[Numpy-discussion] Strategy for OpenBLAS

Julian Taylor jtaylor.debian at googlemail.com
Tue May 26 12:53:08 EDT 2015

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).

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

And then we'd need to run everything under valgrind as due to the
assembler implementation of openblas we can't use the faster address
sanitizers gcc and clang now provide.

[0] https://hypothesis.readthedocs.org/en/latest/

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