[Dune] Local p-refinement in DUNE?

[Christoph Grüninger]

Hi Bryan,
I never used the local p-refinement myself, but from reading the code I
got the impression that the problem is within PDELab and you should not
need to define the required class yourself. Probably something broke in
the past. You might want to have a look in into the commit history of
the related files to understand what happened.
dune-localfunctions should be unrelated, PDELab creates the variables FE
spaces itself, on top of non-variable spaces from localfunctions.

Bye
Christoph

Am 27.03.2018 um 18:44 schrieb Bryan Doyle:
> Hello Christian,
> Thank you for your response! Having a non-conforming FEM is not an issue
> for me at this point, so I have been looking into the variableqkdgfem.hh
> implementation as per your suggestion, and think that this is exactly
> what I was looking for.
> 
> However, I had a follow-up question I was hoping to get feedback on: on
> line 24 of variableqkdgfem.hh, "Dune::QkDGLocalFiniteElement" is called,
> and my compiler complains that this does not name a template type.
> Should this be defined for me somewhere in dune/localfunctions/, where
> classes like "QkLocalFiniteElement" and "PkLocalFiniteElement" are
> defined? I don't see this anywhere in my code (I am using v2.5.1), so I
> was curious if I am missing some file or if I have to define the class
> "QkDGLocalFiniteElement" myself. I appreciate any feedback you or anyone
> else may have!
> 
> Thank you for your time,
> Bryan
> 
> On Thu, Mar 22, 2018 at 2:15 PM, Christian Engwer
> <christian.engwer at uni-muenster.de
> <mailto:christian.engwer at uni-muenster.de>> wrote:
> 
>     Dear Bryan,
> 
>     there is a limited amount of support for p-refinement. There are
>     different variable*fem.hh implementations of DG bases with variable
>     polynomial degree. You can specify the degree via a non-standard
>     method
>           void setOrder (const EntityType& e, unsigned int p)
> 
>     This should work quite straight forward. If you want to use conforming
>     FEM things are a bit more complicated. You could implement something
>     very similar to the current implementation, but how do you ensure
>     conformity. This has to be done either by the finite-element-map by
>     providing a specific finite-element which has a lower degree on a
>     face, or by introducing appropriate constraints. Currently
>     dune-localfunctions is not able to create such mixed degree elements
>     and I don't think this is a viable apporach. So you want the
>     constraints... PDELab has a couple of constraints implementations, but
>     non that will work for this case.
> 
>     So first question is ... what exactly do you need?
> 
>     Best
>     Christian
> 
> 
>     > Hello,
>     > I am attempting to implement the ability to locally refine the
>     polynomial
>     > degree of the function space within my DUNE code, using PDELab. My
>     first
>     > thought was to use DUNE's "CompositeGridFunction" functionality,
>     but I do
>     > not believe this allows for modification of the grid space degree
>     across
>     > the domain.
>     >
>     > To do this, would I instead have to code my own finite-element map
>     whose
>     > degree changes across the domain, and make a grid function space
>     out of
>     > that? Are there any tutorials available where such refinement is
>     done? I
>     > don't have any ideas of a starting point, so any thoughts or
>     pointers would
>     > be greatly appreciated!
>     >
>     > Thank you,
>     > Bryan
> 
> 
> 
> 
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