Hi, My problem converges using:
-pre -snes_type ls -snes_type basic but I still get divergence if I add to the above options the direct linear solver: -ksp_type preonly -pc_type lu This looks suspicious to me, also because I get divergence if I delete the "-pre" option (also with iterative linear solver)... Best, Lorenzo On Mar 6, 2013, at 7:32 PM, Subramanya Gautam Sadasiva wrote: > I have noticed that the default line search type used by petsc fails quite > regularly (at least for the problem that I am solving) . I would suggest > doing "-snes_linesearch_type basic" . This works for the latest version of > petsc. I think this option used to be "-snes_ls_type" for the older versions > of petsc. > > > Subramanya Sadasiva > > "But memory eventually fades. Turbulences damp out, internal strains yield to > plastic flow, concentration inhomogeneities diffuse to uniformity. Systems > tend to subside to very simple states,independent of their specific history." > Herbert Callen . Thermodynamics and an Introduction to Thermostatics. > > ----- Original Message ----- > From: "Lorenzo Zanon" <[email protected]> > To: "Derek Gaston" <[email protected]> > Cc: "Subramanya Gautam Sadasiva" <[email protected]>, "libmesh-users" > <[email protected]> > Sent: Wednesday, March 6, 2013 1:26:21 PM > Subject: Re: [Libmesh-users] Newton iteration > > I get convergence only using the preconditioning option "-pre". If I set a > direct solver for the linear system - as I usually do - with the option > "-ksp_type preonly -pc_type lu", I get instead a failure message: > > Nonlinear solve did not converge due to DIVERGED_LS_FAILURE > > I think there's still a problem, because I should get convergence also with > the linear solver, if the problem is properly set. Or am I wrong? > > Thanks a lot, > Lorenzo > > On Mar 6, 2013, at 4:48 PM, Derek Gaston wrote: > >> I would also recommend using -ksp_monitor so you can see how the linear >> solve is going. I suspect that it's going nowhere and therefore the solve >> is failing... >> >> Derek >> >> >> On Wed, Mar 6, 2013 at 7:11 AM, Subramanya Gautam Sadasiva >> <[email protected]> wrote: >> Hi, >> If you are using petsc, I'd suggest running with -snes_converged_reason. It >> looks to me that your problem is diverging for some reason. The reasons >> could be that the line-search or the solver is failing , which can also be >> changed with command line options. >> >> Subramanya Sadasiva >> >> "But memory eventually fades. Turbulences damp out, internal strains yield >> to plastic flow, concentration inhomogeneities diffuse to uniformity. >> Systems tend to subside to very simple states,independent of their specific >> history." >> Herbert Callen . Thermodynamics and an Introduction to Thermostatics. >> >> ----- Original Message ----- >> From: "Lorenzo Zanon" <[email protected]> >> To: [email protected] >> Sent: Wednesday, March 6, 2013 6:53:02 AM >> Subject: [Libmesh-users] Newton iteration >> >> Hello, >> >> I'm modifying miscellaneous_ex3.C (2D Laplace-Young Problem Using Nonlinear >> Solvers, in my current libmesh version). After adapting residual and >> jacobian to my own problem, although the tolerance is not met, the Newton >> solver stops after one iteration with an all-zero (incorrect) solution: >> >> NL step 0, |residual|_2 = 1.598435e+00 >> Laplace-Young system solved at nonlinear iteration 0 , final nonlinear >> residual norm: 1.598435e+00 >> >> What could be the reason for that? >> >> Thanks a lot, >> Lorenzo >> >> ------------------------------------------------------------------------------ >> Symantec Endpoint Protection 12 positioned as A LEADER in The Forrester >> Wave(TM): Endpoint Security, Q1 2013 and "remains a good choice" in the >> endpoint security space. For insight on selecting the right partner to >> tackle endpoint security challenges, access the full report. >> http://p.sf.net/sfu/symantec-dev2dev >> _______________________________________________ >> Libmesh-users mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/libmesh-users >> >> ------------------------------------------------------------------------------ >> Symantec Endpoint Protection 12 positioned as A LEADER in The Forrester >> Wave(TM): Endpoint Security, Q1 2013 and "remains a good choice" in the >> endpoint security space. For insight on selecting the right partner to >> tackle endpoint security challenges, access the full report. >> http://p.sf.net/sfu/symantec-dev2dev >> _______________________________________________ >> Libmesh-users mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/libmesh-users >> > ------------------------------------------------------------------------------ Symantec Endpoint Protection 12 positioned as A LEADER in The Forrester Wave(TM): Endpoint Security, Q1 2013 and "remains a good choice" in the endpoint security space. For insight on selecting the right partner to tackle endpoint security challenges, access the full report. http://p.sf.net/sfu/symantec-dev2dev _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
