[CIG-SHORT] Nonlinear solve diverged_function_count

[Brad Aagaard]

Bobby,

Can you send a diagram of your problem? Is this a static problem or a 
quasi-static problem? Do the linear and nonlinear solves converge at 
every previous time step? Do this linear solves converge at every 
iteration for the time step when the nonlinear solve fails to converge?

Regards,
Brad


On 2/29/16 6:14 AM, Bobak Karimi 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>
> *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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