[CIG-SHORT] PyLith Convergence issue - DIVERGED_FUNCTION_COUNT and CONVERGED_SNORM_RELATIVE
Josimar Alves da Silva
jsilva.mit at gmail.com
Fri Jun 23 07:04:31 PDT 2017
Ok sounds, good. thank you so much.
Best,
Josimar
On Fri, Jun 23, 2017 at 10:00 AM, Brad Aagaard <baagaard at usgs.gov> wrote:
> On 06/23/2017 06:24 AM, Josimar Alves da Silva wrote:
>
>> Brad,
>>
>> Just to let you know that I sorted it out this problem.
>>
>> I set "open_free_surface=True" instead of False. My understanding
>> regarding why it was not working is because I am applying tensile tractions
>> on the fault to balance out the normal stress, however this could
>> potentially cause a problem with the fault node that is on edge of the
>> domain (right side on the fault, on the interface between the displacement
>> BC and the zero displacement BC of my geometry). Do you think this could
>> potentially be the problem ? I
>>
>
> Maybe. It is difficult to diagnose some of these issues without a better
> understanding of what you are trying to model. For example, I don't
> understand why you are applying tensile tractions. A simple sketch of what
> you are trying to model would help. We can talk about this at the workshop
> next week.
>
> In setting up a new fault friction example, I may be encountering some
> similar issues to what you are finding related to rate- and state-friction
> and convergence issues for a through-going fault. I have several ideas on
> what the source of this might be, but need to do some more testing to zero
> in on the problem (I doubt I will be able to get to this before next week).
>
> Regards,
> Brad
>
>
>
>> I haven't changed anything on the solver parameterization. You can find
>> all the log files and the pylith_parameters.json file here:
>> https://www.dropbox.com/sh/by2vgqadgbsk1fs/AACENG_kCXygHa3dsdEyNAf-a?dl=0
>>
>> thank you,
>> Josimar
>>
>>
>> On Thu, Jun 22, 2017 at 5:49 PM, Josimar Alves da Silva <
>> jsilva.mit at gmail.com <mailto:jsilva.mit at gmail.com>> wrote:
>>
>> Brad,
>>
>> Thanks for the remind. Here it is:
>> https://www.dropbox.com/sh/sxiburbvru670n3/AAD3sLLHVPp-E-FKo
>> 4oQwf23a?dl=0
>> <https://www.dropbox.com/sh/sxiburbvru670n3/AAD3sLLHVPp-E-FK
>> o4oQwf23a?dl=0>
>>
>> thank you
>> Josimar
>>
>> On Thu, Jun 22, 2017 at 5:28 PM, Brad Aagaard <baagaard at usgs.gov
>> <mailto: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
>> <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>
>> <mailto: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>
>> <mailto: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>
>> <mailto: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> <mailto: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
>>
>>
>>
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