MPI_Pack_size(3)                   Open MPI                   MPI_Pack_size(3)



NAME
       MPI_Pack_size - Returns the upper bound on the amount of space needed
       to pack a message.


SYNTAX
C Syntax
       #include <mpi.h>
       int MPI_Pack_size(int incount, MPI_Datatype datatype, MPI_Comm comm,
            int *size)


Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_PACK_SIZE(INCOUNT, DATATYPE, COMM, SIZE, IERROR)
            INTEGER   INCOUNT, DATATYPE, COMM, SIZE, IERROR


C++ Syntax
       #include <mpi.h>
       int Datatype::Pack_size(int incount, const Comm& comm) const


INPUT PARAMETERS
       incount   Count argument to packing call (integer).

       datatype  Datatype argument to packing call (handle).

       comm      Communicator argument to packing call (handle).


OUTPUT PARAMETERS
       size      Upper bound on size of packed message, in bytes (integer).

       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       MPI_Pack_size allows the application to find out how much space is
       needed to pack a message. A call to MPI_Pack_size(incount, datatype,
       comm, size) returns in size an upper bound on the increment in position
       that would occur in a call to MPI_Pack, with the same values for
       incount, datatype, and comm.

       Rationale:  The call returns an upper bound, rather than an exact
       bound, since the exact amount of space needed to pack the message may
       depend on the context (e.g., first message packed in a packing unit may
       take more space).


ERRORS
       Almost all MPI routines return an error value; C routines as the value
       of the function and Fortran routines in the last argument. C++
       functions do not return errors. If the default error handler is set to
       MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
       will be used to throw an MPI:Exception object.

       Before the error value is returned, the current MPI error handler is
       called. By default, this error handler aborts the MPI job, except for
       I/O function errors. The error handler may be changed with
       MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN
       may be used to cause error values to be returned. Note that MPI does
       not guarantee that an MPI program can continue past an error.


SEE ALSO
       MPI_Pack
       MPI_Unpack





1.4.1                            Jan 14, 2010                 MPI_Pack_size(3)
