[Speed] External sources of noise changing call_simple "performance"

[Armin Rigo]

Hi Victor,

On 17 May 2016 at 23:11, Victor Stinner <victor.stinner at gmail.com> wrote:
> with PYTHONHASHSEED=1 to test the same hash function. A more generic
> solution is to use multiple processes to test multiple hash seeds to
> get a better uniform distribution.

What you say in the rest of the mail just shows that this "generic
solution" should be applied not only to PYTHONHASHSEED, but also to
other variables that seem to introduce deterministic noise.  You've
just found three more: the locale, the size of the command line, and
the working directory.  I guess the mere size of the environment also
plays a role.  So I guess, ideally, you'd run a large number of times
with random values in all these parameters.  (In practice it might be
enough to run a smaller fixed number of times with known values in the
parameters.)


A bientôt,

Armin.