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

[Tobias Malkmus]

Hi all

You can find a BoundaryIdProvider in dune/fem/misc/boundaryidprovider.hh

     template< class Grid >
     struct BoundaryIdProvider;

But you will need set the "experimental-grid-extensions" flag, since you 
will need to have access to the grid implementation.

Switching to the boundarySegmentIndex() method of the intersections is 
still an open task.

Best Tobias


On 01/16/2014 09:12 AM, Andreas Dedner wrote:
> Hi.
> I agree that this is not optimal - we should think of an option to extract
> boundary id information from the macro grid file and store it somehow.
> Perhaps a Singleton object BoundaryIdProvider or
> perhaps a method on the GridPart::boundaryId(intersection)
> would do. I don't think using global coordinates is a viable solution....
> Best
> Andreas
>
> On 14.01.2014 15:37, Claus-Justus Heine wrote:
>> 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
>>
>>
>>
>>
>>
>>
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-- 
Tobias Malkmus                 <tomalk at mathematik.uni-freiburg.de>

Mathematisches Institut               Tel: +49 761 203 5627
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