[petsc-users] DIVERGED_LINEAR_SOLVE in SNES

[Matthew Knepley]

On Fri, Sep 27, 2019 at 9:19 AM Li Luo via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Thank you for the suggestions, I'll try it.
>

I think an easier way to do what you want is

  -snes_max_linear_solve_fail 10

from


https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/SNES/SNESSetMaxLinearSolveFailures.html

  Thanks,

     Matt


> Best,
> Li
>
> On Fri, Sep 27, 2019 at 5:27 AM Smith, Barry F. <bsmith at mcs.anl.gov>
> wrote:
>
>>
>>   Li,
>>
>>    It is possible, but as Hong said probably never appropriate.
>> Especially if KSP has iterated for 10,000 iterations. If you want SNES to
>> "try" the direction given by a failed solve you should use a much smaller
>> maximum number of iterations for KSP.
>>
>>    Anways, to do what you desire
>>
>> #include <petsc/private/kspimpl.h>
>>
>> call KSPSetPostSolve() and in your post solve() function simply do
>> ksp->reason = KSP_CONVERGED_ITS.
>>
>>  Barry
>>
>>
>>
>>
>> > On Sep 26, 2019, at 10:58 AM, Zhang, Hong via petsc-users <
>> petsc-users at mcs.anl.gov> wrote:
>> >
>> > Li :
>> > You can use '-ksp_max_it 20000' to change maximum iteration count.
>> However, it does not make sense to continue after it fails at 10000
>> iterations. You should figure out why linear solver diverges. Run your code
>> with '-ksp_monitor' or '-ksp_monitor_true_residual'.
>> > Hong
>> >
>> > Dear developer,
>> >
>> > I am using SNES for solving a nonlinear system.  For some cases, SNES
>> diverged -3 with "DIVERGED_LINEAR_SOLVE" when the linear solver reached its
>> maximum iteration count (i.e -ksp_max_it 10000).
>> > Is that possible to let SNES continue even though the linear solver
>> reaches the maximum number of iterations? Just take the result at 10000 for
>> the Jacobian solution and then update the Newton step?
>> >
>> > Best,
>> > Li
>> >
>> >
>> >
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>>
>
> --
>
> Postdoctoral Fellow
> Extreme Computing Research Center
> King Abdullah University of Science & Technology
> https://sites.google.com/site/rolyliluo/
>
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https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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