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MPI_Alltoallv(3)			     LAM/MPI				 MPI_Alltoallv(3)

       MPI_Alltoallv -	Sends data from all to all processes, with a displacement

       #include <mpi.h>
       int MPI_Alltoallv(void *sbuf, int *scounts, int *sdisps,
	   MPI_Datatype sdtype, void *rbuf, int *rcounts,
	   int *rdisps, MPI_Datatype rdtype,
	   MPI_Comm comm)

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

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

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

       rbuf   - address of receive buffer (choice)

       The  receive  buffer  rbuf needs to be large enough to hold the data that will be received
       from all processes.

       LAM/MPI does not yet support invoking this function on a communicator that contains  ranks
       that are non-local IMPI procs.

       All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have an additional argu-
       ment 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.

       If an error occurs in an MPI function, the current MPI error handler is called  to  handle
       it.   By default, this error handler aborts the MPI job.  The error handler may be changed
       with MPI_Errhandler_set ; the predefined error handler MPI_ERRORS_RETURN may  be  used  to
       cause  error values to be returned (in C and Fortran; this error handler is less useful in
       with the C++ MPI bindings.   The  predefined  error  handler  MPI::ERRORS_THROW_EXCEPTIONS
       should  be  used in C++ if the error value needs to be recovered).  Note that MPI does not
       guarantee that an MPI program can continue past an error.

       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.  The C++ bindings for
       MPI do not return error values; instead, error values are communicated by throwing  excep-
       tions  of  type	MPI::Exception	(but  not by default).	Exceptions are only thrown if the
       error value is not MPI::SUCCESS

       Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI functions will return
       upon an error, there will be no way to recover what the actual error value was.
	      -  Invalid  communicator.   A  common error is to use a null communicator in a call
	      (not even allowed in MPI_Comm_rank ).
	      - Invalid communicator.  LAM/MPI does  not  yet  support	invoking  collectives  on
	      - A communicator that contains some non-local IMPI procs was used for some function
	      which has not yet had the IMPI extensions implemented yet.  For example, most  col-
	      lectives on IMPI communicators have not been implemented yet.
	      - Invalid count argument.  Count arguments must be non-negative; a count of zero is
	      often valid.
	      - Invalid datatype argument.  May be an uncommitted MPI_Datatype (see MPI_Type_com-
	      mit ).
	      - Invalid buffer pointer.  Usually a null buffer where one is not valid.

       For  more information, please see the official MPI Forum web site, which contains the text
       of both the MPI-1 and MPI-2 standards.  These documents contain detailed information about
       each MPI function (most of which is not duplicated in these man pages).


       The  LAM  Team  would  like the thank the MPICH Team for the handy program to generate man
       pages ("doctext" from ftp://ftp.mcs.anl.gov/pub/sowing/sowing.tar.gz ), the  initial  for-
       matting, and some initial text for most of the MPI-1 man pages.


LAM/MPI 6.5.8				    11/10/2002				 MPI_Alltoallv(3)
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