[petsc-users] DIVERGED_NANORINF for CG/Bjacobi for transient diffusion

[Matthew Knepley]

On Wed, Mar 30, 2016 at 4:26 PM, Justin Chang <jychang48 at gmail.com> wrote:

> Matt,
>
> So do I use:
>
> "-pc_type bjacobi -sub_pc_type lu"
>

The above.

   Matt


> or this:
>
> "-sub_pc_type lu"
>
> Thanks,
> Justin
>
> On Wed, Mar 30, 2016 at 4:23 PM, Matthew Knepley <knepley at gmail.com>
> wrote:
>
>> On Wed, Mar 30, 2016 at 4:18 PM, Justin Chang <jychang48 at gmail.com>
>> wrote:
>>
>>> Hi all,
>>>
>>> I am getting this error:
>>>
>>> Linear solve did not converge due to DIVERGED_NANORINF
>>>
>>> when solving an FEM for transient diffusion using hexahedron elements.
>>> The problem is highly heterogeneous (i.e., dispersion tensor with varying
>>> cell-centered velocity) and normally CG/Bjacobi has done well for me. If I
>>> did CG/Jacobi, my solver would require nearly 7000 iterations, but would
>>> get the "expected" solution.
>>>
>>> What does the above error mean? And what could I do to address it?
>>>
>>
>> Almost certainly ILU craps out. Try using LU as the subsolver instead.
>>
>>   Matt
>>
>>
>>> Thanks,
>>> Justin
>>>
>>
>>
>>
>> --
>> 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
>>
>
>


-- 
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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