[petsc-dev] SNES for 2x2 problems

[Matthew Knepley]

On Wed, Jan 2, 2013 at 4:19 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> On Wed, Jan 2, 2013 at 4:16 PM, Matthew Knepley <knepley at gmail.com> wrote:
>
>> On Wed, Jan 2, 2013 at 3:21 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>>
>>> Matt, you know how we always tell people not to use KSP (or even Lapack)
>>> for 2x2 problems? Surely the same advice applies to SNES, but your point
>>> location code is doing it.
>>>
>>
>> Yep. The wrapping overhead is far less with some Newton iterations
>>
>
> Bogus
>
>
>> , and we have no good alternative.
>>
>
> I posit that it's fewer lines of code (and much faster) to just write out
> the Newton iteration on the spot. You don't need the full algorithmic
> infrastructure for point location.
>

And if it does not converge with fixed step? It will eventually morph nto
SNES.

I think your approach is bogus unless you can prove that your simple thing
is sufficient.

   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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