[CIG-SHORT] Linear convergence for nonplanar faults

Tue Nov 8 16:00:04 PST 2016

Dear Josimar,

I don’t see the .cfg files you mention, but there is definitely something wrong with your linear convergence.  Actually, looking at your log file, the initial KSP Residual norm (7e16) is huge, and then the residual drops down to ~2e4.  What is your convergence tolerance?  

Charles

> On 9/11/2016, at 11:47 AM, Josimar Alves da Silva <jsilva.mit at gmail.com> wrote:
> 
> 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 <mailto: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-September/001123.html <http://lists.geodynamics.org/pipermail/cig-short/2012-September/001123.html>
> 
> 
> http://lists.geodynamics.org/pipermail/cig-short/2008-December/000453.html <http://lists.geodynamics.org/pipermail/cig-short/2008-December/000453.html>
> 
> 
> http://lists.geodynamics.org/pipermail/cig-short/2013-March/001320.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
> 
> 
> 
> 
> _______________________________________________
> 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>
> <log_with_fault_v02.out>_______________________________________________
> CIG-SHORT mailing list
> CIG-SHORT at geodynamics.org
> http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short

Charles A. Williams
Scientist
GNS Science
1 Fairway Drive, Avalon
PO Box 30368
Lower Hutt  5040
New Zealand
ph (office): 0064-4570-4566
fax (office): 0064-4570-4600
C.Williams at gns.cri.nz <mailto:C.Williams at gns.cri.nz>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.geodynamics.org/pipermail/cig-short/attachments/20161109/5892bdd4/attachment.html>