22 May
2012
22 May
'12
10:04 a.m.
On Tue, May 22, 2012 at 9:54 AM, Klaij, Christiaan <[email protected]> wrote:
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.