[SciPy-dev] Why does orth use svd instead of QR ?

Piotr Luszczek luszczek@eecs.utk....
Fri Feb 5 22:05:12 CST 2010


David Cournapeau <david <at> silveregg.co.jp> writes:

> 
> Gael Varoquaux wrote:
> > On Fri, Feb 05, 2010 at 04:18:02PM +0900, David Cournapeau wrote:
> >> So would be it ok to use this column-rotated QR in place of svd for 
> >> every case in orth ? I would have to check that QR with column rotation 
> >> is still significantly faster than svd, but I would surprised if if were 
> >> not the case. QR has also the advantage of being implemented in PLASMA 
> >> already contrary to eigen/svd solvers,
> > 
> > Out of curiosity, what's PLASMA, in this context?
> http://icl.cs.utk.edu/projectsfiles/plasma/html/README.html 
> It is under BSD license, and as a bonus point, may be compiled easily on 
> windows (MS is one of the sponsor of the project). The main drawback I 
> can see is that it requires a serial BLAS, and ATLAS cannot be switched 
> dynamically between serial and parallel (you have to relink).
> 
> I am hoping to provide a basic set of wrappers for scipy,

We (PLASMA team) are looking into this problem. In principle
it should be possible to just use parallel ATLAS and call
internal functions of ATLAS to get at the serial interface.
We might add this feature to PLASMA some time soon.

Piotr





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