[Dune] ISTL

[Peter Bastian]

Hello all,

I think you can safely use ISTL now.

What's implemented:
- small dense blocks, block compressed row storage with fixed size   blocks
- preconditioners: Jacobi, Gauss-Seidel, SOR, SSOR, ILU(0), ILU(n)
- solvers: Loop, CG, BiCGStab

What is not implemented yet:
- block compressed row matrix with variable sized (dense) blocks. This 
would be needed for hp-DG (since nobody has done that yet, its OK)
- avoiding operator[] in case of 1x1 blocks: I've included classes 
K1Vector and K11Matrix which can do that but they are not yet complete
- GMRES: has to be copied from SUMO and adapted
- Parallel support (distributed index sets and communication), Markus is 
currently working on that
- Parallel AMG preconditioner: Markus is working on that
- Some Benchmarking
- Writing the documentation in istl/doc


In order to use it you can look at the function test_Interface in 
istl/tutorial. It sets up a simple matrix and uses various solvers to 
solve a linear system.

There are still problems with optimization. icc with option 
-march=pentium4 yields code that is a factor 3 faster (scalar matrix, 
Gauss-Seidel preconditioner) than compiled with g++-3.4. Let's hope that 
gcc 4.0 is better ...

Have fun :-)

-- Peter