[petsc-users] Question about KSP

[Barry Smith]

   Just reuse the old preconditioner. If you keep on making rank one changes then once the preconditioner starts performing poorly "start all over again" by building a new preconditioner from scratch.  Only if this doesn't perform ok for some reason would I try anything more complicated.


   Barry

> On May 19, 2016, at 2:48 AM, Elias Karabelas <elias.karabelas at medunigraz.at> wrote:
> 
> Dear all,
> 
> I have a question about preconditioned solvers. So, I have a Sparsematrix, say A, and now for some reason I would like to add some rank-one term u v^T to that matrix.
> As far as I know about Petsc, I can define the action of this matrix with MatShell. But is it possible to adapt the preconditioner (like a AMG) of my KSP to handle that kind of MatShell?
> 
> Kind Regards
> Elias
> 
> -- 
> Dr Elias Karabelas
> 
> Medical University of Graz
> Institute of Biophysics
> Harrachgasse 21/IV
> 8010 Graz, Austria
> 
> Phone: +43 316 380 7759
> Email: elias.karabelas at medunigraz.at
> Web  : http://forschung.medunigraz.at/fodok/staff?name=EliasKarabelas
>