[petsc-users] SNESNRICHARDSON with LibMesh

[Harshad Sahasrabudhe]

Hi Matt,

Thanks for your comments. I see that SNESNRICHARDSON has changed a lot from
3.4.3 to 3.5.3. What do I need to do to make the code compatible with both
3.4.3 and 3.5.3?

Thanks,
Harshad

On Tue, May 26, 2015 at 4:25 PM, Matthew Knepley <knepley at gmail.com> wrote:

> On Tue, May 26, 2015 at 3:07 PM, Harshad Sahasrabudhe <hsahasra at purdue.edu
> > wrote:
>
>> Hi Matt,
>>
>> Actually I just checked, I don't need to re-init the preconditioner
>> LibMesh solver.
>>
>> The wrapper is interfaced to the mesh and makes it easier to assemble the
>> system matrices. It also keeps track of constraints. The wrapper function PetscNonlinearSolver::solve
>> updates the system vectors and matrices, then calls SNESSolve. Thus, I
>> need to call PetscNonlinearSolver::solve instead of SNESSolve in
>> SNESApplyNPC.
>>
>> Do you mean wrap it in SNESSHELL?
>>
>
> Yes, exactly.
>
>   Thanks,
>
>      Matt
>
>
>> Thanks,
>> Harshad
>>
>> On Tue, May 26, 2015 at 3:25 PM, Matthew Knepley <knepley at gmail.com>
>> wrote:
>>
>>> On Tue, May 26, 2015 at 12:42 PM, Harshad Sahasrabudhe <
>>> hsahasra at purdue.edu> wrote:
>>>
>>>> Hi,
>>>>
>>>> I'm using LibMesh for meshing a non-linear equation. I want to use
>>>> NRichardson non-linear solver to solve the equation. I have a Newton trust
>>>> region non-linear solver as a pre-conditioner. Both these SNES are created
>>>> via the LibMesh NonlinearImplicitSystem and PetscNonlinearSolver wrappers.
>>>>
>>>> I need to re-init the LibMesh NonlinearImplicitSystem each time the
>>>> preconditioner is applied. Also, I need the preconditioner to be solved via
>>>> the LibMesh wrapper instead of directly through SNESSolve. How can make it
>>>> work this way? Any help is appreciated!
>>>>
>>>
>>> I think the easiest way is to have them both look like SNES objects.
>>> Then you can just call SNESSetNPC() or use -snes_npc_side left
>>> -npc_snes_type newtonls
>>>
>>> Can you explain what the LibMesh wrapper is doing that you you need? We
>>> could wrap that object in a SNES, but it sounds
>>> simpler to me to unwrap it.
>>>
>>>   Thanks,
>>>
>>>      Matt
>>>
>>>
>>>> Thanks,
>>>> Harshad
>>>>
>>>
>>>
>>>
>>> --
>>> 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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