[CIG-SHORT] Nonlinear solve diverged_function_count

Brad Aagaard baagaard at usgs.gov
Wed Mar 2 12:36:44 PST 2016 

Bobby,

Are you imposing compressive fault normal tractions? Your BC don't look 
like they will lead to compressive stresses on the faults as deformation 
continues, especially with nonplanar faults.

Regards,
Brad


On 03/02/2016 12:31 PM, Bobak Karimi wrote:
> Hi Charles,
>
> We are using a model similar to that in step12.cfg (static friction with quasi-static dirichlet boundary conditions).
>
> I'll give the single through-going fault a try.
>
> Bobby
>
>
>
> Sent via the Samsung Galaxy Note5, an AT&T 4G LTE smartphone
>
>
> -------- Original message --------
> From: Charles Williams <willic3 at gmail.com>
> Date: 03/02/2016 3:21 PM (GMT-05:00)
> To: cig-short <cig-short at geodynamics.org>
> Subject: Re: [CIG-SHORT] Nonlinear solve diverged_function_count
>
> Hi Bobby,
>
> I’m not sure how to increase the value for ksp_sub.  I would have to dig around in the code or documentation.  Can you remind me again what sort of frictional model you are using, and what sort of friction values?  Also, what are you using for a normal stress?
>
> As a further test to isolate the problem, maybe you can turn off everything except for one throughgoing fault, and see if that converges.
>
> Cheers,
> Charles
>
>
> On 3/03/2016, at 2:11 AM, Bobak Karimi <bkarimi at clarion.edu<mailto:bkarimi at clarion.edu>> wrote:
>
> Hi Charles,
>
> To make it run faster, and actually make it past the first timestep, we have increased our tolerances significantly: ksp_atol (1.0e-7) < zero_tolerance (1.0e-6) < snes_atol (1.0e-5). Turning off the faults gave us results where the deformation field from the quasi-static boundaries looked as expected, so I don’t believe the problem is with our mesh. I’ve notice that when we increase the mesh discretization that the simulations run longer (as in they make it to further time steps) before ending with the DIVERGED_FUNCTION_COUNT error. We are working on implementing the exact solver.
>
> In the meantime, the ksp for the faults seems to be what is causing the error we are receiving. The ksp_sub has a divergence set at 10,000. Is there a way to increase this?
>
> Thanks,
> Bobby
>
>
> From: CIG-SHORT [mailto:cig-short-bounces at geodynamics.org] On Behalf Of Charles Williams
> Sent: Monday, February 29, 2016 8:26 PM
> To: cig-short <cig-short at geodynamics.org<mailto:cig-short at geodynamics.org>>
> Subject: Re: [CIG-SHORT] Nonlinear solve diverged_function_count
>
> Hi Bobby,
>
> Two things I might try are:
>
> 1.  Turn off the faults and see what convergence looks like with just your external boundary conditions.  This will make sure there is not some issue with your mesh or normalization.
> 2.  If the linear convergence looks good in that case, try using the exact solver for the fault and see if that works.
>
> Cheers,
> Charles
>
>
> On 1/03/2016, at 10:05 AM, Bobak Karimi <bkarimi at clarion.edu<mailto:bkarimi at clarion.edu>> wrote:
>
> 1.      Is this a 2D or 3D problem, and how large is it?
> a.       It is a 2D problem and has around 13,000 cells (dimension wise it’s about 400 km long and 300 km wide)
> 2.      Is it a single fault or multiple faults?
> a.       Multiple faults. One through-going, and several intersecting faults.
> 3.      What does the convergence for the linear solver look like (slow convergence, large number of iterations, etc.)?
> a.       Convergence is pretty slow, iterations around 2,800.
> 4.      Have you tried using an exact solver for the fault (look in pylith/share/settings)?
> a.       We haven’t tried an exact solver.
> 5.      Is your mesh of high quality?
> a.       The mesh quality is high quality.
>
>
> From: CIG-SHORT [mailto:cig-short-bounces at geodynamics.org] On Behalf Of Charles Williams
> Sent: Monday, February 29, 2016 3:00 PM
> To: cig-short <cig-short at geodynamics.org<mailto:cig-short at geodynamics.org>>
> Subject: Re: [CIG-SHORT] Nonlinear solve diverged_function_count
>
> I guess it might help to know more about your problem and what the current convergences are like.  I see that you have really large values for your maximum iterations.  Have those been necessary?  Here are some questions for you:
>
> 1.  Is this a 2D or 3D problem, and how large is it?
> 2.  Is it a single fault or multiple faults?
> 3.  What does the convergence for the linear solver look like (slow convergence, large number of iterations, etc.)?
> 4.  Have you tried using an exact solver for the fault (look in pylith/share/settings)?
> 5.  Is your mesh of high quality?
>
> That’s all I can think of right now, but let me know if you make any progress on this.
>
> Cheers,
> Charles
>
>
> On 1/03/2016, at 3:14 AM, Bobak Karimi <bkarimi at clarion.edu<mailto:bkarimi at clarion.edu>> wrote:
>
> Hi Charles,
>
> The tight factors for rtol were purposeful to force the controlling tolerance to be the atol. This was what I had gleaned from session iv, step03 in the 2015 pylith tutorial. My PetSc values are below:
>
> # PETSc
> # ----------------------------------------------------------------------
> # Set the solver options.
>
> [pylithapp.petsc]
>
> # Preconditioner settings.
> pc_type = asm
> sub_pc_factor_shift_type = nonzero
>
> # Convergence parameters.
> ksp_rtol = 1.0e-20
> ksp_atol = 1.0e-11
> ksp_max_it = 1000000
> ksp_gmres_restart = 100
>
> # Linear solver monitoring options.
> ksp_monitor = true
> ksp_view = true
> ksp_converged_reason = true
>
> # Nonlinear solver monitoring options.
> snes_rtol = 1.0e-20
> snes_atol = 1.0e-9
> snes_max_it = 1000000
> snes_monitor = true
> snes_view = true
> snes_converged_reason = true
> snes_error_if_not_converged = true
>
> # PETSc summary -- useful for performance information.
> log_summary = true
>
> # Uncomment to launch gdb when starting PyLith.
> # start_in_debugger = true
>
>
> # End of file
>
> From: CIG-SHORT [mailto:cig-short-bounces at geodynamics.org] On Behalf Of Charles Williams
> Sent: Sunday, February 28, 2016 2:57 PM
> To: cig-short <cig-short at geodynamics.org<mailto:cig-short at geodynamics.org>>
> Subject: Re: [CIG-SHORT] Nonlinear solve diverged_function_count
>
> Dear Bobby,
>
> It’s hard to say without seeing all of your settings, but those seem like pretty tight values for rtol.  Is there a reason you are setting them so small?
>
> Cheers,
> Charles
>
>
> On 27/02/2016, at 6:36 AM, Bobak Karimi <bkarimi at clarion.edu<mailto:bkarimi at clarion.edu>> wrote:
>
> Hello,
>
> I recently got this error on a simulation I was running, and am not sure how to apply a fix for it:
>
> Nonlinear solve did not converge due to DIVERGED_FUNCTION_COUNT iterations 2743
>
> My KSP and NSES rtol = 1.0e-20
> KSP_atol = 1.0e-11
> SNES_atol = 1.0e-9
>
> The zero-tolerance on my faults is 1.0e-10.
>
> Any help would be much appreciated,
>
> Thanks!
> Bobby
>
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> Charles A. Williams
> Scientist
> GNS Science
> 1 Fairway Drive, Avalon
> PO Box 30368
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>
> _______________________________________________
> CIG-SHORT mailing list
> CIG-SHORT at geodynamics.org<mailto:CIG-SHORT at geodynamics.org>
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>
> 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>
>
> _______________________________________________
> 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
>
> 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>
>
> _______________________________________________
> 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
>
> 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>
>
>
>
>
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> CIG-SHORT mailing list
> CIG-SHORT at geodynamics.org
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