On Wed, Mar 16, 2011 at 8:27 AM, Thomas Witkowski < thomas.witkowski at tu-dresden.de> wrote:
> Jed Brown wrote: > > On Wed, Mar 16, 2011 at 07:37, Thomas Witkowski < >> thomas.witkowski at tu-dresden.de <mailto:thomas.witkowski at tu-dresden.de>> >> wrote: >> >> Thanks for explanations! It works fine in my code. But I have two >> questions about it, maybe you can help me with them: >> - To the first, is the LU factorization on block A_00 done only once? >> >> >> Yes, one way to confirm this is to run with -log_summary and check >> MatLUFactor{Sym,Num}. >> >> - I have run the code with -fieldsplit_1_ksp_monitor to get some >> more information about the internal solves. I expected to get >> information about one iterative solver (for solving the Schur >> complement system), but I got three, all of them need around 20 >> iterations for my example. Could you explain to me what is >> actually solved there? >> >> >> I'm going to guess that you still have an outer KSP that (in the global >> norm, rather than the partitioned norm used inside of splits) has a tighter >> tolerance, therefore it takes a few outer iterations. If you use loose inner >> tolerances then the preconditioner becomes nonlinear and you'll need to use >> FGMRES for the outer. When in doubt, run with -ksp_view and show us the >> results if you don't understand. Additionally, monitoring inner solves >> separately can be useful, e.g. -fieldsplit_0_ksp_converged_reason >> -fieldsplit_1_ksp_monitor -ksp_monitor_true_residual. >> > Okay, I run my code with the options "-pc_fieldsplit_type schur > -fieldsplit_interior_ksp_type preonly -fieldsplit_interior_pc_type bjacobi > -fieldsplit_interior_sub_pc_type lu -fieldsplit_boundary_ksp_monitor > -ksp_monitor_true_residual -fieldsplit_interior_ksp_converged_reason". The > splits are named "interior" and "boundary". The ksp output is as follows: > > Linear solve converged due to CONVERGED_ITS iterations 1 > Residual norms for fieldsplit_boundary_ solve. > 0 KSP Residual norm 1.790059331071e-04 > Linear solve converged due to CONVERGED_ITS iterations 1 > 1 KSP Residual norm 1.237356212928e-04 > Linear solve converged due to CONVERGED_ITS iterations 1 > 2 KSP Residual norm 7.952220245101e-05 > Linear solve converged due to CONVERGED_ITS iterations 1 > 3 KSP Residual norm 3.502858665398e-05 > Linear solve converged due to CONVERGED_ITS iterations 1 > 4 KSP Residual norm 1.601085190129e-05 > Linear solve converged due to CONVERGED_ITS iterations 1 > 5 KSP Residual norm 8.491161243057e-06 > Linear solve converged due to CONVERGED_ITS iterations 1 > 6 KSP Residual norm 4.778227395989e-06 > Linear solve converged due to CONVERGED_ITS iterations 1 > 7 KSP Residual norm 2.571919352633e-06 > Linear solve converged due to CONVERGED_ITS iterations 1 > 8 KSP Residual norm 1.353979940120e-06 > Linear solve converged due to CONVERGED_ITS iterations 1 > 9 KSP Residual norm 7.408377337496e-07 > Linear solve converged due to CONVERGED_ITS iterations 1 > 10 KSP Residual norm 3.810694345834e-07 > Linear solve converged due to CONVERGED_ITS iterations 1 > 11 KSP Residual norm 1.955889542056e-07 > Linear solve converged due to CONVERGED_ITS iterations 1 > 12 KSP Residual norm 9.938906113920e-08 > Linear solve converged due to CONVERGED_ITS iterations 1 > 13 KSP Residual norm 4.893445675773e-08 > Linear solve converged due to CONVERGED_ITS iterations 1 > 14 KSP Residual norm 2.395128458062e-08 > Linear solve converged due to CONVERGED_ITS iterations 1 > 15 KSP Residual norm <1.2464425896>1.246442589657e-08 > Linear solve converged due to CONVERGED_ITS iterations 1 > 16 KSP Residual norm 6.316454504022e-09 > Linear solve converged due to CONVERGED_ITS iterations 1 > 17 KSP Residual norm 3.088668836241e-09 > Linear solve converged due to CONVERGED_ITS iterations 1 > 18 KSP Residual norm 1.593454221996e-09 > Linear solve converged due to CONVERGED_ITS iterations 1 > [0] Petsc-Iteration 0: 0.574504 > 0 KSP preconditioned resid norm 5.745043818120e-01 true resid norm > 1.584249437360e-01 ||r(i)||/||b|| 1.000000000000e+00 > Linear solve converged due to CONVERGED_ITS iterations 1 > Residual norms for fieldsplit_boundary_ solve. > 0 KSP Residual norm 1.790059331000e-04 > Linear solve converged due to CONVERGED_ITS iterations 1 > 1 KSP Residual norm 1.237356237744e-04 > Linear solve converged due to CONVERGED_ITS iterations 1 > 2 KSP Residual norm 7.952220078415e-05 > Linear solve converged due to CONVERGED_ITS iterations 1 > 3 KSP Residual norm 3.502859285561e-05 > Linear solve converged due to CONVERGED_ITS iterations 1 > 4 KSP Residual norm 1.601086485810e-05 > Linear solve converged due to CONVERGED_ITS iterations 1 > 5 KSP Residual norm 8.491169384185e-06 > Linear solve converged due to CONVERGED_ITS iterations 1 > 6 KSP Residual norm 4.778229157872e-06 > Linear solve converged due to CONVERGED_ITS iterations 1 > 7 KSP Residual norm 2.571917112191e-06 > Linear solve converged due to CONVERGED_ITS iterations 1 > 8 KSP Residual norm 1.353977280183e-06 > Linear solve converged due to CONVERGED_ITS iterations 1 > 9 KSP Residual norm 7.408352317360e-07 > Linear solve converged due to CONVERGED_ITS iterations 1 > 10 KSP Residual norm 3.810710583336e-07 > Linear solve converged due to CONVERGED_ITS iterations 1 > 11 KSP Residual norm 1.955898169394e-07 > Linear solve converged due to CONVERGED_ITS iterations 1 > 12 KSP Residual norm 9.938892788465e-08 > Linear solve converged due to CONVERGED_ITS iterations 1 > 13 KSP Residual norm 4.893428546840e-08 > Linear solve converged due to CONVERGED_ITS iterations 1 > 14 KSP Residual norm 2.395120857135e-08 > Linear solve converged due to CONVERGED_ITS iterations 1 > 15 KSP Residual norm <1.2464367927>1.246436792784e-08 > Linear solve converged due to CONVERGED_ITS iterations 1 > 16 KSP Residual norm 6.316409779118e-09 > Linear solve converged due to CONVERGED_ITS iterations 1 > 17 KSP Residual norm 3.088649355374e-09 > Linear solve converged due to CONVERGED_ITS iterations 1 > 18 KSP Residual norm 1.593449602302e-09 > Linear solve converged due to CONVERGED_ITS iterations 1 > Linear solve converged due to CONVERGED_ITS iterations 1 > Residual norms for fieldsplit_boundary_ solve. > 0 KSP Residual norm 1.593449603155e-09 > Linear solve converged due to CONVERGED_ITS iterations 1 > 1 KSP Residual norm 1.011857676662e-09 > Linear solve converged due to CONVERGED_ITS iterations 1 > 2 KSP Residual norm 5.660892669788e-10 > Linear solve converged due to CONVERGED_ITS iterations 1 > 3 KSP Residual norm 3.046799343903e-10 > Linear solve converged due to CONVERGED_ITS iterations 1 > 4 KSP Residual norm <1.6004713993>1.600471399329e-10 > Linear solve converged due to CONVERGED_ITS iterations 1 > 5 KSP Residual norm 8.083216601016e-11 > Linear solve converged due to CONVERGED_ITS iterations 1 > 6 KSP Residual norm 4.308671648345e-11 > Linear solve converged due to CONVERGED_ITS iterations 1 > 7 KSP Residual norm 2.381959817139e-11 > Linear solve converged due to CONVERGED_ITS iterations 1 > 8 KSP Residual norm 1.264839790114e-11 > Linear solve converged due to CONVERGED_ITS iterations 1 > 9 KSP Residual norm 6.435098853282e-12 > Linear solve converged due to CONVERGED_ITS iterations 1 > 10 KSP Residual norm 3.184769579797e-12 > Linear solve converged due to CONVERGED_ITS iterations 1 > 11 KSP Residual norm <1.5022019430>1.502201943016e-12 > Linear solve converged due to CONVERGED_ITS iterations 1 > 12 KSP Residual norm 7.099486208425e-13 > Linear solve converged due to CONVERGED_ITS iterations 1 > 13 KSP Residual norm 3.443222176388e-13 > Linear solve converged due to CONVERGED_ITS iterations 1 > 14 KSP Residual norm <1.6478434989>1.647843498912e-13 > Linear solve converged due to CONVERGED_ITS iterations 1 > 15 KSP Residual norm 8.208508173926e-14 > Linear solve converged due to CONVERGED_ITS iterations 1 > 16 KSP Residual norm 4.376604355287e-14 > Linear solve converged due to CONVERGED_ITS iterations 1 > 17 KSP Residual norm 2.596069152755e-14 > Linear solve converged due to CONVERGED_ITS iterations 1 > 18 KSP Residual norm 1.335744434252e-14 > Linear solve converged due to CONVERGED_ITS iterations 1 > 1 KSP preconditioned resid norm 2.608069232839e-13 true resid norm > 1.449869994655e-13 ||r(i)||/||b|| 9.151778504469e-13 > > I have no idea how to interpret this output! Could you help me with it? Get rid of -fieldsplit_interior_ksp_converged_reason. It is confusing things. Then you will see the outer iteration and the inner boundary iteration which is indented. Matt > > Thomas > -- 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-dev/attachments/20110316/ddaf834c/attachment.html>
