MPI_PACK_EXTERNAL_SIZE(3)          Open MPI          MPI_PACK_EXTERNAL_SIZE(3)


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(const 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

INPUT PARAMETERS

       o datarep: Data representation (string).

       o incount: Number of input data items (integer).

       o datatype: Datatype of each input data item (handle).

OUTPUT PARAMETERS

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

       o 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 return
       result of the function and Fortran routines in the last argument.

       Before the error value is returned, the current MPI error handler
       associated with the communication object (e.g., communicator, window,
       file) is called.  If no communication object is associated with the MPI
       call, then the call is considered attached to MPI_COMM_SELF and will
       call the associated MPI error handler. When MPI_COMM_SELF is not
       initialized (i.e., before MPI_Init/MPI_Init_thread, after MPI_Finalize,
       or when using the Sessions Model exclusively) the error raises the
       initial error handler. The initial error handler can be changed by
       calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World
       model, or the mpi_initial_errhandler CLI argument to mpiexec or info
       key to MPI_Comm_spawn/MPI_Comm_spawn_multiple.  If no other appropriate
       error handler has been set, then the MPI_ERRORS_RETURN error handler is
       called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is
       called for all other MPI functions.

       Open MPI includes three predefined error handlers that can be used:

       o MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI
         processes.

       o MPI_ERRORS_ABORT An error handler that can be invoked on a
         communicator, window, file, or session. When called on a
         communicator, it acts as if MPI_Abort was called on that
         communicator. If called on a window or file, acts as if MPI_Abort was
         called on a communicator containing the group of processes in the
         corresponding window or file. If called on a session, aborts only the
         local process.

       o MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by
       calling:

       o MPI_Comm_create_errhandler then MPI_Comm_set_errhandler

       o MPI_File_create_errhandler then MPI_File_set_errhandler

       o MPI_Session_create_errhandler then MPI_Session_set_errhandler or at
         MPI_Session_init

       o MPI_Win_create_errhandler then MPI_Win_set_errhandler

       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 the Error Handling section of the MPI-3.1 standard for more
       information.

       SEE ALSO:

          o MPI_Pack_external

          o MPI_Unpack_external

COPYRIGHT
       2003-2024, The Open MPI Community

                               February 6, 2024      MPI_PACK_EXTERNAL_SIZE(3)