MPI_Comm_create_keyval(3)          Open MPI          MPI_Comm_create_keyval(3)



NAME
       MPI_Comm_create_keyval - Generates a new attribute key.


SYNTAX
C Syntax
       #include <mpi.h>
       int MPI_Comm_create_keyval(MPI_Comm_copy_attr_function
            *comm_copy_attr_fn, MPI_Comm_delete_attr_function
            *comm_delete_attr_fn, int *comm_keyval,
            void *extra_state)


Fortran Syntax (see FORTRAN 77 NOTES)
       INCLUDE 'mpif.h'
       MPI_COMM_CREATE_KEYVAL(COMM_COPY_ATTR_FN, COMM_DELETE_ATTR_FN,
            COMM_KEYVAL, EXTRA_STATE, IERROR)

           EXTERNAL COMM_COPY_ATTR_FN, COMM_DELETE_ATTR_FN
           INTEGER COMM_KEYVAL, IERROR
           INTEGER(KIND=MPI_ADDRESS_KIND) EXTRA_STATE


C++ Syntax
       #include <mpi.h>
       static in MPI::Comm::Create_keyval(MPI::Comm::Copy_attr_function*
            comm_copy_attr_fn,
            MPI::Comm::Delete_attr_function* comm_delete_attr_fn,
            void* extra_state)


INPUT PARAMETERS
       comm_copy_attr_fn
                 Copy callback function for comm_keyval (function).

       comm_delete_attr_fn
                 Delete callback function for comm_keyval (function).

       extra_state
                 Extra state for callback functions.


OUTPUT PARAMETER
       comm_keyval
                 Key value for future access (integer).

       IERROR    Fortran only: Error status (integer).


DESCRIPTION
       This function replaces MPI_Keyval_create, the use of which is
       deprecated. The C binding is identical. The Fortran binding differs in
       that extra_state is an address-sized integer. Also, the copy and delete
       callback functions have Fortran bindings that are consistent with
       address-sized attributes.

       The argument comm_copy_attr_fn may be specified as
       MPI_COMM_NULL_COPY_FN or MPI_COMM_DUP_FN from C, C++, or Fortran.
       MPI_COMM_NULL_COPY_FN is a function that does nothing more than
       returning flag = 0 and MPI_SUCCESS. MPI_COMM_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. These replace the MPI-1
       predefined callbacks MPI_NULL_COPY_FN and MPI_DUP_FN, the use of which
       is deprecated.

       The C callback functions are:

       typedef int MPI_Comm_copy_attr_function(MPI_Comm oldcomm, int comm_keyval,
                    void *extra_state, void *attribute_val_in,
                    void *attribute_val_out, int *flag);
       and
       typedef int MPI_Comm_delete_attr_function(MPI_Comm comm, int comm_keyval,
                    void *attribute_val, void *extra_state);

       which are the same as the MPI-1.1 calls but with a new name. The old
       names are deprecated.

       The Fortran callback functions are:

       SUBROUTINE COMM_COPY_ATTR_FN(OLDCOMM, COMM_KEYVAL, EXTRA_STATE,
                    ATTRIBUTE_VAL_IN, ATTRIBUTE_VAL_OUT, FLAG, IERROR)
           INTEGER OLDCOMM, COMM_KEYVAL, IERROR
           INTEGER(KIND=MPI_ADDRESS_KIND) EXTRA_STATE, ATTRIBUTE_VAL_IN,
               ATTRIBUTE_VAL_OUT
           LOGICAL FLAG
       and
       SUBROUTINE COMM_DELETE_ATTR_FN(COMM, COMM_KEYVAL, ATTRIBUTE_VAL, EXTRA_STATE,
                    IERROR)
           INTEGER COMM, COMM_KEYVAL, IERROR
           INTEGER(KIND=MPI_ADDRESS_KIND) ATTRIBUTE_VAL, EXTRA_STATE

       The C++ callbacks are:

       typedef int MPI::Comm::Copy_attr_function(const MPI::Comm& oldcomm,
                    int comm_keyval, void* extra_state, void* attribute_val_in,
                    void* attribute_val_out, bool& flag);
       and
       typedef int MPI::Comm::Delete_attr_function(MPI::Comm& comm,
                    int comm_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 the MPI man page for a full list of MPI error codes.


SEE ALSO
1.4.1                            Jan 14, 2010        MPI_Comm_create_keyval(3)
