[Trilinos-Users] trilinos diagonalization

[Alicia Klinvex]

Hello,

One of the nice things about Anasazi is that it is very easy to swap out
one solver for another in your driver, so if you wanted to, you could try
them all without changing your code very much.  My experience with LOBPCG
has been that if you aren't providing it with a good preconditioner, you're
going to have a bad time...so maybe someone could recommend an effective
preconditioner based on the characteristics you've mentioned.

Assuming your matrix is positive definite (meaning all of its eigenvalues
are positive), you can use any of the Anasazi eigensolvers.  I definitely
recommend trying TraceMin-Davidson, which is nice in that it doesn't
require accurate linear solves the way that many other eigensolvers do, and
it has a guaranteed rate of convergence given a certain set of parameters.
(Sidenote: TraceMin-Davidson was my thesis work, so I am certainly biased
toward it.  Also, it's currently marked experimental, so please let us know
if you encounter any unexpected behavior.)  RTR tends to work well on your
kind of problem too.  If you want to use Krylov-Schur, it will require a
couple of extra steps in your driver to run it in shift-and-invert mode; we
can discuss those steps if you're really interested in doing that, but
Krylov-Schur seems like overkill on your problem.

Best wishes,
Alicia

On Thu, Jul 9, 2015 at 8:33 AM, 임재창 <ljchang94 at kaist.ac.kr> wrote:

>  Dear Trilinos developers and users,
>
>
> I'm using Anasazi package to diagonalize matrices with Epetra_CrsMatrix.(Eigensolver is LOBPCG)
>
>
> My problem is that diagonalization sometimes not converged.
>
>
> The characteristics of the matrix  that i want to diagonalize are
>
>
> 1. diagonal dominent
>
>
> 2. symmetry
>
>
> 3. almost 80~90% of entries are zero
>
>
> 4. i want to know a few lowest eigenvalues
>
>
> are there any options which are efficient for diagonalizing these kinds of matrices?
>
>
> Best regards,
>
>
>
> jaechang lim
>
>
>
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