[CIG-SHORT] PyLith Convergence issue - DIVERGED_FUNCTION_COUNT and CONVERGED_SNORM_RELATIVE
Josimar Alves da Silva
jsilva.mit at gmail.com
Thu Jun 22 14:49:25 PDT 2017
Brad,
Thanks for the remind. Here it is:
https://www.dropbox.com/sh/sxiburbvru670n3/AAD3sLLHVPp-E-FKo4oQwf23a?dl=0
thank you
Josimar
On Thu, Jun 22, 2017 at 5:28 PM, Brad Aagaard <baagaard at usgs.gov> wrote:
> 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/c
>> gi-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-sh
>> ort
>> <http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-s
>> hort>
>>
>>
>>
>> _______________________________________________
>> 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
> http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.geodynamics.org/pipermail/cig-short/attachments/20170622/22213257/attachment.html>
More information about the CIG-SHORT
mailing list