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

       USE MPI
       ! or the older form: INCLUDE 'mpif.h'
       MPI_PACK_SIZE(INCOUNT, DATATYPE, COMM, SIZE, IERROR)
            INTEGER   INCOUNT, DATATYPE, COMM, SIZE, IERROR

Fortran 2008 Syntax

       USE mpi_f08
       MPI_Pack_size(incount, datatype, comm, size, ierror)
            INTEGER, INTENT(IN) :: incount
            TYPE(MPI_Datatype), INTENT(IN) :: datatype
            TYPE(MPI_Comm), INTENT(IN) :: comm
            INTEGER, INTENT(OUT) :: size
            INTEGER, OPTIONAL, INTENT(OUT) :: 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