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/20110405/8fabf337/attachment.htm>
