[petsc-users] Questions about PetscTabulation for finite element basis, and PetscViewerVTK for saving cell data

[Matthew Knepley]

On Mon, May 26, 2025 at 4:45 AM Gong Yujie <yc17470 at connect.um.edu.mo>
wrote:

> Dear PETSc developers,
>
> I have a code that uses PETSc to solve the elasticity problem with the
> finite element discretization written by myself.  I found there is a part
> called "PetscTabulation" that stores the basis functions. I would like to
> inquire about this part that can I use this part for achieving high order
> element? In detail, how does the basis functions be evaluated and in which
> file can I find the basis functions? I'm thinking about using
> PetscTabulation and PetscQuadrature to achieve a high order element. Is
> this doable?
>

PetscTabulation just holds the evaluation of the basis functions at the
quadrature points (or any other points). PetscQuadrature generates
quadrature points on polytopes, with some quadrature order. You can use
them independently of PetscFE to do this job.


> The next question is can I output a vector that the unknown is defined on
> each element (not point) using VecView? I think this question relates to
> the PetscViewer for VTK.
>

I have never gotten higher order elements to work in VTK. What I do is
refine the mesh and output on cells or vertices.

  Thanks,

     Matt


> Thanks in advance for your help!
>
> Best Regards,
> Jerry
>


-- 
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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