[Dune] (no subject)

[Sven Marnach]

Hi Oliver,

thanks for your fast reply.

Oliver Sander schrieb am Mo, 29. Okt 2007, um 14:14:53 +0100:
> >2. It seems quite inefficient to me that I really have to construct an
> >   entity just to get the index, but the map method of the Mapper
> >   interface requires this.
> 
> What index do you expect to get if don't have an entity?

You could pass an EntityPointer instead of an Entity.  Or you could
ask for the index of some subentity like with the subIndex method of
the IndexSet interface.  (I think I will try the latter solution with
a modified implementation of the Multiple.....Mapper.)

> >   Oliver, could you give me a hint how to implement it?  Is it
> >   possible to do this without knowing anything about the UG
> >   internals?  Are the EntityPointers and Entities of codim 1
> >   implemented at all?
> >  
> No, the entities of codim 1 are not implemented at all.
> Long time ago we decided that only the entities of codimension
> 0 and dim were mandatory, and indeed there is a capability
> trait 'hasEntity' which tells you about the available entities.
> 
> Implementing edge and face iterators for UGGrid is not really
> difficult, but you have to know some UG internals.  Faces
> in particular don't actually exist in UG and you have to trick
> your way around.

So I think it isn't practical for me to implement this.  I'd like both
the 2D case and the 3D case to work, so it sounds as if it would be
quite a lot of work.  And I don't need the entities at all, I just
need some index of them.  It is probably both easier to implement and
more (runtime-)efficient to write some kind of mapper with the ability
to map subentities.

Nonetheless thanks for your help!

Sven