[Dune] parallel solvers convergence

[Kirill Volyanskiy]

Hello

I have a problem with convergence in parallel mode.
I've taken the pdelab tutorial06 and added ALUGrid for dim=3,
Dune::PDELab::NonoverlappingConformingDirichletConstraints,
Dune::PDELab::ISTLBackend_NOVLP_BCGS_SSORk.

When I run it in monothread mode (mpirun -np 1 ./tutorial06), the
convergence is good.
When I run it in multithread mode (mpirun -np 5 ./tutorial06), there is
almost no convergence or it is extremely slow.
I tried various nonoverlapping parallel solvers as described in
pdelab-howto-article.pdf but no improvement.

Could you tell me what can be wrong?

Best
Kirill
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