[petsc-users] KSPBuildResidual in ex42.c

[Klaij, Christiaan]

> > In src/ksp/ksp/examples/tutorials/ex42.c.html the Stokes system
> > is solved and KSPBuildResidual is used to compute the residuals
> > for the velocity components and pressure individually. Are these
> > the preconditioned residuals or the true residuals?
>
>
> The true residual.
>
>
> > And how to
> > get both?
> >
>
> Precondition it.
>
> Note that if you only want norms, GMRES will compute one (preconditioned by
> default).

Yes, only the norms. As I understand now, GMRES will compute the
norm of the total system residual [U,V,W,P], but I would like the
norms of [U], [V], [W] and [P] residuals separated. Based on
ex42, I got the impression that I have to use KSPBuildResidual.


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

MARIN
2, Haagsteeg, P.O. Box 28, 6700 AA Wageningen, The Netherlands
T +31 317 49 39 11, F +31 317 49 32 45, I www.marin.nl