MPI_Pack_external_size(3)          Open MPI          MPI_Pack_external_size(3)



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




1.4.1                            Jan 14, 2010        MPI_Pack_external_size(3)
