[Numpy-discussion] NEP: Random Number Generator Policy

[Robert Kern]

On Sun, Jun 3, 2018 at 10:27 PM <josef.pktd at gmail.com> wrote:

>
>
> On Mon, Jun 4, 2018 at 12:53 AM, Stephan Hoyer <shoyer at gmail.com> wrote:
>
>> On Sun, Jun 3, 2018 at 8:22 PM Ralf Gommers <ralf.gommers at gmail.com>
>> wrote:
>>
>>> It may be worth having a look at test suites for scipy, statsmodels,
>>> scikit-learn, etc. and estimate how much work this NEP causes those
>>> projects. If the devs of those packages are forced to do large scale
>>> migrations from RandomState to StableState, then why not instead keep
>>> RandomState and just add a new API next to it?
>>>
>>
>> Tests that explicitly create RandomState objects would not be difficult
>> to migrate. The goal of "StableState" is that it could be used directly in
>> cases where RandomState is current used in tests, so I would guess that
>> "RandomState" could be almost mechanistically replaced by "StableState".
>>
>> The challenging case are calls to np.random.seed(). If no replacement API
>> is planned, then these would need to be manually converted to use
>> StableState instead. This is probably not too onerous (and is a good
>> cleanup to do anyways) but it would be a bit of work.
>>
>
> I agree with this. Statsmodels uses mostly np.random.seed. That cleanup is
> planned, but postponed so far as not high priority. We will have to do it
> eventually.
>
> The main work will come when StableState doesn't include specific
> distribution, Poisson, NegativeBinomial, Gamma, ... and distributions that
> we don't even use yet, like Beta.
>

I would posit that it is probably very rare that one uses the full breadth
of distributions in unit tests. You may be the only one. :-)


> I don't want to migrate random number generation for the distributions
> abandoned by numpy Stable to statsmodels.
>

What if we followed Kevin's suggestion and forked off RandomState into its
own forever-frozen package sooner rather than later? It's intended use
would be for people with legacy packages that cannot upgrade (other than
changing some imports) and for unit tests that require precise streams for
a full breadth of distributions. We would still leave it in numpy.random
for a deprecation period, but maybe we would be noisy about it sooner and
remove it sooner than my NEP planned for.

Would that work? I'd be happy to maintain that forked-RandomState for you.

I would probably still encourage most people to continue to use
StableRandom for most unit testing.

-- 
Robert Kern
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