[Numpy-discussion] Numpy.linalg.eig oddity

David Goldsmith d.l.goldsmith@gmail....
Wed Jun 23 17:05:57 CDT 2010

On Wed, Jun 23, 2010 at 2:17 PM, Robert Kern <robert.kern@gmail.com> wrote:

> On Wed, Jun 23, 2010 at 13:25, Salim, Fadhley (CA-CIB)
> <fadhley.salim@ca-cib.com> wrote:
> > I've been investigating a truly bizarre bug related to the use of
> > numpy.linalg.eig.
> >
> > I have two classes which both use numpy.linalg.eig. These classes are
> > used at very different times and are not connected in any way other than
> > the fact that they both share this particular dependancy.
> >
> > I have found that whichever class is called second will produce a
> > slightly different answer if numpy.linalg.eig is used sometime earlier.
> > I've eliminated all other variables besides the call to eig(). This
> > seems completely implausible, and yet I have the data.
> >
> > As far as I am aware, eig() is wholly stateless and therefore using it
> > should not affect any subsequent calls to the function, right?
> >
> > Numpy==1.2.1, Scipy==0.7.0
> >
> > I've checked the bug-trac for this function and can find no references
> > to bugs which cause it to hold-state, even in the somewhat out of date
> > version of numpy. Can somebody let me know if there's something that I'm
> > missing.
> I don't think we've seen anything like that before. If you can come up
> with a small, self-contained script that demonstrates the problem, we
> will take a look at it.
> --
> Robert Kern

Of course providing what Robert requests would be optimal, but at the very
least/in the mean time, if you can provide "the data" you say you have, that
might also be helpful.

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