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NAME

       MPI_Alltoallv  -  Sends data from all to all processes; each process may  send a different
       amount of data and provide displacements for the input and output data.

SYNOPSIS

       int MPI_Alltoallv(void *sendbuf, int *sendcnts, int *sdispls,
                         MPI_Datatype sendtype, void *recvbuf, int *recvcnts,
                         int *rdispls, MPI_Datatype recvtype, MPI_Comm comm)

INPUT PARAMETERS

       sendbuf
              - starting address of send buffer (choice)
       sendcounts
              - integer array equal to the group size specifying the number of elements  to  send
              to each processor
       sdispls
              -  integer  array  (of  length  group  size).  Entry  j  specifies the displacement
              (relative to sendbuf  from which to take the outgoing data destined for process j

       sendtype
              - data type of send buffer elements (handle)
       recvcounts
              - integer array equal to the group size specifying the maximum number  of  elements
              that can be received from each processor
       rdispls
              -  integer  array  (of  length  group  size).  Entry  i  specifies the displacement
              (relative to recvbuf  at which to place the incoming data from process i

       recvtype
              - data type of receive buffer elements (handle)
       comm   - communicator (handle)

OUTPUT PARAMETER

       recvbuf
              - address of receive buffer (choice)

THREAD AND INTERRUPT SAFETY

       This routine is thread-safe.  This means that this routine may be safely used by  multiple
       threads  without the need for any user-provided thread locks.  However, the routine is not
       interrupt safe.  Typically, this is due to the use of memory allocation routines  such  as
       malloc or other non-MPICH runtime routines that are themselves not interrupt-safe.

NOTES FOR FORTRAN

       All  MPI  routines  in  Fortran  (except  for MPI_WTIME and MPI_WTICK ) have an additional
       argument ierr at the end of the argument list.  ierr  is  an  integer  and  has  the  same
       meaning  as  the  return  value  of  the  routine  in  C.   In  Fortran,  MPI routines are
       subroutines, and are invoked with the call statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran.

ERRORS

       All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error value;  C  routines  as
       the  value of the function and Fortran routines in the last argument.  Before the value is
       returned, the current MPI error handler is called.  By default, this error handler  aborts
       the  MPI  job.   The  error  handler  may  be  changed  with  MPI_Comm_set_errhandler (for
       communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler  (for  RMA
       windows).   The  MPI-1  routine  MPI_Errhandler_set may be used but its use is deprecated.
       The predefined error handler MPI_ERRORS_RETURN may be used to cause  error  values  to  be
       returned.   Note  that  MPI  does  not  guarentee that an MPI program can continue past an
       error; however, MPI implementations will attempt to continue whenever possible.

       MPI_ERR_COMM
              - Invalid communicator.  A common error is to use a null  communicator  in  a  call
              (not even allowed in MPI_Comm_rank ).
       MPI_ERR_COUNT
              - Invalid count argument.  Count arguments must be non-negative; a count of zero is
              often valid.
       MPI_ERR_TYPE
              -  Invalid  datatype  argument.   May   be   an   uncommitted   MPI_Datatype   (see
              MPI_Type_commit ).
       MPI_ERR_BUFFER
              - Invalid buffer pointer.  Usually a null buffer where one is not valid.

LOCATION

       alltoallv.c

                                            1/21/2011                            MPI_Alltoallv(3)