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

[neil liu]

Thanks, Matt.
When you said "P and P minus space" , do you have some references about
this terminology to build the Hdiv and Hcurl for triangles or tetrahedra?


On Wed, Apr 5, 2023 at 10:12 AM Matthew Knepley <knepley at gmail.com> wrote:

> 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/>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20230405/5f359458/attachment-0001.html>