[petsc-users] Recursive field split with MatNest

[Colin McAuliffe]

A few other questions on this: since each field has a name, can this be
used as an identifier for the ISes instead of the hash? I'm brushing up on
hashes but also trying to think of simpler alternatives that work.

Next, since MatNestFindSubMat returns a Mat and not a list of Mats, will it
be necessary to create a mat nest for the case of a submatrix that is made
up of several other submatrices?

Thanks,
Colin

On Mon, Jan 12, 2015 at 9:39 PM, Colin McAuliffe <cjm2176 at columbia.edu>
wrote:

> Thanks for the comments Jed and Matt, I'll defer to your judgement
> regarding the implementation that is the least intrusive. I'll take a look
> at this later on when I have time.
> Colin
>
> On Mon, Jan 12, 2015 at 12:29 PM, Jed Brown <jed at jedbrown.org> wrote:
>
>> Matthew Knepley <knepley at gmail.com> writes:
>> > I don't like this business of ISes holding pointers to other ISes. This
>> > fundamentally
>> > changes the model. The hashing sounds workable.
>>
>> ISs are immutable and a reference would probably be held anyway, so I
>> don't think it's evil.
>>
>> We also have to think about recursive composition and I'd rather not
>> have to walk a subset DAG.  If we hash, the IS would just store a list
>> of "known subset hashes" with the semantic
>>
>>   (A ∪ B).known_subset_hashes =
>>       A.known_subset_hashes ∪ B.known_subset_hashes ∪ [hash(A)] ∪
>> [hash(B)]
>>
>
>
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