[petsc-users] question about CISS

[Matthew Knepley]

On Thu, Aug 29, 2019 at 4:29 PM Jed Brown via petsc-users <
petsc-users at mcs.anl.gov> wrote:

> Elemental also has distributed-memory eigensolvers that should be at
> least as good as ScaLAPACK's.  There is support for Elemental in PETSc,
> but not yet in SLEPc.
>

Also if its symmetric, isn't https://elpa.mpcdf.mpg.de/ fairly scalable?

   Matt


> "Povolotskyi, Mykhailo via petsc-users" <petsc-users at mcs.anl.gov> writes:
>
> > Thank you for suggestion.
> >
> > Is it interfaced to SLEPC?
> >
> >
> > On 08/29/2019 04:14 PM, Jose E. Roman wrote:
> >> I am not an expert in contour integral eigensolvers. I think
> difficulties come with corners, so ellipses are the best choice. I don't
> think ring regions are relevant here.
> >>
> >> Have you considered using ScaLAPACK. Some time ago we were able to
> address problems of size up to 400k   https://doi.org/10.1017/jfm.2016.208
> >>
> >> Jose
> >>
> >>
> >>> El 29 ago 2019, a las 21:55, Povolotskyi, Mykhailo <
> mpovolot at purdue.edu> escribió:
> >>>
> >>> Thank you, Jose,
> >>>
> >>> what about rings? Are they better than rectangles?
> >>>
> >>> Michael.
> >>>
> >>>
> >>> On 08/29/2019 03:44 PM, Jose E. Roman wrote:
> >>>> The CISS solver is supposed to estimate the number of eigenvalues
> contained in the contour. My impression is that the estimation is less
> accurate in case of rectangular contours, compared to elliptic ones. But of
> course, with ellipses it is not possible to fully cover the complex plane
> unless there is some overlap.
> >>>>
> >>>> Jose
> >>>>
> >>>>
> >>>>> El 29 ago 2019, a las 20:56, Povolotskyi, Mykhailo via petsc-users <
> petsc-users at mcs.anl.gov> escribió:
> >>>>>
> >>>>> Hello everyone,
> >>>>>
> >>>>> this is a question about  SLEPc.
> >>>>>
> >>>>> The problem that I need to solve is as follows.
> >>>>>
> >>>>> I have a matrix and I need a full spectrum of it (both eigenvalues
> and
> >>>>> eigenvectors).
> >>>>>
> >>>>> The regular way is to use Lapack, but it is slow. I decided to try
> the
> >>>>> following:
> >>>>>
> >>>>> a) compute the bounds of the spectrum using Krylov Schur approach.
> >>>>>
> >>>>> b) divide the complex eigenvalue plane into rectangular areas, then
> >>>>> apply CISS to each area in parallel.
> >>>>>
> >>>>> However, I found that the solver is missing some eigenvalues, even
> if my
> >>>>> rectangles cover the whole spectral area.
> >>>>>
> >>>>> My question: can this approach work in principle? If yes, how one can
> >>>>> set-up CISS solver to not loose the eigenvalues?
> >>>>>
> >>>>> Thank you,
> >>>>>
> >>>>> Michael.
> >>>>>
>


-- 
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

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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