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 >> <[email protected]> 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. >>
