dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Mon, Sep 13, 2010 at 01:16:23PM +0200, kent-and@xxxxxxxxx wrote:
> > On 13. sep. 2010 08:11, Evan Lezar wrote:
> >> Question #125019 on DOLFIN changed:
> >> https://answers.launchpad.net/dolfin/+question/125019
> >>
> >>     Status: Answered => Open
> >>
> >> Evan Lezar is still having a problem:
> >> Hi
> >>
> >> I think Anders is correct. I have just had a look at the SystemAssembler
> >> code, and it does seem to also place ones on the diagonals of the matrix
> >> to which the boundary conditions are being applied. In addition, I am
> >> not solving a linear system, but eigenvalue problems and as such b is a
> >> Matrix not a Vector.
> >>
> >> At present I am manually removing the rows and columns for the matrices
> >> that correspond to (zero) Dirichlet conditions and then reconstructing
> >> the correct solution vector from the eigenvector that I obtain. This is
> >> fine for testing and getting the rest of the system running.
> >>
> >>
> >
> >
> > Is this really simpler than filtering the eigenpairs? As far as I see it
> >
> > (1) (As you know) the eigenvalues associated with the boundary
> > conditions are all 1's
>
> The eigenvalues will not only be 1. They will be 1, 2, 3, .. etc depending
> on then number
> of cells that meet. They should however be easy to spot and filter out.

Not if the problem solved is a model problem designed to give
eigenvalues that are 1, 2, 3 etc.

--
Anders