dolfin team mailing list archive

[Marie Rognes <meg@xxxxxxxxx>]

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
(2) The eigenvectors associated with these only have non-zero
coefficients for the relevant boundary degrees of freedom -- hence can
be filtered by examining the coefficients
(3) The krylov-schur solver in SLEPc 3.1(-p2) converges way more often
than before. This makes solving non-tiny singular, generalized
eigenvalue problems way easier.

--
Marie