[Numpy-discussion] Segfault with QR Decomposition

Charanpal Dhanjal charanpal at gmail.com
Wed Oct 9 10:04:09 EDT 2013


I get a segmentation fault upon running the following:

import numpy
A = numpy.ones((7000000, 8))
Q, R = numpy.linalg.qr(A)

on Python 2.7.3, Linux 64-bit using numpy 1.9.0.dev-ec3603f linked
against OpenBLAS. If A is a smaller matrix then the QR decomposition
works (for example A has shape (4000000, 8)). I haven't quite narrowed
down the exact threshold where the crash occurs, however I know that the
above A is 448 MB (Q and R are no bigger), and the machine in question
has 32GB of RAM. I also tested scipy.linalg.qr (version
0.14.0.dev-ced994c) with the same results.

I don't get the same problem on my laptop which is Python 2.7.3, Linux
64-bit but with numpy 1.8.0rc1 linked to OpenBLAS. Both machines have
OpenBLAS 0.2.6. Does anyone have some insight into why this problem is
occuring?

Thanks very much for any help,
Charanpal



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