[petsc-users] question about CISS

[Povolotskyi, Mykhailo]

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.