On Fri, Aug 12, 2011 at 4:03 AM, Charanpal Dhanjal < [email protected]> wrote:
> Thank Nadav for testing out the matrix. I wonder if you had a chance to > check if the resulting decomposition contained NaN or Inf values? > > As far I understood, numpy.linalg.svd uses routines in LAPACK and ATLAS > (if available) to compute the corresponding SVD. I did some > complementary tests on Debian Squeeze on an Intel Xeon W3550 CPU and the > call to numpy.linalg.svd results in the LinAlgError "SVD did not > converge", however the test leading to results containing NaN values ran > on Debian Lenny on an Intel Core 2 Quad. In both of these situations we > use Python 2.7.1 and numpy 1.5.1 (without ATLAS), and so the reasons for > the differences seem to be OS or processor dependent. Any ideas? > > Charanpal > > Date: Thu, 11 Aug 2011 07:21:09 -0700 > From: Nadav Horesh <[email protected]> > Subject: Re: [Numpy-discussion] SVD does not converge on "clean" > matrix > To: Discussion of Numerical Python <[email protected]> > Message-ID: > > <26FC23E7C398A64083C980D16001012D246DFC5F90@VA3DIAXVS361.RED001.local> > Content-Type: text/plain; charset="us-ascii" > > > > Had no problem on a gentoo 64 bit machine using atlas 3.8.0 (Core I7, > > python 2.7.2, numpy versions1.60 and 1.6.1) > Another data point: on Mac OS X, with Python 2.7.2 and numpy 1.6.0 (using EPD 7.1), I get the error: $ ipython --pylab Enthought Python Distribution -- www.enthought.com Python 2.7.2 |EPD 7.1-1 (32-bit)| (default, Jul 3 2011, 15:40:35) Type "copyright", "credits" or "license" for more information. IPython 0.11.rc1 -- An enhanced Interactive Python. ? -> Introduction and overview of IPython's features. %quickref -> Quick reference. help -> Python's own help system. object? -> Details about 'object', use 'object??' for extra details. Welcome to pylab, a matplotlib-based Python environment [backend: WXAgg]. For more information, type 'help(pylab)'. In [1]: numpy.__version__ Out[1]: '1.6.0' In [2]: arr = load('matrix_leading_to_bad_SVD.npz')['arr_0'] In [3]: np.linalg.svd(arr) --------------------------------------------------------------------------- LinAlgError Traceback (most recent call last) /Users/warren/tmp/<ipython-input-3-e475bd6de739> in <module>() ----> 1 np.linalg.svd(arr) /Library/Frameworks/Python.framework/Versions/7.1/lib/python2.7/site-packages/numpy/linalg/linalg.py in svd(a, full_matrices, compute_uv) 1319 work, lwork, iwork, 0) 1320 if results['info'] > 0: -> 1321 raise LinAlgError, 'SVD did not converge' 1322 s = s.astype(_realType(result_t)) 1323 if compute_uv: LinAlgError: SVD did not converge Warren > > > > Nadav > > >On Thu, 11 Aug 2011 15:23:22 +0200, [email protected] > > wrote: > >> Hi all, > >> > >> I get an error message "numpy.linalg.linalg.LinAlgError: SVD did not > >> converge" when calling numpy.linalg.svd on a "clean" matrix of size > >> (1952, > >> 895). The matrix is clean in the sense that it contains no NaN or > >> Inf > >> values. The corresponding npz file is available here: > >> > >> > https://docs.google.com/leaf?id=0Bw0NXKxxc40jMWEyNTljMWUtMzBmNS00NGZmLThhZWUtY2I2MWU2MGZiNDgx&hl=fr > >> > >> Here is some information about my setup: I use Python 2.7.1 on > >> Ubuntu > >> 11.04 with numpy 1.6.1. Furthermore, I thought the problem might be > >> solved > >> by recompiling numpy with my local ATLAS library (version 3.8.3), > >> and this > >> didn't seem to help. On another machine with Python 2.7.1 and numpy > >> 1.5.1 > >> the SVD does converge however it contains 1 NaN singular value and 3 > >> negative singular values of the order -10^-1 (singular values should > >> always be non-negative). > >> > >> I also tried computing the SVD of the matrix using Octave 3.2.4 and > >> Matlab > >> 7.10.0.499 (R2010a) 64-bit (glnxa64) and there were no problems. Any > >> help > >> is greatly appreciated. > >> > >> Thanks in advance, > >> Charanpal > > _______________________________________________ > NumPy-Discussion mailing list > [email protected] > http://mail.scipy.org/mailman/listinfo/numpy-discussion >
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