Use -ksp_view to confirm the options are actually set. Fande
Sent from my iPhone > On Oct 16, 2018, at 7:40 PM, Ellen M. Price <[email protected]> > wrote: > > Maybe a stupid suggestion, but sometimes I forget to call the > *SetFromOptions function on my object, and then get confused when > changing the options has no effect. Just a thought from a fellow grad > student. > > Ellen > > >> On 10/16/2018 09:36 PM, Matthew Knepley wrote: >> On Tue, Oct 16, 2018 at 9:14 PM Weizhuo Wang <[email protected] >> <mailto:[email protected]>> wrote: >> >> I just tried both, neither of them make a difference. I got exactly >> the same curve with either combination. >> >> >> I have a hard time believing you. If you make the residual tolerance >> much finer, your error will definitely change. >> I run tests every day that do exactly this. You can run them too, since >> they are just examples. >> >> Thanks, >> >> Matt >> >> >> Thanks! >> >> Wang weizhuo >> >> On Tue, Oct 16, 2018 at 8:06 PM Matthew Knepley <[email protected] >> <mailto:[email protected]>> wrote: >> >> On Tue, Oct 16, 2018 at 7:26 PM Weizhuo Wang >> <[email protected] <mailto:[email protected]>> wrote: >> >> Hello again! >> >> After some tweaking the code is giving right answers now. >> However it start to disagree with MATLAB results >> ('traditional' way using matrix inverse) when the grid is >> larger than 100*100. My PhD advisor and I suspects that the >> default dimension of the Krylov subspace is 100 in the test >> case we are running. If so, is there a way to increase the >> size of the subspace? >> >> >> 1) The default subspace size is 30, not 100. You can increase >> the subspace size using >> >> -ksp_gmres_restart n >> >> 2) The problem is likely your tolerance. The default solver >> tolerance is 1e-5. You can change it using >> >> -ksp_rtol 1e-9 >> >> Thanks, >> >> Matt >> >> >> >> Disagrees.png >> >> Thanks! >> >> Wang Weizhuo >> >> On Tue, Oct 9, 2018 at 2:50 AM Mark Adams <[email protected] >> <mailto:[email protected]>> wrote: >> >> To reiterate what Matt is saying, you seem to have the >> exact solution on a 10x10 grid. That makes no sense >> unless the solution can be represented exactly by your >> FE space (eg, u(x,y) = x + y). >> >> On Mon, Oct 8, 2018 at 9:33 PM Matthew Knepley >> <[email protected] <mailto:[email protected]>> wrote: >> >> On Mon, Oct 8, 2018 at 9:28 PM Weizhuo Wang >> <[email protected] >> <mailto:[email protected]>> wrote: >> >> The code is attached in case anyone wants to >> take a look, I will try the high frequency >> scenario later. >> >> >> That is not the error. It is superconvergence at the >> vertices. The real solution is trigonometric, so your >> linear interpolants or whatever you use is not going >> to get the right value in between mesh points. You >> need to do a real integral over the whole interval >> to get the L_2 error. >> >> Thanks, >> >> Matt >> >> >> On Mon, Oct 8, 2018 at 7:58 PM Mark Adams >> <[email protected] <mailto:[email protected]>> wrote: >> >> >> >> On Mon, Oct 8, 2018 at 6:58 PM Weizhuo Wang >> <[email protected] >> <mailto:[email protected]>> wrote: >> >> The first plot is the norm with the flag >> -pc_type lu with respect to number of >> grids in one axis (n), and the second >> plot is the norm without the flag >> -pc_type lu. >> >> >> So you are using the default PC w/o LU. The >> default is ILU. This will reduce high >> frequency effectively but is not effective >> on the low frequency error. Don't expect >> your algebraic error reduction to be at the >> same scale as the residual reduction (what >> KSP measures). >> >> >> >> >> -- >> Wang Weizhuo >> >> >> >> -- >> 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 >> >> https://www.cse.buffalo.edu/~knepley/ >> >> <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.cse.buffalo.edu_-7Eknepley_&d=DwMFaQ&c=OCIEmEwdEq_aNlsP4fF3gFqSN-E3mlr2t9JcDdfOZag&r=hsLktHsuxNfF6zyuWGCN8x-6ghPYxhx4cV62Hya47oo&m=EFM29ATgv4U8PjXEtfgMkuxKr5DGscMlH-j769W5W_4&s=grgSL2LaDCthvYvvFITmeOOWPCwgmNfYRPs94N8kmOs&e=> >> >> >> >> -- >> Wang Weizhuo >> >> >> >> -- >> 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 >> >> https://www.cse.buffalo.edu/~knepley/ >> <http://www.cse.buffalo.edu/%7Eknepley/> >> >> >> >> -- >> Wang Weizhuo >> >> >> >> -- >> 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 >> >> https://www.cse.buffalo.edu/~knepley/ >> <http://www.cse.buffalo.edu/%7Eknepley/>
