[CIG-SHORT] Linear convergence for nonplanar faults

[Josimar Alves da Silva]

Dear Charles and Brad,

Thank you for following up on my question. I implemented the changes you
suggested and it did not improve the convergence. I am attaching the log
file for you reference.

All the other parameters of the previous files were kept unchanged, except
the length_scale = 500*m.

Let me know if you have any other suggestion.
Thank you
Josimar

On Tue, Nov 8, 2016 at 4:46 PM, Brad Aagaard <baagaard at usgs.gov> wrote:

> Josimar,
>
> Your solver settings in pylithapp.cfg are obsolete. To use fieldsplit and
> the custom preconditioner, please use the solver settings in
> share/settings/solver_fault_fieldsplit.cfg (shown below). Note that
> instead of 0/1 for the field, we now use names
> (displacement/lagrange_multiplier).
>
> These settings will only work well if there is a fault. Without a fault,
> you can just use ML as the preconditioner. See examples/3d/hex8/step02.cfg
> (just use pc_type = ml).
>
> Regards,
> Brad
>
>
> [pylithapp.problem.formulation]
> split_fields = True
> matrix_type = aij
> use_custom_constraint_pc = True
>
> [pylithapp.petsc]
> fs_pc_type = fieldsplit
> fs_pc_use_amat =
> fs_pc_fieldsplit_type = multiplicative
> fs_fieldsplit_displacement_pc_type = ml
> fs_fieldsplit_lagrange_multiplier_pc_type = jacobi
> fs_fieldsplit_displacement_ksp_type = preonly
> fs_fieldsplit_lagrange_multiplier_ksp_type = preonly
>
>
>
>
> On 11/08/2016 11:00 AM, Josimar Alves da Silva wrote:
>
>> Dear Brad, Matt and Charles,
>>
>> I am running Pylith for a 2D friction model with gravity for a nonplanar
>> fault. I am finding that the linear solver does not converge when the
>> fault is included on the model. When the fault is not included on the
>> model the linear solver takes roughly 500 to 1000 iterations to
>> converge. Please refer to the attached "log_no_fault.cfg" file.
>>
>> The three links below show previous discussions on linear convergence:
>>
>> http://lists.geodynamics.org/pipermail/cig-short/2012-Septem
>> ber/001123.html
>>
>>
>> http://lists.geodynamics.org/pipermail/cig-short/2008-Decemb
>> er/000453.html
>>
>>
>> http://lists.geodynamics.org/pipermail/cig-short/2013-March/001320.html
>>
>>
>>
>> As pointed out by Charles previously and also discussed on the links
>> above, overall, it seems that there are 3 main causes for convergence
>> issues: 1) Poor quality mesh; 2) incorrect solver settings; 3) Poor
>> setup/initial conditions.
>>
>>
>> For my set up, I am unable to make the linear solver to converge.
>>
>>
>> This is what I have done so far, based on recommendations from previous
>> discussions:
>>
>>
>> 1) Make sure that the mesh has condition number and aspect ratios <1.5.
>> Please see attached presentation for histograms.
>>
>> 2) used the solver parameters shown
>> on share/settings/solver_fault_fieldsplit.cfg
>>
>>
>> I would like to know if there is anything else that I can do in order to
>> make the linear solver to converge. Any other advices to improve my
>> simulation would be very much appreciated.
>>
>>
>> You can find attached the pylith .cfg files that I am using and also the
>> log files for the case without the fault (log_no_fault.out) and with the
>> fault (log_with_fault.out).
>>
>>
>> I run my simulation using:
>>
>>
>> 1) pylith no_fault.cfg > log_nor_fault.out
>>
>> 2) pylith no_fault.cfg   fault.cfg > log_with_fault.out
>>
>>
>>
>> Thank you in advance for you help,
>>
>> Josimar
>>
>>
>>
>>
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>>
>>
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