[petsc-users] FIELDSPLIT fields

[Smith, Barry F.]

  2 should belong to one of the subdomains, either one is fine.

   Barry


> On Sep 5, 2018, at 10:46 AM, Rossi, Simone <srossi at email.unc.edu> wrote:
> 
> I’m trying to setup GASM, but I’m probably misunderstanding something.
> 
> If I have this mesh
> 
> 0 —— 1 —— 2 —— 3 —— 4
> subdomain 1  |   subdomain 2
> 
> I create an interior (no overlap) and an outer (with overlap) IS for both subdomains.
> 
> In my naive understanding
> 
> iis1  = {0, 1}
> ois1 = {0, 1, 2}
> 
> and
> 
> iis2  = {3, 4}
> ois2 = {2, 3, 4}
> 
> but then the node at the interface (node 2) does not belong to any interior IS. Should node 2 belong to both interior IS? Or should it belong only to one of the domains?
> 
> Thanks,
> Simone
> 
> 
> On Aug 15, 2018, at 22:11, Griffith, Boyce Eugene <boyceg at email.unc.edu> wrote:
> 
>> 
>> 
>>> On Aug 15, 2018, at 10:07 PM, Smith, Barry F. <bsmith at mcs.anl.gov> wrote:
>>> 
>>> 
>>> Yes you can have "overlapping fields" with FIELDSPLIT but I don't think you can use FIELDSPLIT for your case. You seem to have a geometric decomposition into regions. ASM and GASM are intended for such decompositions. Fieldsplit is for multiple fields that each live across the entire domain.
>> 
>> Basically there is one field the lives on the entire domain, and another field that lives only on a subdomain.
>> 
>> Perhaps we could do GASM for the geometric split and FIELDSPLIT within the subdomain with the two fields.
>> 
>>> Barry
>>> 
>>> 
>>>> On Aug 15, 2018, at 7:42 PM, Griffith, Boyce Eugene <boyceg at email.unc.edu> wrote:
>>>> 
>>>> Is it permissible to have overlapping fields in FIELDSPLIT? We are specifically thinking about how to handle DOFs living on the interface between two regions.
>>>> 
>>>> Thanks!
>>>> 
>>>> — Boyce
>>> 
>> 
>