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NAME

       MPI_Comm_free_keyval - Frees attribute key for communicator cache attribute.

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Comm_free_keyval(int *comm_keyval)

Fortran Syntax

       INCLUDE 'mpif.h'
       MPI_COMM_FREE_KEYVAL(COMM_KEYVAL, IERROR)
            INTEGER   COMM_KEYVAL, IERROR

C++ Syntax

       #include <mpi.h>
       static void MPI::Comm::Free_keyval(int& comm_keyval)

INPUT/OUTPUT PARAMETER

       comm_keyval

OUTPUT PARAMETER

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       MPI_Comm_free_keyval frees an extant attribute key. This function sets the value of keyval
       to  MPI_KEYVAL_INVALID. Note that it is not erroneous to free an attribute key that is  in
       use,  because  the  actual  free  does  not transpire until after all references (in other
       communicators on the process) to the key have been freed.  These  references  need  to  be
       explictly  freed  by  the  program, either via calls to MPI_Comm_delete_attr that free one
       attribute instance, or by  calls  to  MPI_Comm_free  that  free  all  attribute  instances
       associated with the freed communicator.

       This  call  is  identical  to  the  call  MPI_Keyval_free  but  is  needed  to  match  the
       communicator-specific creation function introduced in  the  MPI-2  standard.  The  use  of
       MPI_Keyval_free is deprecated.

NOTES

       Key values are global (they can be used with any and all communicators).

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.