[petsc-users] gamg and zero pivots

[Gideon Simpson]

Thanks for the suggestions guys.  Barry’s field split approach gives sensible behavior.  Now I’m working on tuning it.
-gideon

> On Sep 21, 2015, at 9:21 AM, Jed Brown <jed at jedbrown.org> wrote:
> 
> Matthew Knepley <knepley at gmail.com> writes:
>>> At the same time, the first block, as discussed, has
>>> these zeros on the diagonal, and can’t use SOR.
>>> 
>> 
>> Chebyshev/Jacobi is the obvious next try.
> 
> Not really; the Chebyshev polynomial exceeds 1 left of the origin, so
> it's pretty non-functional on indefinite operators.  Pretending like
> Gideon's saddle point problem is positive definite is not a solution.

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