[Dune] Solving Ax=b with A being a matrix of sparse matrices

[Markus Blatt]

On Tue, Mar 04, 2008 at 01:43:29PM +0100, Thomas Witkowski wrote:
> Is it possible to use the dune solvers to solve a linear system of 
> equations where A is a small (2x2 or 3x3) matrix of large sparse 
> matrices? I've created a matrix of type Dune::Matrix<  Dune::BCRSMatrix< 
> Dune::FieldMatrix<double, 1, 1> > >, but the program does not compile. 
> It seems that the type Dune::Matrix<T> is never thought to be used in 
> Dune::Preconditioner and Dune::InverseOperator. Is there another 
> matrix-type I can use for this purpose?
> 

The problem is that BCRSMatrix has no solve method. One has to set the
blocklevel of the preconditioners to l=2 instead of 1.

Markus