NAME

       MPI_Gatherv -  Gathers into specified locations from all processes in a group

SYNOPSIS

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

INPUT PARAMETERS

       sendbuf
              - starting address of send buffer (choice)
       sendcount
              - number of elements in send buffer (integer)
       sendtype
              - data type of send buffer elements (handle)
       recvcounts
              -  integer  array  (of length group size) containing the number of elements that are received from
              each process (significant only at root )
       displs - integer array (of length group size). Entry i specifies the displacement relative to recvbuf  at
              which to place the incoming data from process i (significant only at root)
       recvtype
              - data type of recv buffer elements (significant only at root ) (handle)
       root   - rank of receiving process (integer)
       comm   - communicator (handle)

OUTPUT PARAMETER

       recvbuf
              - address of receive buffer (choice, significant only at root )

USAGE WITH IMPI EXTENSIONS

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

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

       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  exceptions  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.
       MPI_SUCCESS
              - No error; MPI routine completed successfully.
       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_OTHER
              - A collective implementation was not able to be located at run-time for this communicator.
       MPI_ERR_OTHER
              - 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 collectives on IMPI communicators
              have not been implemented yet.
       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.
       MPI_ERR_ROOT
              - Invalid root.  The root must be specified as a rank in the communicator.  Ranks must be  between
              zero and the size of the communicator minus one.
       MPI_ERR_ARG
              -  Invalid  argument.   Some  argument is invalid and is not identified by a specific error class.
              This is typically a NULL pointer or other such error.

MORE INFORMATION

       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).

       http://www.mpi-forum.org/

ACKNOWLEDGEMENTS

       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 formatting, and some initial text  for
       most of the MPI-1 man pages.

LOCATION

       gatherv.c

LAM/MPI 7.1.4                                       6/24/2006                                     MPI_Gatherv(3)