[Numpy-discussion] Zero row in SVD's unitary matrix on some Mac's
Rob Beezer
beezer at ups.edu
Tue Apr 26 14:58:07 EDT 2011
On 04/26/2011 11:25 AM, Pauli Virtanen wrote:
> I think it is worth testing if this change fixes it. Note that current
> LAPACK docs have the number 7 there instead of 5, so there may really be
> a bug here.
It appears to me the problem is more subtle than just a strict comparison
between the number of rows and the number of columns.
http://trac.sagemath.org/sage_trac/attachment/ticket/11248/broken.png
shows a plot of matrix sizes (number of rows on the horizontal, number of
columns on vertical). This is on an OSX 10.5 machine and whereever there is a
dot then the SVD seems to *always* produce a non-unitary V, and the absence of a
dot indicates no failures were found. So maybe a workspace size could be the
culprit?
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