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