[Numpy-discussion] Strategy for OpenBLAS

Nathaniel Smith njs at pobox.com
Wed May 27 04:13:04 EDT 2015

On Tue, May 26, 2015 at 9:53 AM, Julian Taylor
<jtaylor.debian at googlemail.com> wrote:
> On 05/26/2015 04:56 PM, Matthew Brett wrote:
>> Hi,
>> This morning I was wondering whether we ought to plan to devote some
>> resources to collaborating with the OpenBLAS team.
>> It is relatively easy to add tests using Python / numpy.  We like
>> tests.  Why don't we propose a collaboration with OpenBLAS where we
>> build and test numpy with every / most / some commits of OpenBLAS, and
>> try to make it easy for the OpenBLAS team to add tests.    Maybe we
>> can use and add to the list of machines on which OpenBLAS is tested
>> [1]?  We Berkeley Pythonistas can certainly add the machines at our
>> buildbot farm [2].  Maybe the Julia / R developers would be interested
>> to help too?
> Technically we only need a single machine with the newest instruction
> set available. All other cases could then be tested via a virtual
> machine that only exposes specific instruction sets (e.g. qemu which
> could technically also emulate stuff the host does not have).
> Concerning test generation there is a huge parameter space that needs
> testing due with openblas, at least some of it would need to be
> automated/fuzzed. We also need specific preconditioning of memory to
> test failure cases openblas had in the past, E.g. filling memory around
> the matrices with nans and also somehow filling openblas own temporary
> buffers with some signaling values (might require special built openblas
> if _MALLOC_PERTURB does not work).

A lot of this stuff is easier if we take a white-box instead of
black-box approach -- adding hooks in OpenBLAS to override the
CPU-based kernel-autoselection sounds a lot easier than creating
unnatural machines in qemu, and similarly for initializing temporary
buffers. (I would be really unsurprised if OpenBLAS re-uses temporary
buffers across calls instead of doing a free/re-malloc, for example.)

> Maybe it would be feasible to write a hypothesis [0] strategy for some
> of the blas stuff to automate the parameter exploration.

Or if this is daunting, you can get pretty far just sitting down and
writing some for loops... I think this is a case where something is a
lot better than nothing :-).


Nathaniel J. Smith -- http://vorpus.org

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