[CIG-SHORT] PyLith Convergence issue - DIVERGED_FUNCTION_COUNT and CONVERGED_SNORM_RELATIVE
Brad Aagaard
baagaard at usgs.gov
Thu Jun 22 14:28:21 PDT 2017
Josimar,
Please send the pylith_parameters.json file that PyLith generates.
Thanks,
Brad
On 06/22/2017 02:19 PM, Josimar Alves da Silva wrote:
> Matt,
>
> Thanks for the help. Here is the log file with more information:
> https://www.dropbox.com/s/qnpk055o9xg38j1/log.out?dl=0
>
> Let me know if you need anything else.
>
> thank you,
> Josimar
>
> On Thu, Jun 22, 2017 at 3:21 PM, Matthew Knepley <knepley at rice.edu
> <mailto:knepley at rice.edu>> wrote:
>
> On Thu, Jun 22, 2017 at 12:10 PM, Josimar Alves da Silva
> <jsilva.mit at gmail.com <mailto:jsilva.mit at gmail.com>> wrote:
>
> Matt,
>
> Thank you so much for the help. I followed up on your suggestions:
>
> 1) Using snes_max_funcs=10000 did not help. The simulation does
> not go beyond iteration #5000. It stopped at the same time step
> as the previous one.
>
>
> Note this has to be in the [petsc] section. Please add snes_view.
> Then we can see exactly what the setting were.
> It would also be good to add snes_converged_reason
>
> I looked at the log. It makes as much as progress as it will ever
> make after 2 iterates, thus I think there
> is a problem with interplay of tolerances here.
>
> 2) Can you comment a little bit on how can I improve my initial
> guess, as you mentioned here : "if your initial guess is not
> good enough they can fail". What you mean about it ?
>
>
> I mean if you are taking time steps so big that the last solution is
> not close to the next one, the solves will be harder.
>
> Matt
>
> The log file is attached.
>
> thank you so much in advance,
> Josimar
>
>
>
>
> On Thu, Jun 22, 2017 at 11:33 AM, Matthew Knepley
> <knepley at rice.edu <mailto:knepley at rice.edu>> wrote:
>
> On Wed, Jun 21, 2017 at 6:25 PM, Josimar Alves da Silva
> <jsilva.mit at gmail.com <mailto:jsilva.mit at gmail.com>> wrote:
>
> Dear Brad, Matt and Charles,
>
> I am working on a 2-D quasi-static, elastic, simulation
> using rate and state friction model.
>
> The simulation runs fine for many time steps, then at
> some point I get the error below related to
> DIVERGED_FUNCTION_COUNT.
>
> Nonlinear solve did not converge due to
> DIVERGED_FUNCTION_COUNT iterations 5000
>
> All the log files, along with the .cfg files, model
> geometry and boundary conditions as well as a
> convergence plot for the SNES residual can be found on
> the attached .zip file.
>
> I have some questions that I would like to have your input:
>
> 1) Is it possible to extend the maximum value for
> DIVERGED_FUNCTION_COUNT ? Note that I have snes_max_it
> =10000 but SNES still stops at 5000 value.
>
>
> snes_max_funcs 10000
>
> 2) Looking at the convergence plots that I have
> attached, I noticed that the time step that fails
> contains iterations that actually increase the
> residual,instead of decreasing it. Would you know what
> is causing this behavior ?
>
>
> There is no guarantee of decrease with a general nonlinear
> problem.
>
> 3) There are several time steps that converge with
> tolerances smaller than what I ask for using the
> snes_atol (see figure attached). At these time steps I
> get the following
>
> Line search: Aborted due to ynorm < stol*xnorm
> (9.933794721748e-10 < 1.046238089915e-09) and inadequate
> full step.
>
> Nonlinear solve converged due to
> CONVERGED_SNORM_RELATIVE iterations 694
>
>
> This means that even a very short step length gave no
> residual decrease, also known as "stagnation". Here is the
> nonlinear
> solver is just not working.
>
> We have no convergence theory for the friction problems, and
> if your initial guess is not good enough they can fail. We
> want to explore
> more powerful solvers for these, but after we get a revised
> formulation in place.
>
> Thanks,
>
> Matt
>
> Note that I am using snes_error_if_not_converged =true.
>
> Could you please comment on why this is happening and
> how I would fix this issue ? Does it affect the next
> time steps after it ?
>
> Let me know if you need any further information.
>
> Thank you so much for you help in advance,
> Best
> Josimar
>
>
>
> _______________________________________________
> CIG-SHORT mailing list
> CIG-SHORT at geodynamics.org <mailto:CIG-SHORT at geodynamics.org>
> http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short
> <http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short>
>
>
>
> _______________________________________________
> CIG-SHORT mailing list
> CIG-SHORT at geodynamics.org <mailto:CIG-SHORT at geodynamics.org>
> http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short
> <http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short>
>
>
>
> _______________________________________________
> CIG-SHORT mailing list
> CIG-SHORT at geodynamics.org <mailto:CIG-SHORT at geodynamics.org>
> http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short
> <http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short>
>
>
>
More information about the CIG-SHORT
mailing list