[petsc-users] Recursive field split with MatNest

[Matthew Knepley]

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
fundamentally
changes the model. The hashing sounds workable.

  Matt

-- 
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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