[petsc-users] Multiple solves with PCMG fail

[Mark Adams]

On Mon, Oct 27, 2014 at 3:02 PM, Filippo Leonardi <
filippo.leonardi at sam.math.ethz.ch> wrote:

> On Monday 27 October 2014 14:31:45 Mark Adams wrote:
> >
> > I'm not sure what you are asking.  starting i=0 or i=1, and with and
> > without mg.  So four possibilities?  The solutions will be different for
> > i=0 or 1 in this code:
> >
>
> Yes, 4 cases:
> i = 0, MG: wrong solution *(for *any* solution, even afterwards, i.e. i >=
> 0)*
> (and error, if debug)
>

OK, so the first time there is no RHS and so not eigen estimate and the
next solves do not check to see if a valid eigen estimate has been created.

Jed: could we just check for zero iterations in the eigen estimator and
then call the random thing.  Or something along those lines.



> i = 1, MG: ok
> i = 0, CG: (or anything): ok
> i = 1, CG (or anything): ok
>
> > -ksp_chebyshev_estimate_eigenvalues_random
>
> Can try this but the problem, to me, seems deeper (because inherited from
> each
> solve afterwards).
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