While updating petsc4py for the latest DMDA chages, and alto taking into account some new in NumPy C API related to neighborhood iterators, I've got new idea. What about the API below?: enum DMDABoundaryType: DMDA_BOUNDARY_NONE = 0 DMDA_BOUNDARY_GHOSTED = 1 DMDA_BOUNDARY_MIRROR = 2 DMDA_BOUNDARY_PERIODIC = 4 PetscErrorCode DMDASetBoundaryType(DM dm, DMDABoundaryType bx, DMDABoundaryType by, DMDABoundaryType bz) Changes for GHOSTED and PERIODIC should be easy (http://lkml.org/lkml/2000/8/25/132) ;-). The new MIRROR boundary type could be implemented later. -- Lisandro Dalcin --------------- CIMEC (INTEC/CONICET-UNL) Predio CONICET-Santa Fe Colectora RN 168 Km 472, Paraje El Pozo 3000 Santa Fe, Argentina Tel: +54-342-4511594 (ext 1011) Tel/Fax: +54-342-4511169