[petsc-users] ML spectral radius estimate

[Matthew Knepley]

On Wed, Jun 22, 2011 at 10:37 AM, John Mousel <john.mousel at gmail.com> wrote:

> I'm using ML as a preconditioner, and I want to get an estimate of the
> spectral radius of my preconditioned matrix. I see a flag
> -pc_ml_SpectralNormScheme_Anorm. Does this need to be set in conjunction
> with another flag like -ksp_compute_eigenvalues or something cool I don't
> know about?


I do not see a way to pull out the estimate from ML. However, you can easily
replicate their estimate using

  -ksp_monitor_singular_values

and run GMRES with -pc_type none. If you run with ML, it will estimate the
extreme values for the preconditioned operators.

   Matt


>
> John
>



-- 
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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