[Dune] AMG and block matrizes

[Christian Engwer]

> Sorry, but I just can't help it :-)

Well, dumping the code into the mail doesn't make it any easier. I
didn't ask for a solution. I wanted to known whether someone already
succeded.

> Seriously, you are probably using a criterion that is not correctly
> setup. Try something like this:
> 
> typedef
> Dune::Amg::CoarsenCriterion<Dune::Amg::SymmetricCriterion<typename
                                         ^^^
This won't work, my matrizes aren't symetric.

> DG::Matrix,Dune::Amg::RowSum> >
>     Criterion;
> typedef Dune::SeqILU0<typename DG::Matrix,BVector,BVector> Smoother;
> typedef Dune::MatrixAdapter<typename DG::Matrix,BVector,BVector> Operator;
> typedef Dune::Amg::AMG<Operator,BVector,Smoother> AMG;

I found out that it is actually a bug in paamg. We can look into the
details when you are back in Stuttgart :-)

Christian