If you already have the overlapping subdomain, you do not have to set the non-overlapping subdomain.  If you already passed the overlapping subdomain, you could not increase the overlap any more (however, we could enable this very easily, but no many user cases, I think). 

On Sun, Jul 3, 2016 at 10:45 AM, Mark Adams <mfadams@lbl.gov> wrote:

PetscErrorCode  PCASMSetLocalSubdomains(PC pc,PetscInt n,IS is[],IS is_local[])

"is" is the overlapping subdomain, and "is_local" is the subdomain without overlap.

So if I have some overlapping subdomains (I don't) I would have to prune the IS to get some non-overlapping subdomain?  Is this just for something internal or does it affect the semantics of the solver?  And I assume I can still set the overlap and ASM will grow my subdomains accordingly?