[Dune] FunctionSpace and DiscreteFunctions.

[Robert Kloefkorn]

Thimo Neubauer wrote:
> Hi,
> 
> On Wed, Dec 01, 2004 at 11:40:30AM +0100, Robert Kloefkorn wrote:
> 
>>From no on a function space lives on a certain level of the grid no 
>>matter wether this is the leaf level or a level of the grid hierarchy.
>>A discrete function still belongs to only one function space.
> 
> 
> This may be a silly question: how do I create a discrete function that
> lives on the grid seen by the LeafIterator, i.e. that only has DoFs on
> the leaves? Do I have to set a special level-parameter in the
> constructor for that? Or didn't I understand the scheme?
> 
> I'm asking because that would be the kind of functions our students
> should write visualization code for.

The question is not silly at all. There arise many questions.
Frist, the level can be ervery level like for the "level" case.

The more difficult problem, how to determin the size of the leaflevel, 
i.e. number of elements on leaf level and so on. For that you can either 
make a grid walk or create an index set (see leafindexset.hh in 
dune/grid/common/) that provides that kind of information. Now the 
functionspace gets an index set which provied an global dof number for 
entity and local dof number and knows the size (number of unknowns).
The index set can be a wrapper for the already existing grid indices 
(see defaultindexsets.hh) or create a new map (leafindexset.hh)
The dof mapper now uses this index set for creating an dof mapping like 
(3 dof on each element).
The functions space now knows from the dof mapper how many unkowns there 
are and the discrete functions( nothing else than an upgrades Vector) is 
created with that length of function space.

Many we should discuss this on the phone, because it too much to explain 
in english and per email.

Greetz

R

-- 

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

   Mathematisches Institut              Tel: +49 (0) 761 203 5642
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