[Numpy-discussion] NEP: Random Number Generator Policy

Robert Kern robert.kern at gmail.com
Sun Jun 3 20:36:58 EDT 2018

On Sun, Jun 3, 2018 at 4:35 PM Eric Wieser <wieser.eric+numpy at gmail.com>

> You make a bunch of good points refuting reproducible research as an
> argument for not changing the random number streams.
> However, there’s a second use-case you don’t address - unit tests. For
> better or worse, downstream, or even our own
> <https://github.com/numpy/numpy/blob/c4813a9/numpy/core/tests/test_multiarray.py#L5093-L5108>,
> unit tests use a seeded random number generator as a shorthand to produce
> some arbirary array, and then hard-code the expected output in their tests.
> Breaking stream compatibility will break these tests.
By the way, the reason that I didn't mention this use case as a motivation
in the Status Quo section because, as I reviewed my mail archive, this
wasn't actually a motivating use case for the policy. It's certainly a use
case that developed once we did make these (*cough*extravagant*cough*)
guarantees, though, as people started to rely on it, and I hope that my
StableRandom proposal addresses it to your satisfaction. I could add some
more details about that history if you think it would be useful.

Robert Kern
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