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

       INCLUDE 'mpif.h'
       MPI_PACK_EXTERNAL_SIZE(DATAREP, INCOUNT, DATATYPE, SIZE, IERROR)

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

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