[petsc-users] FIELDSPLIT fields

[Rossi, Simone]

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
>> 
>