From: Lorenzo Zanon <zanon@ai...>  20131209 18:32:07

Hello, I'm sorry it took so long. There were actually a couple of mistakes in my jacobian and residual. Now for the small problem without specifying any options I get: > Running ./exampleopt > > Mesh Information: > mesh_dimension()=3 > spatial_dimension()=3 > n_nodes()=66 > n_local_nodes()=66 > n_elem()=20 > n_local_elem()=20 > n_active_elem()=20 > n_subdomains()=1 > n_partitions()=1 > n_processors()=1 > n_threads()=1 > processor_id()=0 > > EquationSystems > n_systems()=1 > System #0, "StVen" > Type "NonlinearImplicit" > Variables={ "u" "v" "z" } > Finite Element Types="LAGRANGE" > Approximation Orders="FIRST" > n_dofs()=198 > n_local_dofs()=198 > n_constrained_dofs()=18 > n_local_constrained_dofs()=18 > n_vectors()=1 > n_matrices()=1 > DofMap Sparsity > Average OnProcessor Bandwidth <= 39.4545 > Average OffProcessor Bandwidth <= 0 > Maximum OnProcessor Bandwidth <= 54 > Maximum OffProcessor Bandwidth <= 0 > DofMap Constraints > Number of DoF Constraints = 18 > Average DoF Constraint Length= 0 > > NL step 0, residual_2 = 3.464102e05 > NL step 1, residual_2 = 3.126867e05 > NL step 2, residual_2 = 2.835742e05 > NL step 3, residual_2 = 2.579682e05 > NL step 4, residual_2 = 2.351091e05 > NL step 5, residual_2 = 2.144758e05 > NL step 6, residual_2 = 1.957083e05 > NL step 7, residual_2 = 1.785531e05 > NL step 8, residual_2 = 1.628262e05 > NL step 9, residual_2 = 1.463259e05 > NL step 10, residual_2 = 1.280174e05 > NL step 11, residual_2 = 1.073276e05 > NL step 12, residual_2 = 8.355152e06 > NL step 13, residual_2 = 7.606801e06 > NL step 14, residual_2 = 9.503420e11 > NL step 15, residual_2 = 2.354762e15 > StVen system solved at nonlinear iteration 15 , final nonlinear residual norm: 2.354762e15 I get faster convergence with e.g. snes_linesearch_type basic ksp_rtol 1e4: > NL step 0, residual_2 = 3.464102e05 > NL step 1, residual_2 = 2.417540e04 > NL step 2, residual_2 = 6.174706e08 > NL step 3, residual_2 = 3.577768e12 > NL step 4, residual_2 = 7.687278e17 > StVen system solved at nonlinear iteration 4 , final nonlinear residual norm: 7.687278e17 I think it would be fine to use these last options also on a finer mesh then. It finally looks like I don't need JFNK. Thanks! Lorenzo On Nov 26, 2013, at 8:42 PM, Derek Gaston wrote: > On Tue, Nov 26, 2013 at 11:59 AM, Dmitry Karpeyev <karpeev@...> wrote: > LU, naturally, should do better, and we should at least see quicker linear convergence. > If not, it's an indication that your problem is singular. > > LU should only take 1 (ish) linear iteration. > > However, I still suspect that the issue here is that his Jacobian is wrong... which accounts for the degraded nonlinear convergence. > > Lorenzo: Have you double checked your Jacobian statements? Have you checked them against your friend doing FEAP? Your statements should look very similar to theirs... > > Derek 