[dune-pdelab] Hanging Nodes

[schauer]

Hi Felix,

thanks for your answer. I tried to have an insight into the way the
constraints are upset and treated in the grid operator space, but
honestly, like so many source code parts in pdelab, when it comes to the
details, it seems quite confusing to me.

Regards

Volker 



Am Mittwoch, den 23.03.2011, 17:02 +0100 schrieb Felix Heimann:
> Hi Volker,  
> actually i think you are correct with all your assumptions. About one
> week ago i noticed that the hanging node howto example does not work
> anymore. However i was not yet able to look into it. I'll try to
> tackle it next week. However, if you find the problem before me, feel
> free to send a patch. 
> 
> Best Regards, Felix
> 
> Durch MOTOBLUR™ verbunden
> 
> 
> -----Ursprüngliche Nachricht-----
>         Von: schauer <schauer at mechbau.uni-stuttgart.de>
>         An: dune-pdelab <dune-pdelab at dune-project.org>
>         Gesendet: Mi, 23 Mrz 2011, 16:30:04 MEZ
>         Betreff: [dune-pdelab] Hanging Nodes
>         
>         
>         Dear PDELabers,
>         
>         I try to implement hanging nodes together with Dirichlet
>         constraints. I 
>         acted as in the poisson example of the pdelab howto. 
>         
>         But now some things appear strange to me:
>         
>         - The transformation of a vector with 
>         gos.backtransform 
>         
>         as well as
>         
>         gos.forwardtransform
>         
>         only seem to multiply the hanging node entry of the
>         input-vector 
>         with a value from the constraints container without any kind
>         of
>         interpolation with the neighbouring nodes - so the
>         transformation
>         matrix is diagonal and in my case the backward transformation
>         after a
>         forward transformation do not give the original vector but in
>         my case 
>         these transformations even seem to be identical. 
>         
>         I then looked at the constraints container with the verbosity
>         flag in
>         the constraints call, and also saw that all the hanging nodes
>         had just
>         one entry with the same line as row index, e.g. like:
>         
>         266: (266,0.25) 
>         267: (267,0.25) 
>         268: (268,0.25) 
>         275: (275,0.5) 
>         276: (276,0.5) 
>         278: (278,0.5) 
>         
>         which also consists of only one value in every row (somehow I
>         supposed
>         the neighbouring, non-constrained nodes should show up here). 
>         
>         The row entries of the resulting matrix at a hanging node
>         position were
>         trivial, which seems to be fine to me, but I don't think that
>         the other
>         rows were changed correctly (though I didn't verify).
>         
>         I suppose these things can also be verified on the hanging
>         nodes example
>         poisson.cc of the pdelab-howto.
>         
>         
>         So is the way the constraints container gets filled for the
>         hanging
>         nodes wrong - or am I not correct with some of my
>         assumptions ? 
>         
>         Thanks
>         
>         Volker
>         
>         
>         
>         
>         
>         -- 
>         
>         _/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
>         
>         Volker Schauer (Dipl.Phys)
>         
>         Institute of Applied Mechanics (Civil Engineering), Chair 1
>         University of Stuttgart
>         Pfaffenwaldring 7
>         D-70569 Stuttgart
>         GERMANY
>         
>         Phone ++49 (0)711-68560044
>         email: schauer at mechbau.uni-stuttgart.de
>         
>         
>         _______________________________________________
>         dune-pdelab mailing list
>         dune-pdelab at dune-project.org
>         http://lists.dune-project.org/mailman/listinfo/dune-pdelab

-- 

_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/

Volker Schauer (Dipl.Phys)

Institute of Applied Mechanics (Civil Engineering), Chair 1
University of Stuttgart
Pfaffenwaldring 7
D-70569 Stuttgart
GERMANY

Phone ++49 (0)711-68560044
email: schauer at mechbau.uni-stuttgart.de