[Numpy-discussion] Segfault with QR Decomposition

Charles R Harris charlesr.harris at gmail.com
Wed Oct 9 10:40:54 EDT 2013

On Wed, Oct 9, 2013 at 8:04 AM, Charanpal Dhanjal <charanpal at gmail.com>wrote:

> 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?
Works fine here with '1.9.0.dev-7457f15' linked against ATLAS. I suspect
problem is in OpenBLAS. What architecture/os do the two machines have? Is
OpenBLAS using more than one core?

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