[CIG-SHORT] Nonlinear solve diverged_function_count

[Charles Williams]

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> 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 <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
> 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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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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