how to get all the singular values of the matrix?

[Yujie]

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 at gmail.com> 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 at gmail.com> 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
>
>
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