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MPI_Comm_create_keyval(3OpenMPI)                                            MPI_Comm_create_keyval(3OpenMPI)



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 pre-defined predefined
       defined 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
Open MPI 1.2                                   September 2006               MPI_Comm_create_keyval(3OpenMPI)