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

[neil liu]

Thanks a lot, Matt. I indeed did some research using Hcurl Nedelec element
to solve 3D maxwell equations. I didn't consider too much math related to
Nedelec element (P and P minus). That is why I would like some references
from you.

Could you please direct me the source code defining the Hdiv basis
functions?
Thanks,

On Wed, Apr 5, 2023 at 11:16 AM Matthew Knepley <knepley at gmail.com> wrote:

> On Wed, Apr 5, 2023 at 10:36 AM neil liu <liufield at gmail.com> wrote:
>
>> 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?
>>
>
> The canonical reference is
> https://www-users.cse.umn.edu/~arnold//papers/acta.pdf but that was hard
> to understand for me. There must
> be a better reference but I do not know it.
>
>   Thanks,
>
>      Matt
>
>
>> 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/>
>>>
>>
>
> --
> 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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