message);
  MPI_Send(mpi_pack_buffer, mpi_pack_position, MPI_PACKED, 
	   dest, tag, comm);
  free(mpi_pack_buffer);
  return onevalue(nil);
}

/* Standard blocking receive 
 * (mpi_recv source tag comm)
 * returns (message (source tag error)).
 */
static Lisp_Object MS_CDECL Lmpi_recv(Lisp_Object nil, int nargs, ...) 
{
  static char fun_name[] = "mpi_recv";

  MPI_Status status;
  int source,tag,comm;
  Lisp_Object Lstatus;
  va_list a;

  CSL_IGNORE(nil);
  argcheck(nargs,3,fun_name);
  va_start(a,nargs);
  get_fix_arg(source); get_fix_arg(tag); get_fix_arg(comm);

  MPI_Probe(source, tag, comm, &status);
  MPI_Get_count(&status, MPI_PACKED, &mpi_pack_size);
  mpi_pack_buffer = (char*)malloc(mpi_pack_size);

  MPI_Recv(mpi_pack_buffer, mpi_pack_size, MPI_PACKED, 
	   source, tag, comm, &status);
  
  /* The only relevant status things are the 3 public fields, so I'll
   * stick them in a list and return them as the 2nd value
   */
  push(unpack_object());
  free(mpi_pack_buffer);
  Lstatus = list3(fixnum_of_int(status.MPI_SOURCE), 
		  fixnum_of_int(status.MPI_TAG),
		  fixnum_of_int(status.MPI_ERROR));

  return onevalue(list2(my_pop(),Lstatus)); 
}

/* Standard blocking simultaneous send and receive
 * (mpi_sendrecv send_message dest send_tag source recv_tag comm)
 * returns (recv_message (source recv_tag error))
 */
/* THERE IS A LIMIT OF 1024 BYTES FOR THE RECEIVE BUFFER (sorry.)
 * THIS WILL BE REMOVED ASAP.
 */
static Lisp_Object MS_CDECL Lmpi_sendrecv(Lisp_Object nil, int nargs, ...)
{
  static char fun_name[] = "mpi_sendrecv";

  MPI_Status status;
  Lisp_Object Lstatus;
  Lisp_Object s_mess; 
  int s_tag, r_tag, dest, source, comm;
  char r_buffer[1024];

  va_list a;
  CSL_IGNORE(nil);
  argcheck(nargs,6,fun_name);
  va_start(a,nargs);
  get_arg(s_mess); 
  get_fix_arg(dest); get_fix_arg(s_tag);
  get_fix_arg(source); get_fix_arg(r_tag); get_fix_arg(comm);

  pack_object(s_mess);
  MPI_Sendrecv(mpi_pack_buffer, mpi_pack_position, MPI_PACKED,
	       dest, s_tag,
	       r_buffer, 1024, MPI_PACKED,
	       source, r_tag, comm, &status);
  free(mpi_pack_buffer);
  mpi_pack_buffer = r_buffer;
  push(unpack_object());
  Lstatus = list3(fixnum_of_int(status.MPI_SOURCE), 
		  fixnum_of_int(status.MPI_TAG),
		  fixnum_of_int(status.MPI_ERROR));

  return onevalue(list2(my_pop(),Lstatus)); 
}

/************** Non-Blocking point-to-point functions ***********/

/* Standard non-blocking send post
 * (mpi_isend message dest tag comm)
 * returns request handle
 */
static Lisp_Object MS_CDECL Lmpi_isend(Lisp_Object nil, int nargs, ...)
{
  static char fun_name[] = "mpi_isend";

  Lisp_Object message, request;
  int dest, tag, comm;

  va_list a;
  CSL_IGNORE(nil);
  
  /* For now, we assume type MPI_Request to be 32 bits. */
  request = Lmkvect32(nil,fixnum_of_int(2));
  
  argcheck(nargs,4,fun_name);
  va_start(a,nargs);
  get_arg(message); 
  get_fix_arg(dest); get_fix_arg(tag); get_fix_arg(comm);
  
  pack_object(message);
  MPI_Isend(mpi_pack_buffer, mpi_pack_position, MPI_PACKED,
	    dest, tag, comm,  (MPI_Request*)&elt(request,0));
  elt(request,1) = (int)mpi_pack_buffer;
  return onevalue(request);
}

/* Standard non-blocking receive post
 * (mpi_irecv source tag comm)
 * returns request handle
 */
/* I actually cheat horribly by not posting the request at all (at least
 * not via MPI), but rather create my own "dummy" request structure.
 * Then, to complete the request, I MPI_(I)Probe for a matching message,
 * and receive it if it is there.
 * This is unsatisfactory since the operation is only non-blocking until the
 * first lump of the message arrives; for a long message, there may by
 * a lot of latency after this.
 */
struct dummy_request{
  int source;
  int tag;
  int comm;
};

static Lisp_Object MS_CDECL Lmpi_irecv(Lisp_Object nil, int nargs, ...)
{
  static char fun_name[] = "mpi_irecv";

  int source,tag,comm;
  Lisp_Object request;
  va_list a;
  char* buffer;
  CSL_IGNORE(nil);

  /* For now, we assume type MPI_Request to be 32 bits. */
  request = Lmkvect32(nil,fixnum_of_int(2));
  
  argcheck(nargs,3,fun_name);
  va_start(a,nargs);
  get_fix_arg(source); get_fix_arg(tag); get_fix_arg(comm);

  elt(request,1) = 0; /* There is no buffer yet */
  elt(request,0) = (int)malloc(sizeof(struct dummy_request));
  ((struct dummy_request*)elt(request,0))->source = source;
  ((struct dummy_request*)elt(request,0))->tag = tag;
  ((struct dummy_request*)elt(request,0))->comm = comm;
  
  return onevalue(request);
}

/* Wait to complete operation, and deallocate buffer.
 * (mpi_wait request)
 * for send, returns nil
 * for recv, returns (message (source tag error))
 */
static Lisp_Object Lmpi_wait(Lisp_Object nil, Lisp_Object request)
{
  MPI_Status status;
  Lisp_Object message, Lstatus;
  if ( !(is_vector(request) && type_of_header(vechdr(request)) == TYPE_VEC32 &&
	 length_of_header(vechdr(request)) == 3*CELL) ) 
    return aerror1("mpi_wait",request);
  if ( elt(request,1)){
    status.MPI_ERROR = MPI_UNDEFINED;
    mpi_pack_buffer = (void*)elt(request,1);
    MPI_Wait( (MPI_Request*)&elt(request,0), &status);
    if (status.MPI_ERROR == MPI_UNDEFINED){       /* i.e. send request */
      free(mpi_pack_buffer);
      return onevalue(nil);
    } 
    else {   /* old-style receive */
      push(unpack_object());
      free(mpi_pack_buffer);
      Lstatus = list3(fixnum_of_int(status.MPI_SOURCE), 
		      fixnum_of_int(status.MPI_TAG),
		      fixnum_of_int(status.MPI_ERROR));
      return onevalue(list2(my_pop(),Lstatus));
    } 
  }
  else{      /* new-style receive */
    int source = ((struct dummy_request*)elt(request,0))->source,
      tag = ((struct dummy_request*)elt(request,0))->tag,
      comm = ((struct dummy_request*)elt(request,0))->comm;
    MPI_Probe(source, tag, comm, &status);
    free((struct dummy_request*)elt(request,0));
    MPI_Get_count(&status, MPI_PACKED, &mpi_pack_size);
    mpi_pack_buffer = (char*)malloc(mpi_pack_size);

    MPI_Recv(mpi_pack_buffer, mpi_pack_size, MPI_PACKED, 
	     source, tag, comm, &status);
    
    /* The only relevant status things are the 3 public fields, so I'll
     * stick them in a list and return them as the 2nd value
     */
    push(unpack_object());
    free(mpi_pack_buffer);
    Lstatus = list3(fixnum_of_int(status.MPI_SOURCE), 
		    fixnum_of_int(status.MPI_TAG),
		    fixnum_of_int(status.MPI_ERROR));
    
    return onevalue(list2(my_pop(),Lstatus)); 
  }
}


/* Test for completion, deallocate buffer if so
 * (mpi_test request)
 * for send, returns flag
 * for recv, returns nil or (message (source tag error))
 */
static Lisp_Object Lmpi_test(Lisp_Object nil, Lisp_Object request)
{
  MPI_Status status;
  Lisp_Object message, Lstatus;
  int flag;
  if ( !(is_vector(request) && type_of_header(vechdr(request)) == TYPE_VEC32 &&
	 length_of_header(vechdr(request)) == 3*CELL) ) 
    return aerror1("mpi_wait",request);
  if (elt(request,1)){
    status.MPI_ERROR = MPI_UNDEFINED;
    mpi_pack_buffer = (void*)elt(request,1);
    MPI_Test( (MPI_Request*)&elt(request,0), &flag, &status);
    if (!flag) return onevalue(nil);
    if (status.MPI_ERROR == MPI_UNDEFINED){       /* send request */
      free(mpi_pack_buffer);
      return onevalue(Lispify_predicate(YES));
    } 
    else{   /* old-style receive */
      push(unpack_object());
      free(mpi_pack_buffer);
      Lstatus = list3(fixnum_of_int(status.MPI_SOURCE), 
		      fixnum_of_int(status.MPI_TAG),
		      fixnum_of_int(status.MPI_ERROR));
      
      return onevalue(list2(my_pop(),Lstatus));
    }
  }
  else {        /* new-style receive */
    int source = ((struct dummy_request*)elt(request,0))->source,
      tag = ((struct dummy_request*)elt(request,0))->tag,
      comm = ((struct dummy_request*)elt(request,0))->comm,   flag;
    MPI_Iprobe(source, tag, comm, &flag, &status);
    
    if (!flag) return onevalue(nil);
    
    free((struct dummy_request*)elt(request,0));
    MPI_Get_count(&status, MPI_PACKED, &mpi_pack_size);
    mpi_pack_buffer = (char*)malloc(mpi_pack_size);

    MPI_Recv(mpi_pack_buffer, mpi_pack_size, MPI_PACKED, 
	     source, tag, comm, &status);
    
    /* The only relevant status things are the 3 public fields, so I'll
     * stick them in a list and return them as the 2nd value
     */
    push(unpack_object());
    free(mpi_pack_buffer);
    Lstatus = list3(fixnum_of_int(status.MPI_SOURCE), 
		    fixnum_of_int(status.MPI_TAG),
		    fixnum_of_int(status.MPI_ERROR));
    
    return onevalue(list2(my_pop(),Lstatus)); 
  }
}

/************** Probe functions *******************/
/* Non-blocking probe
 * (mpi_iprobe source tag comm)
 * returns (flag (source tag error))
 */
static Lisp_Object MS_CDECL Lmpi_iprobe(Lisp_Object nil, int nargs, ...)
{
  static char fun_name[] = "impi_probe";

  MPI_Status status;
  int source, tag, comm, flag;
  Lisp_Object Lstatus;
  va_list a;

  CSL_IGNORE(nil);
  argcheck(nargs,3,fun_name);
  va_start(a,nargs);
  get_fix_arg(source); get_fix_arg(tag); get_fix_arg(comm);

  MPI_Iprobe(source, tag, comm, &flag, &status);
  Lstatus = list3(fixnum_of_int(status.MPI_SOURCE), 
		  fixnum_of_int(status.MPI_TAG),
		  fixnum_of_int(status.MPI_ERROR));
  return onevalue(list2(Lispify_predicate(flag), Lstatus));
}

/* Blocking probe
 * (mpi_probe source tag comm)
 * returns (source tag error)
 */
static Lisp_Object MS_CDECL Lmpi_probe(Lisp_Object nil, int nargs, ...)
{
  static char fun_name[] = "mpi_probe";

  MPI_Status status;
  int source, tag, comm;
  Lisp_Object Lstatus;
  va_list a;

  CSL_IGNORE(nil);
  argcheck(nargs,3,fun_name);
  va_start(a,nargs);
  get_fix_arg(source); get_fix_arg(tag); get_fix_arg(comm);

  MPI_Probe(source, tag, comm, &status);
  Lstatus = list3(fixnum_of_int(status.MPI_SOURCE), 
		  fixnum_of_int(status.MPI_TAG),
		  fixnum_of_int(status.MPI_ERROR));
  return onevalue(Lstatus);
}

/************** Collective Communications *********/

/* Barrier; blocks until all processes have called
 * (mpi_barrier comm)
 * returns nil
 */
static Lisp_Object Lmpi_barrier(Lisp_Object nil, Lisp_Object comm)
{
  int rank;
  static char fun_name[] = "mpi_barrier";
  check_fix(comm);
  MPI_Barrier(int_of_fixnum(comm));
  return onevalue(nil);
}

/* Broadcast; sends buffer of root to buffers of others.
 * (mpi_bcast message root comm)  [message ignored if not root]
 * returns message
 */
static Lisp_Object MS_CDECL Lmpi_bcast(Lisp_Object nil, int nargs, ...)
{
  static char fun_name[] = "mpi_bcast";

  Lisp_Object message;
  int root,comm,rank;
  va_list a;
  
  CSL_IGNORE(nil);
  argcheck(nargs,3,fun_name);
  va_start(a,nargs);
  get_arg(message); get_fix_arg(root); get_fix_arg(comm);
  
  MPI_Comm_rank(comm,&rank);
  if (rank == root){
    pack_object(message);
    MPI_Bcast(&mpi_pack_position, 1, MPI_LONG, root, comm);
    MPI_Bcast(mpi_pack_buffer, mpi_pack_position, MPI_PACKED, root, comm);
    free(mpi_pack_buffer);
  }
  else {
    MPI_Bcast(&mpi_pack_size, 1, MPI_LONG, root, comm);
    mpi_pack_buffer = (char*)malloc(mpi_pack_size);
    MPI_Bcast(mpi_pack_buffer, mpi_pack_size, MPI_PACKED, root, comm);
    message = unpack_object();
    free(mpi_pack_buffer);
  }
  return onevalue(message);
}

/* Gather: root receives messages from others.
 * (mpi_gather message root comm)
 * returns vector of messages if root, else nil.
 */
static Lisp_Object MS_CDECL Lmpi_gather(Lisp_Object nil, int nargs, ...)
{
  static char fun_name[] = "mpi_gather";

  Lisp_Object message;
  int root,comm,rank;
  va_list a;

  CSL_IGNORE(nil);
  argcheck(nargs,3,fun_name);
  va_start(a,nargs);
  get_arg(message); get_fix_arg(root); get_fix_arg(comm);
  
  MPI_Comm_rank(comm,&rank);
  pack_object(message);
  if (rank == root){
    int commsize, count;
    int *recvcounts, *displs;
    char *recvbuffer;

    MPI_Comm_size(comm,&commsize);
    recvcounts = (int*)calloc(commsize, sizeof(int));
    displs = (int*)calloc(commsize+1, sizeof(int));
    MPI_Gather(&mpi_pack_position, 1, MPI_LONG, 
	       recvcounts, 1, MPI_LONG, root, comm);

    displs[0] = 0;
    for (count = 0; count < commsize; ++count) 
      displs[count+1] = displs[count] + recvcounts[count];

    recvbuffer = (char*)malloc(displs[commsize]);

    MPI_Gatherv(mpi_pack_buffer, mpi_pack_position, MPI_PACKED, 
		recvbuffer, recvcounts, displs, MPI_PACKED, root, comm);
    free(mpi_pack_buffer);

    message = Lmkvect(nil, fixnum_of_int(commsize-1));
    for (count = 0; count < commsize; ++count){
      mpi_pack_buffer = recvbuffer + displs[count];
      mpi_pack_size = recvcounts[count];
      elt(message, count) = unpack_object();
    }
    free(recvbuffer); free(recvcounts); free(displs);
  }
  else {
    MPI_Gather(&mpi_pack_position, 1, MPI_LONG, 0, 0, MPI_LONG, root, comm);
    MPI_Gatherv(mpi_pack_buffer, mpi_pack_position, MPI_PACKED, 
		0,0,0,MPI_PACKED, root, comm);
    free(mpi_pack_buffer);
    message = nil;
  }
  return onevalue(message);
}

/* Scatter: inverse of gather.
 * (mpi_scatter vector_of_messages root comm)  [messages ignored if not root]
 * returns message
 */
static Lisp_Object MS_CDECL Lmpi_scatter(Lisp_Object nil, int nargs, ...)
{
  static char fun_name[] = "mpi_scatter";
  
  Lisp_Object messages, message;
  int root, comm, rank;
  va_list a;

  CSL_IGNORE(nil);
  argcheck(nargs,3,fun_name);
  va_start(a,nargs);
  get_arg(messages); get_fix_arg(root); get_fix_arg(comm);

  MPI_Comm_rank(comm,&rank);
  if (rank == root){
    int commsize, count, *sendcounts, *displs, recvcount;
    char* recvbuffer;

    MPI_Comm_size(comm,&commsize);
    sendcounts = (int*)calloc(commsize, sizeof(int));
    displs = (int*)calloc(commsize+1, sizeof(int));
    displs[0] = 0;

    /* Call private functions in mpi_packing for consecutive packs */
    check_buffer = scatter_check_buffer;
    mpi_pack_offset = 0;
    mpi_pack_position = 0;
    mpi_pack_size = 0;
    mpi_buffer_bottom = 0;
    mpi_real_size = 0;
    for (count = 0; count < commsize; ++count){
      pack_cell(elt(messages,count));
      sendcounts[count] = mpi_pack_position;
      mpi_pack_size -= mpi_pack_position;
      mpi_pack_offset += mpi_pack_position;
      mpi_pack_buffer += mpi_pack_position; 
      displs[count+1] = mpi_pack_offset;
      mpi_pack_position = 0;
    }
    check_buffer = default_check_buffer;
    MPI_Scatter(sendcounts, 1, MPI_LONG, &recvcount, 1, MPI_LONG, root, comm);
    recvbuffer = (char*)malloc(recvcount);
    MPI_Scatterv(mpi_buffer_bottom, sendcounts, displs, MPI_PACKED,
		 recvbuffer, recvcount, MPI_PACKED, root, comm);
    free(recvbuffer);
    free(sendcounts);
    free(displs);
    free(mpi_buffer_bottom);
    message = elt(messages, root);
  }
  else {
    MPI_Scatter(0,0,MPI_LONG,&mpi_pack_size,1,MPI_LONG,root,comm);
    mpi_pack_buffer = (char*)malloc(mpi_pack_size);
    MPI_Scatterv(0,0,0,MPI_PACKED,
		 mpi_pack_buffer,mpi_pack_size,MPI_PACKED,root,comm);
    message = unpack_object();
    free(mpi_pack_buffer);
  }
  return onevalue(message);
}


/* Allgather: just like gather, only everyone gets the result.
 * (mpi_allgather message comm)
 * returns vector of messages
 */
static Lisp_Object Lmpi_allgather(Lisp_Object nil, 
				  Lisp_Object message, 
				  Lisp_Object comm)
{
  static char fun_name[] = "mpi_gather";
  int commsize, buffersize, count;
  int *recvcounts, *displs;
  char *recvbuffer;

  check_fix(comm);
  comm = int_of_fixnum(comm);
  CSL_IGNORE(nil);
  
  pack_object(message);

  MPI_Comm_size(comm,&commsize);
  recvcounts = (int*)calloc(commsize, sizeof(int));
  displs = (int*)calloc(commsize+1, sizeof(int));
  MPI_Allgather(&mpi_pack_position, 1, MPI_LONG, recvcounts, 1, MPI_LONG, comm);
  
  displs[0] = 0;
  for (count = 0; count < commsize; ++count)
    displs[count+1] = displs[count] + recvcounts[count];

  recvbuffer = (char*)malloc(displs[commsize]);

  MPI_Allgatherv(mpi_pack_buffer, mpi_pack_position, MPI_PACKED,
		 recvbuffer, recvcounts, displs, MPI_PACKED, comm);
  free(mpi_pack_buffer); free(recvcounts); free(displs);

  message = Lmkvect(nil, fixnum_of_int(commsize-1));
  for (count = 0; count < commsize; ++count){
    mpi_pack_buffer = recvbuffer + displs[count];
    mpi_pack_size = recvcounts[count];
    elt(message, count) = unpack_object();
  }
  free(recvbuffer);
  return onevalue(message);
}

/* All to all scatter/gather.
 * (mpi_alltoall vector_of_messages comm)
 * returns vector of messages.
 */
static Lisp_Object Lmpi_alltoall(Lisp_Object nil, 
				 Lisp_Object smessages, Lisp_Object Lcomm)
{
  static char fun_name[] = "mpi_alltoall";

  Lisp_Object rmessages;
  int rank,comm, commsize, count;
  int *sendcounts, *recvcounts, *sdispls, *rdispls;
  char* recvbuffer;

  CSL_IGNORE(nil);
  check_fix(Lcomm);
  comm = int_of_fixnum(Lcomm);

  MPI_Comm_size(comm,&commsize);
  sendcounts = (int*)calloc(commsize, sizeof(int));
  recvcounts = (int*)calloc(commsize, sizeof(int));
  sdispls = (int*)calloc(commsize+1, sizeof(int));
  rdispls = (int*)calloc(commsize+1, sizeof(int));
  
  /* Call private functions in mpi_packing for consecutive packs */
  check_buffer = scatter_check_buffer;
  mpi_pack_offset = 0;
  mpi_pack_position = 0;
  mpi_pack_size = 0;
  mpi_buffer_bottom = 0;
  mpi_real_size = 0;
  for (count = 0; count < commsize; ++count){
    pack_cell(elt(smessages,count));
    sendcounts[count] = mpi_pack_position;
    mpi_pack_size -= mpi_pack_position;
    mpi_pack_offset += mpi_pack_position;
    mpi_pack_buffer += mpi_pack_position; 
    sdispls[count+1] = mpi_pack_offset;
    mpi_pack_position = 0;
  }
  check_buffer = default_check_buffer;
  
            MPI_Comm_rank(comm,&rank);

  MPI_Alltoall(sendcounts, 1, MPI_LONG, recvcounts, 1, MPI_LONG, comm);

  rdispls[0] = 0;
  for (count = 0; count < commsize; ++count)
    rdispls[count+1] = rdispls[count] + recvcounts[count];

  recvbuffer = (char*)malloc(rdispls[commsize]);

  MPI_Alltoallv(mpi_buffer_bottom, sendcounts, sdispls, MPI_PACKED,
		recvbuffer, recvcounts, rdispls, MPI_PACKED, comm);

  free(mpi_buffer_bottom); free(sendcounts); free(sdispls);

  rmessages = Lmkvect(nil, fixnum_of_int(commsize-1));
  for (count = 0; count < commsize; ++count){
    mpi_pack_buffer = recvbuffer + rdispls[count];
    mpi_pack_size = recvcounts[count];
    elt(rmessages, count) = unpack_object();
  }
  free(recvbuffer); free(recvcounts); free(rdispls);
  return onevalue(rmessages);
}

#else  /* USE_MPI */

static Lisp_Object Lmpi_comm_rank(Lisp_Object nil, Lisp_Object comm)
{
    return aerror0("mpi support not built into this version of CSL");
}

static Lisp_Object Lmpi_comm_size(Lisp_Object nil, Lisp_Object comm)
{
    return aerror0("mpi support not built into this version of CSL");
}

static Lisp_Object MS_CDECL Lmpi_send(Lisp_Object nil, int nargs, ...)
{
    return aerror0("mpi support not built into this version of CSL");
}

static Lisp_Object MS_CDECL Lmpi_recv(Lisp_Object nil, int nargs, ...) 
{
    return aerror0("mpi support not built into this version of CSL");
}

static Lisp_Object MS_CDECL Lmpi_sendrecv(Lisp_Object nil, int nargs, ...)
{
    return aerror0("mpi support not built into this version of CSL");
}

static Lisp_Object MS_CDECL Lmpi_isend(Lisp_Object nil, int nargs, ...)
{
    return aerror0("mpi support not built into this version of CSL");
}

static Lisp_Object MS_CDECL Lmpi_irecv(Lisp_Object nil, int nargs, ...)
{
    return aerror0("mpi support not built into this version of CSL");
}

static Lisp_Object Lmpi_wait(Lisp_Object nil, Lisp_Object request)
{
    return aerror0("mpi support not built into this version of CSL");
}


static Lisp_Object Lmpi_test(Lisp_Object nil, Lisp_Object request)
{
    return aerror0("mpi support not built into this version of CSL");
}

static Lisp_Object MS_CDECL Lmpi_iprobe(Lisp_Object nil, int nargs, ...)
{
    return aerror0("mpi support not built into this version of CSL");
}

static Lisp_Object MS_CDECL Lmpi_probe(Lisp_Object nil, int nargs, ...)
{
    return aerror0("mpi support not built into this version of CSL");
}

static Lisp_Object Lmpi_barrier(Lisp_Object nil, Lisp_Object comm)
{
    return aerror0("mpi support not built into this version of CSL");
}

static Lisp_Object MS_CDECL Lmpi_bcast(Lisp_Object nil, int nargs, ...)
{
    return aerror0("mpi support not built into this version of CSL");
}

static Lisp_Object MS_CDECL Lmpi_gather(Lisp_Object nil, int nargs, ...)
{
    return aerror0("mpi support not built into this version of CSL");
}

static Lisp_Object MS_CDECL Lmpi_scatter(Lisp_Object nil, int nargs, ...)
{
    return aerror0("mpi support not built into this version of CSL");
}


static Lisp_Object Lmpi_allgather(Lisp_Object nil, 
				  Lisp_Object message, 
				  Lisp_Object comm)
{
    return aerror0("mpi support not built into this version of CSL");
}

static Lisp_Object Lmpi_alltoall(Lisp_Object nil, 
				 Lisp_Object smessages, Lisp_Object Lcomm)
{
    return aerror0("mpi support not built into this version of CSL");
}

#endif /* USE_MPI */


setup_type const mpi_setup[] =
{
    {"mpi_comm_rank",         Lmpi_comm_rank, too_many_1,   wrong_no_1},
    {"mpi_comm_size",         Lmpi_comm_size, too_many_1,   wrong_no_1},
    {"mpi_send",              wrong_no_0a,    wrong_no_0b,  Lmpi_send},
    {"mpi_recv",              wrong_no_0a,    wrong_no_0b,  Lmpi_recv},
    {"mpi_sendrecv",          wrong_no_0a,    wrong_no_0b,  Lmpi_sendrecv},
    {"mpi_isend",             wrong_no_0a,    wrong_no_0b,  Lmpi_isend},
    {"mpi_irecv",             wrong_no_0a,    wrong_no_0b,  Lmpi_irecv},
    {"mpi_wait",              Lmpi_wait,      too_many_1,   wrong_no_1},
    {"mpi_test",              Lmpi_test,      too_many_1,   wrong_no_1},
    {"mpi_probe",             wrong_no_0a,    wrong_no_0b,  Lmpi_probe},
    {"mpi_iprobe",            wrong_no_0a,    wrong_no_0b,  Lmpi_iprobe},
    {"mpi_bcast",             wrong_no_0a,    wrong_no_0b,  Lmpi_bcast},
    {"mpi_gather",            wrong_no_0a,    wrong_no_0b,  Lmpi_gather},
    {"mpi_allgather",         wrong_no_0a,   Lmpi_allgather, wrong_no_2},
    {"mpi_scatter",           wrong_no_0a,    wrong_no_0b,  Lmpi_scatter},
    {"mpi_alltoall",          wrong_no_0a,    Lmpi_alltoall, wrong_no_2},
    {NULL,                    0, 0, 0}
};


/* end of cslmpi.c */