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MathGroup Archive 2004

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Re: Eigensystem: different solution in V5.0 and V4.1 ??

  • To: mathgroup at smc.vnet.net
  • Subject: [mg48311] Re: Eigensystem: different solution in V5.0 and V4.1 ??
  • From: ivo.bleylevens at facburfdaw.unimaas.nl (Ivo bleylevens)
  • Date: Sun, 23 May 2004 06:15:37 -0400 (EDT)
  • References: <c8mu5a$8nu$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hello again !
 
This is in addition to my message earlier.
 
I forgot to say (maybe the most important part of my message) that the
eigenvalues Mathematica 5.0 calculates, are the correct eigenvalues
when the notebook is ran at a AMD Athlon 1200 MHz or AMD Duron 800 MHz
PC and not on a Pentium4 2,6 GHz stand-alone machine and a Pentium4
3,06 HT notebook !!
 
So: Mathematica 5.0 produces only the right solutions of Eigensystem
when you don't use a Pentium 4 processor ???
 
Greetings
Ivo Bleylevens

ivo.bleylevens at facburfdaw.unimaas.nl (Ivo bleylevens) wrote in message news:<c8mu5a$8nu$1 at smc.vnet.net>...
> Hello all !
> 
> I am a dutch PhD student at the University of Maastricht and I have a
> question about some strange behaviour of the Mathematica's 5.0
> function Eigensystem[]. 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 ??
> 
> * I already tried to use the options of Eigensystem[] described at
> http://documents.wolfram.com/v5/Built-inFunctions/AdvancedDocumentation/LinearAlgebra/4.4.html
> but that also didn't help.
> 
> * I tried to set the precision of Mathematica 5.0 with the command
> eigsys = Eigensystem[N[M, 30]] but that didn't help either !
> 
> * I also calculated the eigenvalues of the matrix M with another system using
> the functions EIG and EIGS (which makes use op the LAPACK functions.
> Mathematica 5 uses this functions also as described in the link
> above). The eigenvalues computed with this two functions are exactly
> similar with the eigenvalues calculated in Mathematica 4.1....
> 
> So in my opinion Mathematica 5.0 produces incorrect
> eigenvalues......can someone help me ???
> 
> Ivo Bleylevens
> Universiy of Maastricht


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