[petsc-users] AMG using ML : Advanced monitoring

[Matthew Knepley]

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

   Matt


> 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
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