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
