[Dune] Capability hasLevelIterator?

[Andreas Dedner]

We should be very carfull with introducing Capabilities - I'm
not saying we should not do it, but just to be carfull.
For example it was also difficult to include level iterators into
Alberta and with a Capability we would probaply have never done
it. For that I would suggest to add more Default Implementations -
A Level(0) Iterator and a hierarchicIterator is all it takes...
It might not be efficient but it works and a grid can be
implemented with all features and can then its performace can
slowly be improved.
In fact there are many more examples of possible
default Implementations (for example geometries just require
the coordinated of an entity in the numbering given by
the Reference element, everything else is always the same).
Having a really slime interface with default implementations and
the possibility of optimization later on, would really
improve the implementation of new grids...

Just some thoughts
Andreas
Markus Blatt wrote:
> Hi,
> 
> On Wed, Oct 18, 2006 at 10:23:19AM +0200, Oliver Sander wrote:
> 
>>I think making level iterators optional is a point worth considering.
>>Already it seems to me (am I right?) that one grid implementation
>>doesn't implement them.
>>
> 
> 
> speaking for Stuttgart again, I would like to continue the discussion
> whether to introduce a new Capability hasLevelIterator.
> 
> We think that (at least for the current code) with exception of
> implementation of geometric multigrid methods the LevelIterator is
> not mandatory. There are already grids (e. g. NetworkGrid) under the Dune
> Interface that cannot support LevelIterators in an efficient (and
> complete) way and there might be more implementations with this inability
> 
> Introducing the hasLevelIterator capability would allow even those
> implementations under the Dune Interface without breaking the Grid
> tests.
> 
> Therefore Stuttgart votes for introducing te hasLevelIterator
> capability.
> 
> What is the opinion in Freiburg concerning this issue?
> 
> Cheers,
> 
> Markus Blatt
> 
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