On Jun 30, 2011, at 2:48 PM, Rolf Rabenseifner wrote: Main decision that we must do: - How must we define -- MPI_Op_create (with a callback with choice buffer), and -- MPI_Errhandler_create (without such a choice buffer callback)? - Main question for this: Which rules do we have for callbacks and BIND(C)? (a full list of all callbacks are in MPI-2.2, page 617) Hopefully not we can move on to solving these final issues. -craig