[petsc-users] SNESNRICHARDSON with LibMesh

[Matthew Knepley]

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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