[petsc-users] Method and PC for indefinite FE-problem

[Jed Brown]

On Wed, May 9, 2012 at 3:57 PM, Mårten Ullberg <martenullberg at gmail.com>wrote:

> it is actually a steady-state solution I'm looking for. Didn't think
> it would be that hard. I'll let you know if find any appropriate
> method to go with my problem.
>

The indefinite Helmholtz problem is notoriously difficult at high
frequency.

http://www.mathe.tu-freiberg.de/~ernst/PubArchive/helmholtzDurham.pdf

For low frequency, many standard methods will work.


>
> One other question, is it big difference between the symmetric QMR
> method from the two other QMR methods implemented in PETSc? I've found
> some references too that method and indefinite problems.
>

Just try it. The QMR algorithms are not equivalent, but they have worked
similarly for some other people solving indefinite problems. If you don't
have an imaginary shift, it would be standard to use MINRES.
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