NAME

       MPI_Pack_external_size - Calculates upper bound on space needed to write to a portable format

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Pack_external_size(char *datarep, int incount,
            MPI_Datatype datatype, MPI_Aint *size)

Fortran Syntax

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

            INTEGER        INCOUNT, DATATYPE, IERROR
            INTEGER(KIND=MPI_ADDRESS_KIND) SIZE
            CHARACTER*(*)  DATAREP

Fortran 2008 Syntax

       USE mpi_f08
       MPI_Pack_external_size(datarep, incount, datatype, size, ierror)
            TYPE(MPI_Datatype), INTENT(IN) :: datatype
            INTEGER, INTENT(IN) :: incount
            CHARACTER(LEN=*), INTENT(IN) :: datarep
            INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(OUT) :: size
            INTEGER, OPTIONAL, INTENT(OUT) :: ierror

C++ Syntax

       #include <mpi.h>
       MPI::Aint MPI::Datatype::Pack_external_size(const char* datarep,
            int incount) const

INPUT PARAMETERS

       datarep   Data representation (string).

       incount   Number of input data items (integer).

       datatype  Datatype of each input data item (handle).

OUTPUT PARAMETERS

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

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       MPI_Pack_external_size  allows  the application to find out how much space is needed to pack a message in
       the portable format defined by the MPI Forum. It returns in size an  upper  bound  on  the  increment  in
       position  that  would occur in a call to MPI_Pack_external with the same values for datarep, incount, and
       datatype.

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

NOTES

       The datarep argument specifies the data format. The only valid value in the current  version  of  MPI  is
       "external32". The argument is provided for future extensibility.

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 the MPI man page for a full list of MPI error codes.

SEE ALSO

       MPI_Pack_external
       MPI_Unpack_external