Kent Thanks for the reply. I have started to have a look at the code to make the changes that you suggested, but must admit that I am a little lost.
I will continue to work on it, but any other tips would be greatly appreciated. Thanks Evan On Wed, Feb 4, 2009 at 10:50 PM, <[email protected]> wrote: > > Hi, > > Here are my rough thoughts on it. > > In FunctionSpace there is a function restriction which creates a > (restricted) DofMap based > on a mesh, a ufc:.dofmap and a MeshFunction. The way I have implemented, > this function is such that the MeshFunction contains booleans that > indicates which cells > that should be used in the DofMap. It could equally well be vertices or > other > mesh entities, but the way restriction is implemented now, it has to be > cells. > It should however be relatively easy to change it to other entities (I > think). > Changing this would give a loc2glob array which contains -1 for the entries > that should not be used. As I understand, petsc will then avoid these > entries > so it might work, at least for petsc, with only this alteration in the > function restriction. > > Kent > > > Hi > > > > Since I last rasied this issue there have been a lot of changes (great > > ones > > I must add) to the fenics codebase, so I thought I would ask again. > > > > I am interested in removing the rows and columns of the finite element > > matrices (for vector electromagnetic problems) associated with zero > valued > > Dirichlet boundary conditions. It is important that the original degrees > > of > > freedom (or a mapping between the two sets) be available so that the > > solution of a system of equations or an eigenvalue problem can be used to > > visualize the solution, for example. > > > > The removal of the degrees of freedom has two advantages that I can think > > of > > (for my applications at any rate). The first is that the systems being > > solved will be smaller. The second is of particular concern to me as I > am > > often solving eigenvalue problems and the unity eigenvalues that are > > introduce when applying the Dirichlet BCs in their current form > > contaminate > > the spectrum in many of my examples. > > > > Any thoughts or assistance would be greatly appreciated. > > > > Thanks > > Evan > > _______________________________________________ > > DOLFIN-dev mailing list > > [email protected] > > http://www.fenics.org/mailman/listinfo/dolfin-dev > > > > >
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