[petsc-users] AMG using ML : Advanced monitoring

Matthew Knepley knepley at gmail.com
Fri May 11 19:48:25 CDT 2012

On Fri, May 11, 2012 at 8:20 PM, Karthik Duraisamy <dkarthik at stanford.edu>wrote:

> -mg_levels_4_ksp_type gmres -mg_levels_4_ksp_gmres_restart 300
> -mg_levels_4_ksp_gmres_max_it 300 -mg_levels_4_ksp_compute_eigenvalues
> -mg_levels_4_pc_type none
> Quick followup question - When solving Ax = b, I have an outer loop that
> keeps feeding the same A matrix to the KSP solver, but with different
> initial guesses for x. When doing this, I get slightly different eigenvalue
> estimates every time (minimum real part off by 10%). I just want to confirm
> that this is because of the iterative process.

Yes. A different initial residual means a different Krylov space


> Thanks

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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120511/0b528e1b/attachment.htm>

More information about the petsc-users mailing list