NAME

       MPI_Type_create_keyval - Generates a new attribute key for caching on data types.

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Type_create_keyval(MPI_Type_copy_attr_function *type_copy_attr_fn,
            MPI_Type_delete_attr_function *type_delete_attr_fn,
            int *type_keyval, void *extra_state)

Fortran Syntax (see FORTRAN 77 NOTES)

       USE MPI
       ! or the older form: INCLUDE 'mpif.h'
       MPI_TYPE_CREATE_KEYVAL(TYPE_COPY_ATTR_FN, TYPE_DELETE_ATTR_FN,
                 TYPE_KEYVAL, EXTRA_STATE, IERROR)
            EXTERNAL TYPE_COPY_ATTR_FN, TYPE_DELETE_ATTR_FN
            INTEGER   TYPE_KEYVAL, IERROR
            INTEGER(KIND=MPI_ADDRESS_KIND) EXTRA_STATE

Fortran 2008 Syntax

       USE mpi_f08
       MPI_Type_create_keyval(type_copy_attr_fn, type_delete_attr_fn, type_keyval,
                 extra_state, ierror)
            PROCEDURE(MPI_Type_copy_attr_function) :: type_copy_attr_fn
            PROCEDURE(MPI_Type_delete_attr_function) :: type_delete_attr_fn
            INTEGER, INTENT(OUT) :: type_keyval
            INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: extra_state
            INTEGER, OPTIONAL, INTENT(OUT) :: ierror

C++ Syntax

       #include <mpi.h>
       static int MPI::Datatype::Create_keyval(MPI::Datatype::Copy_attr_function*
            type_copy_attr_fn, MPI::Datatype::Delete_attr_function*
            type_delete_attr_fn, void* extra_state)

INPUT PARAMETERS

       type_copy_attr_fn
                 Copy callback function for type_keyval (function).

       type_delete_attr_fn
                 Delete callback function for type_keyval (function).

       extra_state
                 Extra state for callback functions.

OUTPUT PARAMETERS

       type_keyval
                 Key value for future access (integer).

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       MPI_Type_create_keyval  generates  a  new attribute key for caching on data types. This routine partially
       replaces MPI_Keyval_create.

       The argument type_copy_attr_fn may be specified as MPI_TYPE_NULL_COPY_FN or MPI_TYPE_DUP_FN from C,  C++,
       or  Fortran.  MPI_TYPE_NULL_COPY_FN  is  a  function  that does nothing other than returning flag = 0 and
       MPI_SUCCESS. MPI_TYPE_DUP_FN is a simple-minded copy function that sets flag = 1, returns  the  value  of
       attribute_val_in in attribute_val_out, and returns MPI_SUCCESS.

       The  argument  type_delete_attr_fn  may  be specified as MPI_TYPE_NULL_DELETE_FN from C, C++, or Fortran.
       MPI_TYPE_NULL_DELETE_FN is a function that does nothing beyond returning  MPI_SUCCESS.   The  C  callback
       functions are:

       typedef int MPI_Type_copy_attr_function(MPI_Datatype oldtype,
                   int type_keyval, void *extra_state, void *attribute_val_in,
                   void *attribute_val_out, int *flag);
       and
       typedef int MPI_Type_delete_attr_function(MPI_Datatype type, int type_keyval,
                    void *attribute_val, void *extra_state);

       The Fortran callback functions are:

       SUBROUTINE TYPE_COPY_ATTR_FN(OLDTYPE, TYPE_KEYVAL, EXTRA_STATE,
                    ATTRIBUTE_VAL_IN, ATTRIBUTE_VAL_OUT, FLAG, IERROR)
           INTEGER OLDTYPE, TYPE KEYVAL, IERROR
           INTEGER(KIND=MPI_ADDRESS_KIND) EXTRA_STATE,
               ATTRIBUTE_VAL_IN, ATTRIBUTE_VAL_OUT
           LOGICAL FLAG
       and
       SUBROUTINE TYPE_DELETE_ATTR_FN(TYPE, TYPE_KEYVAL, ATTRIBUTE_VAL, EXTRA_STATE,
                    IERROR)
           INTEGER TYPE, TYPE_KEYVAL, IERROR
           INTEGER(KIND=MPI_ADDRESS_KIND) ATTRIBUTE VAL, EXTRA_STATE

       The C++ callbacks are:

       typedef int MPI::Datatype::Copy_attr_function(const MPI::Datatype& oldtype,
                    int type_keyval, void* extra_state,
                    const void* attribute_val_in, void* attribute_val_out,
                    bool& flag);
       and
       typedef int MPI::Datatype::Delete_attr_function(MPI::Datatype& type,
                    int type_keyval, void* attribute_val, void* extra_state);

FORTRAN 77 NOTES

       The  MPI  standard  prescribes  portable Fortran syntax for the EXTRA_STATE argument only for Fortran 90.
       FORTRAN 77 users may use the non-portable syntax

            INTEGER*MPI_ADDRESS_KIND EXTRA_STATE

       where MPI_ADDRESS_KIND is a constant defined in mpif.h and gives the length of the  declared  integer  in
       bytes.

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 ALSO

       MPI_Type_free_keyval

4.1.6                                             Sep 30, 2023                         MPI_Type_create_keyval(3)