Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

At the moment I could solve it by implementing an adaptive step size, from 0.1 to 0.25 to 0.5, then the problem does not arise and the solution converges fast enough. Still I noted that when using other values for the maximal and minimal grid density I again get the problem with the non-converg

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

If I understand you correctly: I should either recheck my matrix assembly, or test a smaller step when my solution stalls, even though that goes against my understanding of the Newton method (step size increases)? I noted that (when stalling) my residual value was approximately half the l2-norm

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

Step-15 uses a fixed alpha = 0.1, but in the suggestions it is proposed to increase alpha to 1, when suitable in order to increase convergence. I am also using a fixed alpha of 0.1 at the moment, thus it will never go to zero. Am Freitag, 6. Oktober 2017 15:27:40 UTC+2 schrieb Wolfgang Bangerth

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

On 10/06/2017 07:20 AM, 'Maxi Miller' via deal.II User Group wrote: Isn't that basically the method done in step-15 and step-33 (line search)? But why should my step length (I assume it is alpha) go to zero? Or is it the newton-update (which also should go to zero, when being close to the soluti

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

Isn't that basically the method done in step-15 and step-33 (line search)? But why should my step length (I assume it is alpha) go to zero? Or is it the newton-update (which also should go to zero, when being close to the solution)? Am Freitag, 6. Oktober 2017 15:13:08 UTC+2 schrieb Wolfgang Ba

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

Currentl2 norm is0.003245 Residual:0.001620 Currentl2 norm is0.003245 Residual:0.001620 | with the l2-norm as the l2-norm of the RHS, and the residual calculated as shown above. Do you do a line search? Is your step length going to zero? Best W. -- ---

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

Short update: Changing the threshold from 1e-6 to 1e-8 did not change anything, it still loops at the same values as final values. Am Freitag, 6. Oktober 2017 11:56:59 UTC+2 schrieb Maxi Miller: > > Concerning the first point: > Currently I am controlling the solver as in > SolverControl

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

Concerning the first point: Currently I am controlling the solver as in SolverControl solver_control (dof_handler.n_dofs(), (system_rhs.l2_norm() > 0) ? 1e-6 * system_rhs.l2_norm() : 1e-6); Is your suggestion to decrease that threshold? Concerning the

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

Unfortunately that was not the reason for my problem (even though it was a nice addition). My current program output is Refined mesh 23 Refining mesh Adding boundary conditions Calculating initial residual Initial Residual: 0.001626 Current l2 norm is 0.003256 Residual: 0.

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

I’m a bit confused by what you are asking. The entries in the residual vector corresponding to constrained dofs will converge to a non-zero number. Those corresponding to unconstrained dofs should converge to zero. As is stated in step-15 … we have to set to zero the elements of the residual ve

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

Compared to the target value? Depending on the values between ~1e-6 and 2e-3, but it can be larger, too. I will check the latter function and compare it to the current solution, but I thought by using ZeroFunction as boundary condition that then all boundary_dofs are set to zero. Am Donnerstag,

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

> Isn't the 'distribute'-line doing exactly that? Or is that a mistake? No, set_zero() will set the entries to zero, distribute() will set them to their correct nonzero entry. Also, how small are the errors that you are getting when it levels off? -- Timo Heister http://www.math.clemson.edu/~he

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

Isn't the 'distribute'-line doing exactly that? Or is that a mistake? Am Donnerstag, 5. Oktober 2017 18:24:58 UTC+2 schrieb mac: > > I’m referring specifically to a line similar to the following where all > entries in the residual associated with constrained dofs are zeroed: > > for (unsigned int

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

I’m referring specifically to a line similar to the following where all entries in the residual associated with constrained dofs are zeroed: for (unsigned int i=0; ihttp://www.dealii.org/developer/doxygen/deal.II/classDoFHandler.html#a54e7270f2ba6206604f794114b39a2aa>(); ++i) if (boundary_dofs

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

I assume so. My approach to ensure that is: I create a ConstraintMatrix called "Newton_constraints", initialize it as following: newton_constraints.clear(); newton_constraints.reinit(solution_relevant_partitioning); DoFTools::make_hanging_node_constraints(dof_handler, newton_constraints); VectorT

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

Are you ensuring that the entries in F(U) associated with the constrained dofs are set to zero? As shown in http://www.dealii.org/developer/doxygen/deal.II/step_15.html#MinimalSurfaceProblemcompute_residual

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

Yes, I forgot to clarify. I am calculating the l2-norm of the right hand side, i.e. which contains F(U) (when staying in the terminology of step-15). According to my knowledge that should go to zero, after that is the whole goal of the Newton iteration (if my understanding of the method is corr

Re: [deal.II] L2-norm gets decreased to certain value, but stays above threshold

On 10/05/2017 08:52 AM, 'Maxi Miller' via deal.II User Group wrote: Having a nonlinear, time-dependent heat equation, I tried to implement it as in step-15 and in step-33. Everytime my l2-value goes below a certain threshold, The l2 norm of what? The solution? The residual? I make one step i

[deal.II] L2-norm gets decreased to certain value, but stays above threshold

Having a nonlinear, time-dependent heat equation, I tried to implement it as in step-15 and in step-33. Everytime my l2-value goes below a certain threshold, I make one step in time (or I refine the mesh). At the beginning the L2-value goes down rather fast, but later it slows down, and even sto