[dune-fem] Problems with dune-fem-howto tutorial

[Tobias Malkmus]

Hi Andrea

The howto code is quite old and outdated.

Next to the BiCGStab solver from dune-istl there is
the OEMBICGSTABOp which should work with the Dune::AdaptiveDiscreteFunction.

Try to use this solver type, it is defined in
dune/fem/solver/oemsolver/oemsolver.hh

Best Tobias

On 10/15/2013 06:39 PM, Sacconi, Andrea wrote:
> Hi everyone,
>
> I am playing with one of the tutorial programmes contained in dune-fem-howto.
> It's the well-known Poisson equation, but there is something that is puzzling me.
>
> Here are my questions:
> 1) if you modify the choice of the discrete function from Dune::AdaptiveDiscreteFunction to Dune::Fem::ISTLBlockVectorDiscreteFunction, is it necessary to modify Dune::Fem::SparseRowMatrixTraits with Dune::Fem::ISTLMatrixTraits for the matrix traits? The problem is, if I don't do that, I get a weird error with MatrixAdapter.
> 2) can we expect more or less the same amount of time spent on assembling the matrices? Because in the latter case, it seems that the assembling is 7 times slower than in the former case. How come?
> 3) I can't get the usual L2 and H1 orders of convergence anymore with Dune::Fem::ISTLBlockVectorDiscreteFunction and Dune::Fem::ISTLMatrixTraits. Where am I wrong?
>
> I need ISTL data structures since, afaik, it's the only one for which a BiCGStab iterative algorithm is available.
> I would really appreciate if you could shed some light on this matter!
>
> Thanks a lot in advance!
> Andrea
> __________________________________________________________
>
> Andrea Sacconi
> PhD student, Applied Mathematics
> AMMP Section, Department of Mathematics, Imperial College London,
> London SW7 2AZ, UK
> a.sacconi11 at imperial.ac.uk
>
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>


-- 
Tobias Malkmus                 <tomalk at mathematik.uni-freiburg.de>

Mathematisches Institut               Tel: +49 761 203 5627
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