[petsc-users] Recursive field split with MatNest

Matthew Knepley knepley at gmail.com
Mon Jan 12 11:18:58 CST 2015

On Mon, Jan 12, 2015 at 11:15 AM, Jed Brown <jed at jedbrown.org> wrote:

> Colin McAuliffe <cjm2176 at columbia.edu> writes:
> > I'd be interested in implementing this, I think I should have some time
> to
> > spend on it in a few weeks. I suppose the ISSubset function should
> > determine which ISs were used to make up a third IS? Can this be done by
> > having ISSum attach a list of pointers to the constituent ISs to the
> summed
> > IS for retrieval by ISSubset?
> It could and that would probably be fairly harmless in terms of peak
> memory usage.  An alternative would be to compute a cryptographic hash
> of the index sets and only store that.  This would allow comparison
> without needing to flatten the index sets to arrays of integers (see
> current implementation of ISEqual).

I don't like this business of ISes holding pointers to other ISes. This
changes the model. The hashing sounds workable.


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
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