[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

Thanks very much for any help,

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