[petsc-users] Questions about the PetscDSSetResidual and Nedelec element.

[Matthew Knepley]

On Wed, Apr 5, 2023 at 10:00 AM neil liu <liufield at gmail.com> wrote:

> Thanks, Matt.
> 1) You mentioned that "PETSc calculates u_x, given the PetscFE and the
> coefficients (and the geometry).".
> Could you please direct me the source code that calculates u_x ?
>

https://gitlab.com/petsc/petsc/-/blob/main/src/dm/dt/fe/interface/fe.c#L2124


> 2) Yes. Raviart-Thomas is one type of Nedelec element (Hdiv also called
> divergence conforming). Do you support Hcurl (curl conforming) Nedelec
> element ?
>

Yes, you make them in the same way using the P and P^- spaces.

  Thanks,

      Matt


> On Tue, Apr 4, 2023 at 10:59 AM Matthew Knepley <knepley at gmail.com> wrote:
>
>> On Tue, Apr 4, 2023 at 10:45 AM neil liu <liufield at gmail.com> wrote:
>>
>>> Hello,
>>>
>>> I am learning this case,
>>> https://petsc.org/release/src/snes/tutorials/ex62.c.html
>>> . And try to make myself familiar with the FEM (PetscFE) there.
>>> Then I have several questions.
>>> 1)  PetscDSSetResidual
>>> <https://petsc.org/release/manualpages/DT/PetscDSSetResidual/>,
>>> For example, line 291,  PetscCall
>>> <https://petsc.org/release/manualpages/Sys/PetscCall/>(
>>> PetscDSSetResidual
>>> <https://petsc.org/release/manualpages/DT/PetscDSSetResidual/>(ds, 0,
>>> f0_quadratic_u, f1_u)), here, f0_quadratic_u and f1_u is function
>>> pointers. Where have the input parameter for these functions been
>>> calculated, e.g., u_x.
>>>
>>
>> Line 291 sets callback functions. These functions are actually called in
>> the loop over the mesh which calculates the residual.
>> PETSc calculates u_x, given the PetscFE and the coefficients (and the
>> geometry).
>>
>>
>>> If I want to check the values of these parameters before line 291, how
>>> to print that ?
>>>
>>
>> I output many thing with -dm_plex_print_fem 5, but I am not sure if I
>> print out the field jet. It would be easy to add.
>>
>>
>>> 2) Does PetscFE support Nedelec element? Will it be painful to add these
>>> modules myself ?
>>>
>>
>> What kind? I think we support them, but have no tests. Take a look at our
>> support for Raviart-Thomas
>>
>>
>> https://gitlab.com/petsc/petsc/-/blob/main/src/dm/dt/dualspace/impls/lagrange/tutorials/ex1.c#L78
>>
>> and see a use case here
>>
>>   https://gitlab.com/petsc/petsc/-/blob/main/src/snes/tutorials/ex24.c
>>
>>   Thanks,
>>
>>      Matt
>>
>>
>>> Thanks ,
>>>
>>> Xiaodong
>>>
>>>
>>
>> --
>> 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
>>
>> https://www.cse.buffalo.edu/~knepley/
>> <http://www.cse.buffalo.edu/~knepley/>
>>
>

-- 
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

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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