[petsc-users] Recursive field split with MatNest

[Jed Brown]

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)]
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 818 bytes
Desc: not available
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20150112/2fc32119/attachment-0001.pgp>