MPI_Keyval_create(3)               Open MPI               MPI_Keyval_create(3)



NAME
       MPI_Keyval_create - Generates a new attribute key -- use of this
       routine is deprecated.


SYNTAX
C Syntax
       #include <mpi.h>
       int MPI_Keyval_create(MPI_Copy_function *copy_fn,
            MPI_Delete_function *delete_fn, int *keyval, void *extra_state)


Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_KEYVAL_CREATE(COPY_FN, DELETE_FN, KEYVAL, EXTRA_STATE, IERROR)
            EXTERNAL  COPY_FN, DELETE_FN
            INTEGER   KEYVAL, EXTRA_STATE, IERROR



INPUT PARAMETERS
       copy_fn   Copy callback function for keyval.

       delete_fn Delete callback function for keyval.

       extra_state
                 Extra state for callback functions.


OUTPUT PARAMETERS
       keyval    Key value for future access (integer).

       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       Note that use of this routine is deprecated as of MPI-2. Please use
       MPI_Comm_create_keyval instead.

       This deprecated routine is not available in C++.

       Generates a new attribute key. Keys are locally unique in a process and
       opaque to the user, though they are explicitly stored in integers. Once
       allocated, the key value can be used to associate attributes and access
       them on any locally defined communicator.

       The copy_fn function is invoked when a communicator is duplicated by
       MPI_COMM_DUP. copy_fn should be of type MPI_Copy_function, which is
       defined as follows:

         typedef int MPI_Copy_function(MPI_Comm oldcomm, int keyval,
                                       void *extra_state, void *attribute_val_in,
                                       void *attribute_val_out, int *flag)

       A Fortran declaration for such a function is as follows:

         SUBROUTINE COPY_FUNCTION(OLDCOMM, KEYVAL, EXTRA_STATE, ATTRIBUTE_VAL_IN,
                     ATTRIBUTE_VAL_OUT, FLAG, IERR)
         INTEGER OLDCOMM, KEYVAL, EXTRA_STATE,
         ATTRIBUTE_VAL_IN, ATTRIBUTE_VAL_OUT, IERR
         LOGICAL FLAG

       The copy callback function is invoked for each key value in oldcomm in
       arbitrary order. Each call to the copy callback is made with a key
       value and its corresponding attribute. If it returns flag = 0, then the
       attribute is deleted in the duplicated communicator. Otherwise ( flag =
       1), the new attribute value is set to the value returned in
       attribute_val_out. The function returns MPI_SUCCESS on success and an
       error code on failure (in which case MPI_Comm_dup will fail).

       copy_fn may be specified as MPI_NULL_COPY_FN or MPI_DUP_FN from either
       C or Fortran; MPI_NULL_COPY_FN is a function that does nothing other
       than return flag = 0, and MPI_SUCCESS. MPI_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.


NOTES
       Key values are global (available for any and all communicators).

       There are subtle differences between C and Fortran that require that
       the copy_fn be written in the same language that MPI_Keyval_create is
       called from. This should not be a problem for most users; only
       programers using both Fortran and C in the same program need to be sure
       that they follow this rule.

       Even though both formal arguments attribute_val_in and
       attribute_val_out are of type void*, their usage differs. The C copy
       function is passed by MPI in attribute_val_in the value of the
       attribute, and in attribute_val_out the address of the attribute, so as
       to allow the function to return the (new) attribute value. The use of
       type void* for both is to avoid messy type casts.

       A valid copy function is one that completely duplicates the information
       by making a full duplicate copy of the data structures implied by an
       attribute; another might just make another reference to that data
       structure, while using a reference-count mechanism. Other types of
       attributes might not copy at all (they might be specific to oldcomm
       only).

       Analogous to copy_fn is a callback deletion function, defined as
       follows. The delete_fn function is invoked when a communicator is
       deleted by MPI_Comm_free or when a call is made explicitly to
       MPI_Attr_delete. delete_fn should be of type MPI_Delete_function, which
       is defined as follows:

         typedef int MPI_Delete_function(MPI_Comm comm, int keyval,
             void *attribute_val, void *extra_state);

       A Fortran declaration for such a function is as follows:

         SUBROUTINE DELETE_FUNCTION(COMM, KEYVAL,ATTRIBUTE_VAL, EXTRA_STATE, IERR)
             INTEGER COMM, KEYVAL, ATTRIBUTE_VAL, EXTRA_STATE, IERR

       This function is called by MPI_Comm_free, MPI_Attr_delete, and
       MPI_Attr_put to do whatever is needed to remove an attribute. The
       function returns MPI_SUCCESS on success and an error code on failure
       (in which case MPI_COMM_FREE will fail).

       delete_fn may be specified as MPI_NULL_DELETE_FN from either C or
       FORTRAN; MPI_NULL_DELETE_FN is a function that does nothing, other than
       returning MPI_SUCCESS.

       The special key value MPI_KEYVAL_INVALID is never returned by
       MPI_Keyval_create. Therefore, it can be used for static initialization
       of key values.


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_Keyval_free



1.4.1                            Jan 14, 2010             MPI_Keyval_create(3)
