MPI_Comm_create_keyval - Generates a new communicator
       attribute key


SYNOPSIS

       C:

            #include <mpi.h>

            int MPI_Comm_create_keyval ( comm_copy_attr_fn, comm_delete_attr_fn, comm_keyval,
            extra_state)
            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:

            INCLUDE "mpif.h" (or USE MPI)

            EXTERNAL comm_copy_attr_fn, comm_delete_attr_fn
            INTEGER keyval, ierror
            INTEGER(KIND=MPI_ADDRESS_KIND) extra_state

            CALL MPI_COMM_CREATE_KEYVAL(comm_copy_attr_fn, comm_delete_attr_fn, comm_keyval,
            extra_state, ierror)


STANDARDS

       This function is defined in the MPI-2 standard.

       This release implements the MPI 1.2 standard, as
       documented by the MPI Forum in the spring 1997 release of
       MPI:  A Message Passing Interface Standard.


DESCRIPTION

       The MPI_Comm_create_keyval routine generates a new
       communicator attribute key.  This function replaces
       MPI_Keyval_create which has been deprecated.  This routine
       accepts the following parameters:

       comm_copy_attr_fn
                      Specifies the copy callback function for
                      keyval

       comm_delete_attr_fn
                      Specifies the delete callback function for
                      keyval

       extra_state    Specifies an extra state for callback
                      functions

       keyval         Returns the key value for future access


       ierror         Specifies the return code value for
                      successful completion, which is in
                      MPI_SUCCESS.  MPI_SUCCESS is defined in the
                      mpif.h file.


NOTES

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

       There are subtle differences between C and Fortran that
       require that comm_copy_attr_fn be written in the same
       language as that from which
        MPI_Comm_create_keyval is called.  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.  Also, the attribute types for Fortran call
       back functions are integers of kind MPI_ADDRESS_KIND.
       Note this is different from the callback routines used
       with the deprecated MPI_Keyval_create routine.   Thus,
       replacement of calls to the Fortran version of
       MPI_Keyval_create with MPI_Comm_create_keyval may require
       changes to the accompanying callback functions.


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