[petsc-users] KSP diverging

[Matthew Knepley]

On Thu, Dec 22, 2011 at 7:37 PM, Mohamad M. Nasr-Azadani
<mmnasr at gmail.com>wrote:

> Thanks so much Jed for your prompt response. I will start experimenting
> with all the suggestions.


dtol failure is impossible for GMRES (and CG). Consider checking with that.

   Matt


> Best,
> Mohamad
>
>
> On Thu, Dec 22, 2011 at 5:31 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>
>> On Thu, Dec 22, 2011 at 19:20, Mohamad M. Nasr-Azadani <mmnasr at gmail.com>wrote:
>>
>>> Any hints on what is happening here or how I could narrow it down?
>>
>>
>> I would start by following the general advice in the FAQ
>>
>> http://www.mcs.anl.gov/petsc/documentation/faq.html#kspdiverged
>>
>>
>>> I know that we had an early discussion on the convergnce for the
>>> incompressible CFD problems and boomerAMG preconditioning,
>>
>>
>> That was about solving the coupled system. That shouldn't be an issue for
>> the Poisson problem.
>>
>>
>>> but it seems that for this case, that is the only one that does not blow
>>> up for most of the time integration I have.
>>
>>
>> Since this problem only occurs after long time integration, you might
>> consider writing out the model state when you see divergence so that you
>> can experiment with alternative methods quickly.
>>
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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