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

Fortran 2008 Syntax

       USE mpi_f08
       MPI_Register_datarep(datarep, read_conversion_fn, write_conversion_fn,
                 dtype_file_extent_fn, extra_state, ierror)
            CHARACTER(LEN=*), INTENT(IN) :: datarep
            PROCEDURE(MPI_Datarep_conversion_function) :: read_conversion_fn
            PROCEDURE(MPI_Datarep_conversion_function) :: write_conversion_fn
            PROCEDURE(MPI_Datarep_extent_function) :: dtype_file_extent_fn
            INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: extra_state
            INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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.

4.1.6                                             Sep 30, 2023                           MPI_Register_datarep(3)