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From Dimitri Pourbaix <pourb...@astro.ulb.ac.be>
Subject Re: [math] 2.1 Release plan
Date Sun, 14 Mar 2010 19:20:12 GMT
Luc,

> Concerning MATH-321, the partial fix I proposed has been withdrawn by
> the complete rewrite of SVD.
> This partial fix also was not considered mathematically sound by Dimitri
> since the dimensions of the matrices did not match complete SVD. Well,
> this was in fact desired as MATH-321 explicitly asks for non-full SVD.
>
> So I'm not sure anymore what we need to do. If we follow Dimitri's
> rationale, we should close this as WON'T FIX. If we decide to fix it, I
> think we should postpone it to after 2.1 to have time to decide how we
> solve it. SVD has already been vastly improved by Dimitri's work, so I
> would really much like to see it published now.
>
> Dim, what do you think about this ?

The version I uploaded does not benefit from any sparsity of the matrix
to be decomposed.  I have not looked at any algorithm for this kind of
matrix as it would likely involve a different way of storing the matrix
itself.  I agree to put "WON'T FIX" for 321 unless someone can come up
with an example showing that that, for a sparse matrix, the present
version does not return the right answer.

Dim.
----------------------------------------------------------------------------
Dimitri Pourbaix                         *
Institut d'Astronomie et d'Astrophysique *      Don't worry, be happy
CP 226, office 2.N4.211, building NO     *         and CARPE DIEM.
Universite Libre de Bruxelles            *
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  B-1050 Bruxelles                        *      Fax : +32-2-650.42.26
http://sb9.astro.ulb.ac.be/~pourbaix     * mailto:pourbaix@astro.ulb.ac.be

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