[petsc-users] Clarification on PCASMSetLocalSubdomain is and is_local

[Luc Berger-Vergiat]

Ok I get it,  then if I have multiple subdomains on the local processor 
is and is_local will be arrays of is that represent each subdomain on 
that processor?

Best,
Luc

On 06/02/2016 06:21 PM, Matthew Knepley wrote:
> On Thu, Jun 2, 2016 at 5:11 PM, Luc Berger-Vergiat 
> <lb2653 at columbia.edu <mailto:lb2653 at columbia.edu>> wrote:
>
>     Hi all,
>     I would like a quick clarification on what is and is_local are
>     representing in the PCASMSetLocalSubdomains().
>     My understanding is that if I have two mpi ranks and four
>     subdomains I can end up having four blocks that I can denote as
>     follows:
>
>                |   domain1  |  domain2  |  domain3  | domain3   |
>     rank1  |    block11  |    block12  |   block13   | |
>     rank2  |    block21  |    block22  |       --         | block24 |
>
>     to each blockIJ I associate isIJ.
>
>     So for rank1 I will have is=[1,2,3] and is_local=[is11,is12,is13],
>     and for rank2 I will have is=[1,2,4] and is_local=[is21,is22,is24].
>     Or am I not understanding things correctly?
>
>
> I did not understand the above.
>
> The best way to think of this is algebraically. Suppose you have a 
> matrix A, and you divide the rows into k disjoint sets where each
> process gets one set. Then is_local on each process is a list of the 
> rows in that set. Now we also allow some overlap, which means
> rows in other sets are also used. The is on each process contains both 
> is_local and these extra rows from other sets.
>
>   Thanks,
>
>      Matt
>
>
>     -- 
>     Best,
>     Luc
>
>
>
>
>
> -- 
> What most experimenters take for granted before they begin their 
> experiments is infinitely more interesting than any results to which 
> their experiments lead.
> -- Norbert Wiener

-- 
Best,
Luc

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20160602/09d7de8f/attachment.html>