[petsc-users] difference between left and right pc

[Klaij, Christiaan]

> > I'm solving a system with GMRES using the same preconditioner either on
> > the left or on the right.
> > For left preconditioning I get two orders of reduction for the
> > preconditioned residual in 20 its:
> >
>
> Notice here that your "preconditioner" is far from one. It manages to blow
> up the true residual by
> 5 orders of magnitude, from which it never recovers. The right
> preconditioning just avoids being
> so screwed up.
>
>    Matt

Yes, I noticed that. It does recover 2 orders in 20 its, and it
can recover 5 orders and beyond in a few hundred its. What I
don't understand is how the same preconditioner applied to the
right "just avoids being so screwed up".

Chris


dr. ir. Christiaan Klaij
CFD Researcher
Research & Development
E mailto:C.Klaij at marin.nl
T +31 317 49 33 44

MARIN
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