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MathGroup Archive 2004

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Re: Eigensystem: different solution in V5.0 and V4.1 [SOLVED: BUG in 5.0]

  • To: mathgroup at
  • Subject: [mg48407] Re: Eigensystem: different solution in V5.0 and V4.1 [SOLVED: BUG in 5.0]
  • From: Marcus Stollsteimer <marcus314 at>
  • Date: Fri, 28 May 2004 00:50:38 -0400 (EDT)
  • References: <c8mu5a$8nu$>
  • Sender: owner-wri-mathgroup at

Ivo bleylevens wrote:
> I have an 512x512 non-symmetric complex matrix M.
> When i use the command eigsys = Eigensystem[M] in Mathematica 5.0,
> the eigenvalues were not the eigenvalues I expected ! I calculated
> exactly the same notebook in Mathematica version 4.1 and these
> eigenvalues look the same as the wanted eigenvalues !! Am i doing
> something wrong in version 5.0 ??

Hello Ivo,

I evaluated your notebook both in Mathematica versions 5.0 and 5.0.1,
and here are the results:

5.0      wrong eigenvalues
5.0.1    correct result

It clearly *is* a bug in the 5.0 version.
As I already mentioned, we had a similar problem
with complex hermitian matrices bigger than 256x256.
The bug seems only to affect complex matrices,
there was no problem with eigenvalues of real matrices.


technical data:

OS:        Fedora Core release 1
Kernel:    2.4.22-1.2149.nptl
CPU:       Intel(R) Pentium(R) 4 CPU 2.66GHz

Am I my brother's keeper? Yes. Interestingly, in my case I share
that honor with the Prospect Park Zoo. -- W. Allen

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