> > 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. > > > > Yes, the cost of building the residual (check -log_summary to see how big > it is) is a reason why people often avoid GMRES if they need the full > residual. It's directly available with GCR, for example (which is otherwise > similar in work to FGMRES) and with most of the non-residual-minimizing > methods.
I find GCR to be less robust than FGMRES, but ok, suppose I switch to GCR, how would I get the residual vector? 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
