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Re: Good eigenvalue/eigenvector test problems for eigs?

From: Sebastien Loisel
Subject: Re: Good eigenvalue/eigenvector test problems for eigs?
Date: Fri, 22 Sep 2006 13:49:27 -0400

The SVD of that SPD matrix is actually nice. Since it's SPD, its SVD is simply its diagonalization (A=U'DU). The eigenvectors U are various frequencies of sin and the eigenvalues D are precisely the eigenvalues of the second derivative operator, shifted and scaled into [2,6].

On 9/22/06, David Bateman <address@hidden> wrote:
Sebastien Loisel wrote:
> Or maybe you mean it's got double eigenvalues all over the place?
The svd of it is pretty ugly, but I don't really see why the doubled
eigenvalues should be an issue.. The rooser matrix also has this sort of
problem and I can get that to work fine. In any case, I'm now using the
wilkinson function to generate test matrices, and have eigs fully
working for real symmetric and non-symmetric problems. I still have an
issue with convergence of complex eigenvalues, that seems to be a bug in
my code as both FreeMat and matlab do not display the same behavior.
Give me a few days and I should be able to release a working version of


David Bateman                                address@hidden
Motorola Labs - Paris                        +33 1 69 35 48 04 (Ph)
Parc Les Algorithmes, Commune de St Aubin    +33 6 72 01 06 33 (Mob)
91193 Gif-Sur-Yvette FRANCE                  +33 1 69 35 77 01 (Fax)

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