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MPI_Allgatherv(3)			     LAM/MPI				MPI_Allgatherv(3)

       MPI_Allgatherv -  Gathers data from all tasks and deliver it to all

       #include <mpi.h>
       int MPI_Allgatherv(void *sbuf, int scount, MPI_Datatype sdtype,
	    void * rbuf, int *rcounts, int *disps,
	    MPI_Datatype rdtype, MPI_Comm comm)

       sbuf   - starting address of send buffer (choice)
       scount - number of elements in send buffer (integer)
       sdtype - data type of send buffer elements (handle)
	      -  integer  array (of length group size) containing the number of elements that are
	      received from each process
       disps  - 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 MPI standard (1.0 and 1.1) says that

       "The  jth  block  of data sent from each proess is received by every process and placed in
       the jth block of the buffer recvbuf."

       This is misleading; a better description is

       "The block of data sent from the jth process is received by every process  and  placed  in
       the jth block of the buffer recvbuf."

       This text was suggested by Rajeev Thakur.

       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 buffer pointer.  Usually a null buffer where one is not valid.
	      - 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 ).

       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_Allgatherv(3)
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