NAME

       MPI_Register_datarep - Defines data representation.

SYNTAX

C Syntax

       #include       <mpi.h>       int       MPI_Register_datarep(const      char      *datarep,
            MPI_Datarep_conversion_function                                  *read_conversion_fn,
            MPI_Datarep_conversion_function                                 *write_conversion_fn,
            MPI_Datarep_extent_function *dtype_file_extent_fn,      void *extra_state)

Fortran Syntax

       USE MPI
       ! or the older form: INCLUDE 'mpif.h'
       MPI_REGISTER_DATAREP(DATAREP, READ_CONVERSION_FN,
            WRITE_CONVERSION_FN, DTYPE_FILE_EXTENT_FN,
            EXTRA_STATE, IERROR)
            CHARACTER*(*)  DATAREP
            EXTERNAL  READ_CONVERSION_FN, WRITE_CONVERSION_FN, DTYPE_FILE_EXTENT_FN
            INTEGER   IERROR
            INTEGER(KIND=MPI_ADDRESS_KIND)     EXTRA_STATE

C++ Syntax

       #include <mpi.h>
       void MPI::Register_datarep(const char* datarep,
            MPI::Datarep_conversion_function* read_conversion_fn,
            MPI::Datarep_conversion_function* write_conversion_fn,
            MPI::Datarep_extent_function* dtype_file_extent_fn,
            void* extra_state)

INPUT PARAMETERS

       datarep   Data representation identifier (string).

       read_conversion_fn
                 Function invoked to convert from file representation  to  native  representation
                 (function).

       write_conversion_fn
                 Function  invoked  to  convert from native representation to file representation
                 (function).

       dtype_file_extent_fn
                 Function invoked to get the extent of a data type as  represented  in  the  file
                 (function).

       extra_state
                 Extra state.

OUTPUT PARAMETER

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       MPI_Register_datarep   defines   a   data   representation.   It   associates   the   data
       representation's  identifier  (a  string)  with  the  functions  that  convert  from  file
       representation  to  the  native representation and vice versa, with the function that gets
       the extent of a data type as represented in the file, as well as with "extra state," which
       is  used  for passing arguments. Once a data representation has been registered using this
       routine, you may specify its identifier  as  an  argument  to  MPI_File_set_view,  causing
       subsequent data-access operations to call the specified conversion functions.

       The call associates read_conversion_fn, write_conversion_fn, and dtype_file_extent_fn with
       the data representation identifier datarep. datarep can then be used  as  an  argument  to
       MPI_File_set_view,  causing  subsequent  data  access  operations  to  call the conversion
       functions to convert all data items accessed between file data representation  and  native
       representation.  MPI_Register_datarep  is  a  local  operation and only registers the data
       representation for the calling MPI process. If datarep is already defined, an error in the
       error class MPI_ERR_DUP_DATAREP is raised using the default file error handler. The length
       of a data representation  string  is  limited  to  the  value  of  MPI_MAX_DATAREP_STRING.
       MPI_MAX_DATAREP_STRING  must  have  a  value  of  at least 64. No routines are provided to
       delete data representations and free the associated resources; it is not expected that  an
       application will generate them in significant numbers.

NOTES

       The  Fortran  version  of each MPI I/O routine includes a final argument, IERROR, which is
       not defined in the PARAMETERS sections. This argument is used to return the  error  status
       of the routine in the manner typical for Fortran library routines.

       The C version of each routine returns an error status as an integer return value.

       Error classes are found in mpi.h (for C), mpif.h (for Fortran), and mpi++.h (for C++).

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. For  MPI  I/O
       function  errors, the default error handler is set to MPI_ERRORS_RETURN. The error handler
       may   be   changed   with   MPI_File_set_errhandler;   the   predefined   error    handler
       MPI_ERRORS_ARE_FATAL  may  be  used  to  make  I/O  errors  fatal.  Note that MPI does not
       guarantee that an MPI program can continue past an error.