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Re: Sparse-merge


From: David Bateman
Subject: Re: Sparse-merge
Date: Thu, 10 Mar 2005 09:37:18 +0100
User-agent: Mozilla Thunderbird 0.8 (X11/20040923)

Richard Hindmarsh wrote:



David Bateman wrote:

John W. Eaton wrote:



| Thanks. Will 2.9.x (or does the main trunk) have an interface to ARPACK | (e.g. through "eigs"), or is anyone working on this?

Not yet.  SEe the list of projects for sparse matrices in the file

http://www.octave.org/cgi-bin/viewcvs.cgi/octave/PROJECTS?rev=1.60&view=auto



ARPACK is definitely on the todo list. It is a complete lack of time at the moment that will prevent me from doing something here.


If you want to do the ARPACK interfacing, I'd welcome the help and would be willing to vet the code and give pointers.

I could possibly do it - I used ARPACK before "eigs" appeared in Matlab and have written .mex files though not .oct. Am motivated but short of time.

A quick look at "eigs" in Matlab shows that "eigs.m" calls an interface routine called "arpackc.dll" (or whatever suffix). It also looks as though "eigs" would be largely useable in Octave. I guess that an Octave "arpackc" would not be too difficult to write but what is then one expected to do - rewrite "eigs" so that it doesn't look like the Matlab one?


Richard,

I have to agree with John on this, you can't use any matlab code whatsoever, at the risk of being accused of copyright violation.... I consider the help available on the mathworks website as open game for developing compatiability code, at least in terms of a specification of the interface, but again don't copy it when you write the help for the functions.

I also consider that cross-comparison of the outputs for octave and matlab implementations is fair game. However, I never look at the matlab dot-m files at the risk of finding myself writing the same code even accidentally. This makes life slightly harder of course...

ARPACK is needed for the eigs function and the svds function, and would then be interfaced to the rank, etc functions to allow them to work. This shouldn't be a major development for a person familar with ARPACK and oct-files. The main issue would be one of packaging, the way John is leaning I think he would expect ARPACK to be an external library with an autoconf function to detect its presence. Then the eigs.cc and svds.cc code would link to this library if present or build a stub version that throws an error.

In any case, we'd welcome any inputs, and I would give pointers once you start..

Regards
David

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

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