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From: | David Bateman |
Subject: | Re: native eigs versus arpack eigs |
Date: | Thu, 30 Oct 2008 14:27:18 +0100 |
User-agent: | Mozilla-Thunderbird 2.0.0.16 (X11/20080724) |
brendan detracey wrote:
As Soren said, eigs is only available through the ARPACK package. So I presume you meant eigs versus eig. The eigs command uses an iterative Arnoldi approach to calculate a small subset of the eigenvalue/eigenvectors. This subset can either be the larger/smaller eigenvalues, or the eigenvalues that are closest to a particular value. However the eig command calculates all of the eigenvalues/eigenvectors of a matrix directly with a Hessenberg decomposition. The advantage of the eigs command is that it is that it isw ell suited for use with large sparse matrices, and is more rapid than eig when a small subset of eigenvectors/eigenvalues are needed. The disadvantage is that eigs, being an iterative approach, can have some stability issues, particularly if you specify a value of lambda that is exactly an eigenvalue.Hello, Finally got Octave compiled on CentOs 5.2 x86_64, thanks to help from this mailing list. Did not bother with "experimental" 64-bit compile, yet. 1) Now I wonder, what is the difference between the eigs command in the ARPACK interface vs. the native eigs command? Is it worth the bother?
The advantage of eig is that it gives all eigenvalues at the same time has better stability properties than eigs. Whereas its disadvantage is that there is no sparse version.
As Soren says "display" is a function that is used of OOP and so is only available in recent developmental versions of Octave. Do you mean you need OOP?2) I can't for the life of me find the Octave equivalent of the Matlab command "display"
D. -- David Bateman address@hiddenMotorola 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) The information contained in this communication has been classified as: [x] General Business Information [ ] Motorola Internal Use Only [ ] Motorola Confidential Proprietary
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