Re: how to get all the singular values of the matrix?

[Hong Zhang <hzhang@xxxxxxxxxxx>]

If you want few selected eigen solutions of sparse matrix,
you should use sparse eigen solver. Take a look at'
slepc (http://www.grycap.upv.es/slepc/)
or use slepc interface with arpack.

Hong


On Mon, 14 Jan 2008, Yujie wrote:

> Thank you for your advice.
> I have used -ksp_compute_eigenvalues_explicitly to get the eigen values.
> However, it is very very
> slow because the dimension of the matrix is about ten thousand.
>
> Yujie
>
> On 1/14/08, Matthew Knepley <knepley@xxxxxxxxx> wrote:
> > You can use
> >
> >
> > http://www-unix.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/KSP/KSPComputeEigenvaluesExplicitly.html
> >
> > with and without a preconditioner. We have not coded the SVD
> > counterpart, but you can use
> >
> >
> > http://www-unix.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/KSP/KSPComputeExplicitOperator.html
> >
> > and then call the LAPACK yourself.
> >
> >   Matt
> >
> > On Jan 13, 2008 11:23 PM, Yujie <recrusader@xxxxxxxxx> wrote:
> > > Hi, everyone
> > >
> > > I want to select iterative methods by observing the singular values
> > > decompostion of the matrix. However, I don't know how to get all the
> > > singular values of the matrix in PETSc. I know the command
> > > "-ksp_monitor_singular_value" may get the max and min singular values at
> > > each iteration. How to get the singular values of the matrix I want to
> > > solve? In addition, when I use the preconditioned iterative method, how
> > to
> > > get the singular values of the preconditioned iterative operator?
> > >
> > > thanks a lot.
> > >
> > > Regards,
> > > Yujie
> >
> >
> >
> > --
> > What most experimenters take for granted before they begin their
> > experiments is infinitely more interesting than any results to which
> > their experiments lead.
> > -- Norbert Wiener