[Numpy-discussion] Backwards-incompatible improvements to numpy.random.RandomState
Sturla Molden
sturla.molden at gmail.com
Sun May 24 14:56:17 EDT 2015
On 24/05/15 20:04, Nathaniel Smith wrote:
> I'm not sure what you're envisioning as needing a deprecation cycle? The
> neat thing about random is that we already have a way for users to say
> that they want replicability -- the use of an explicit seed --
No, this is not sufficient for random numbers. Random sampling and
ziggurat generators are examples. If we introduce a change (e.g. a
bugfix) that will affect the number of calls to the entropy source, just
setting the seed will in general not be enough to ensure backwards
compatibility. That is e.g. the case with using ziggurat samplers
instead of the current transcendental transforms for normal, exponential
and gamma distributions. While ziggurat is faster (and to my knowledge)
more accurate, it will also make a different number of calls to the
entropy source, and hence the whole sequence will be affected, even if
you do set a random seed.
Sturla
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