I see. Thanks, Matt. Yan
On Tue, Apr 5, 2011 at 11:27 PM, Matthew Knepley <knepley at gmail.com> wrote: > On Tue, Apr 5, 2011 at 10:20 PM, Ryan Yan <vyan2000 at gmail.com> wrote: > >> One more ask, :-) >> >> Which one is more efficient, richardson, preonly or no difference, if I am >> going to use direct solver for many times steps. >> > > There should be no difference since direct solves take so long. > > Matt > > >> Thanks, >> >> Yan >> >> On Tue, Apr 5, 2011 at 11:06 PM, Barry Smith <bsmith at mcs.anl.gov> wrote: >> >>> >>> On Apr 5, 2011, at 9:52 PM, Ryan Yan wrote: >>> >>> > Hi, >>> > I am wondering is there a way of checking the residual of a direct >>> solver. It should >>> > be one shot and very small. I tried -ksp_monitor_true_residual, but no >>> thing shows up. I guess a piece of code >>> > $Ax-b$ will do the trick? >>> >>> The reason that the monitor doesn't display anything is not the direct >>> solver but because you are using LU with KSPType of KSPPREONLY if you run >>> with -ksp_type richardson or -ksp_type gmres then -ksp_monitor_true_residual >>> will print the residual as you want. >>> >>> Barry >>> >>> > >>> > Thanks, >>> > >>> > Yan >>> >>> >> > > > -- > 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 > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20110405/90031d2e/attachment-0001.htm>
