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)

       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

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