[dune-fem] Design of boundary classification, e.g. fem-poisson in school code

[Claus-Justus Heine]

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Hi,

now that the boundaryId() method has been removed from the dune-grid
interface (... unless BLAH_EXPERIMENTAL ...) one in principle has only
the geometry itself to decide whether a given boundary facet belongs
to a specific part of the boundary. If I then think of the layout of
the example implementation of fem-poisson in the school-code, for
example, then we have (simplified) the following way to construct the
final algorithm

problem -> model -> fem-scheme -> algorithm

If now the model has no other chance than to look at the geometry to
assign suitable boundary conditions, then the model must have some
knowledge about the computational domain. This seems to be somewhat
inconvenient: when changing the macro triangulation (e.g. make it
twice as large or whatever) then one also has to adjust the model. At
least to me this seems to suggest that the definition of the
computational domain should be part of the model. Defining the macro
triangulation in the parameter file does not seem to fit this layout.

Cheers,

Claus





- -- 
Dr. Claus-Justus Heine
Institut für Angewandte Analysis und Simulation
* Numerische Mathematik für Höchstleistungsrechner
Universität Stuttgart

Fon: +49 (0) 711 - 685 65558
Fax: +49 (0) 711 - 685 65507
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