[petsc-users] SLEPc - Generalized symmetric eigenproblem using ARPACK

[Harshad Sahasrabudhe]

>
> With MUMPS you should not get spurious eigenvalues.

I get only a few spurious eigenvalues when using MUMPS with ARPACK, but the
eigenvectors are definitely wrong.

Did you try the krylovschur solver?

Yes, Krylov-Schur gives me correct results.

How do you know the eigenvalues are wrong?

I'm testing my implementation of Schrodinger equation solver with a 3D
harmonic oscillator potential. I'm getting correct results using FEAST and
krylovschur solvers.

Are you setting problem type to GHEP?

Yes



On Wed, Mar 25, 2015 at 4:37 PM, Jose E. Roman <jroman at dsic.upv.es> wrote:

>
> El 25/03/2015, a las 21:29, Harshad Sahasrabudhe escribió:
>
> > Hi,
> >
> > I'm trying to use the ARPACK interface in SLEPc for calculating smallest
> eigenvalues with eigenvectors of a generalized eigenproblem. The matrices
> are symmetric.
> >
> > What are the suggested linear solvers/preconditioners for this type of a
> system when using ARPACK? I am using shift and invert with a shift of 0.
> >
> > I get a lot of spurious eigenvalues when I use GMRES linear solver or
> MUMPS for LU factorization. Chebyshev doesn't seem to converge (I don't
> have a good guess for the higher end of eigenvalues).
> >
> > Thanks,
> > Harshad
>
> With MUMPS you should not get spurious eigenvalues. Did you try the
> krylovschur solver? How do you know the eigenvalues are wrong? Are you
> setting problem type to GHEP?
>
> Jose
>
>
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