[dune-fem] Dune::Fem::GeoGridPart vs. Dune::GeometryGrid

[Sacconi, Andrea]

Hi everyone,

I would like to ask you a question about the difference between Dune::Fem::GeoGridPart and Dune::GeometryGrid.
>From what I have understood so far, the former wraps only the leaf level, while the latter keeps track of the entire hierarchy of the grid over which you perform your numerical simulations.

I am trying to modify my code to get a Dune::Fem::GeoGridPart working, but it doesn't. I mean, I am trying to use the same Dune::DiscreteCoordFunction I have already defined for using with Dune::GeometryGrid, but the compiler still complains.
My idea was to use a Dune::DiscreteCoordFunction which stores the vertices (as a P1 Lagrange function), and to write a method that modifies the DoFs of that function appropriately. Is this a good idea?
Which properties need to be satisfied by Dune::DiscreteCoordFunction ???

By the way, using Dune::GeometryGrid I observed a huge slow down (50 times slower than the case without wrapper) in the assembling of the matrices; I guess it is due to the necessity of converting iterators and so on, internally done by the wrapper. Could Dune::Fem::GeoGridPart speed up the process? Has anyone observed such a tremendous overhead?

Thank you very much!
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