On Thu, May 19, 2016 at 7:43 AM, Elias Karabelas < [email protected]> wrote:
> Well I don't bother to much about which PC is use. I just wanted to look > what's possible. One can of course come up with some kind of augmented > Lagrange formulation, but then you end up with a saddle point problem. > We do understand PCs for saddle point problems, but I do not know of anything for A+rank 1, except updated factorizations. Matt > On 19.05.2016 14:41, Matthew Knepley wrote: > > On Thu, May 19, 2016 at 7:39 AM, Elias Karabelas < > <[email protected]>[email protected]> wrote: > >> Ok maybe I should go a little bit more into detail. I have some stokes >> problem in a bifurcating Y-tube. Now I would like to enforce some >> prescribed flux splits at the outlets. After some literature research i >> found a Nitsche method to do that. And if you consider the additional >> billinear forms you end up with some nonlocal coupling terms at the outlets >> (which are those vectors I talked earlier) >> > > Keep the Cc. > > I can see that you might have that formulation, but how you would > incorporate that into AMG, I have no idea. > > Matt > > >> >> On 19.05.2016 14:31, Matthew Knepley wrote: >> >> On Thu, May 19, 2016 at 7:29 AM, Elias Karabelas < >> <[email protected]>[email protected]> wrote: >> >>> maybe something with PCSHELL? >>> >> >> No, I mean that I do not understand what algorithm you might use (apart >> from the implementation). >> >> Matt >> >> >>> >>> On 19.05.2016 14:28, Matthew Knepley wrote: >>> >>> On Thu, May 19, 2016 at 2:48 AM, Elias Karabelas < >>> <[email protected]>[email protected]> 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? >>>> >>> >>> I do not know how you would do that. Its possible other people have >>> ideas. >>> >>> Thanks, >>> >>> Matt >>> >>> >>>> Kind Regards >>>> Elias >>>> >>>> -- >>>> Dr Elias Karabelas >>>> >>>> Medical University of Graz >>>> Institute of Biophysics >>>> Harrachgasse 21/IV >>>> 8010 Graz, Austria >>>> >>>> Phone: +43 316 380 7759 <%2B43%20316%20380%207759> >>>> Email: <[email protected]>[email protected] >>>> Web : <http://forschung.medunigraz.at/fodok/staff?name=EliasKarabelas> >>>> http://forschung.medunigraz.at/fodok/staff?name=EliasKarabelas >>>> >>>> >>> >>> >>> -- >>> What most experimenters take for granted before they begin their >>> experiments is infinitely more interesting than any results to which their >>> experiments lead. >>> -- Norbert Wiener >>> >>> >>> -- >>> Dr Elias Karabelas >>> >>> Medical University of Graz >>> Institute of Biophysics >>> Harrachgasse 21/IV >>> 8010 Graz, Austria >>> >>> Phone: +43 316 380 7759 >>> Email: [email protected] >>> Web : http://forschung.medunigraz.at/fodok/staff?name=EliasKarabelas >>> >>> >> >> >> -- >> What most experimenters take for granted before they begin their >> experiments is infinitely more interesting than any results to which their >> experiments lead. >> -- Norbert Wiener >> >> >> -- >> Dr Elias Karabelas >> >> Medical University of Graz >> Institute of Biophysics >> Harrachgasse 21/IV >> 8010 Graz, Austria >> >> Phone: +43 316 380 7759 >> Email: [email protected] >> Web : http://forschung.medunigraz.at/fodok/staff?name=EliasKarabelas >> >> > > > -- > What most experimenters take for granted before they begin their > experiments is infinitely more interesting than any results to which their > experiments lead. > -- Norbert Wiener > > > -- > Dr Elias Karabelas > > Medical University of Graz > Institute of Biophysics > Harrachgasse 21/IV > 8010 Graz, Austria > > Phone: +43 316 380 7759 > Email: [email protected] > Web : http://forschung.medunigraz.at/fodok/staff?name=EliasKarabelas > > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener
