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

[Justin Chang]

Matt,

So do I use:

"-pc_type bjacobi -sub_pc_type lu"

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
>
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