[Dune] EntitySeed.

[Robert Kloefkorn]

Hello Dune,

I started to implemented the interface for EntitySeed. The Interface
class is missing currently. I just added the concept and proper default
implementations which should make the transition phase much easier.

The changes are the following:

- type extraction via Grid::Codim< cd > :: EntitySeed
- method EntitySeed seed() const;  on the class Entity
- method EntityPointer grid.entityPointer ( seed ) const ;

EntitySeed should allow storage of Entities with as minimal memory
consumption as possible. From this seeds the entities can be
reconstructed if needed again.

All grids not implementing the EntitySeed yet and using the default
GridTraits from grid.hh will support this feature via EntityPointer,
which is the current (inappropriate) default value for an EntitySeed.
For Grid implementers: To have this default implementation the class
Grid should be derived form GridDefaultImplementation and the EntityImpl
should be derived from EntityDefaultImplementation.

I tested all implementations in dune-grid (except UGGrid because of
missing installation). All tests compiled and worked.

A proper check for this entity seeds has been added to the gridcheck.cc

If you encounter any problem, just let me know.

Best regards,

Robert

-- 

  Dr. Robert Klöfkorn         <robertk at mathematik.uni-freiburg.de>

  Mathematisches Institut              Tel: +49 (0) 761 203 5631
  Abt. für Angewandte Mathematik       Fax: +49 (0) 761 203 5632
  Universität Freiburg
  Hermann-Herder-Str. 10
  79104 Freiburg

  http://www.mathematik.uni-freiburg.de/IAM/homepages/robertk