[Numpy-discussion] Backwards-incompatible improvements to numpy.random.RandomState

[josef.pktd at gmail.com]

On Sun, May 24, 2015 at 5:09 PM, Antony Lee <antony.lee at berkeley.edu> wrote:

> 2015-05-24 13:30 GMT-07:00 Sturla Molden <sturla.molden at gmail.com>:
>
>> On 24/05/15 10:22, Antony Lee wrote:
>>
>> > Comments, and help for writing tests (in particular to make sure
>> > backwards compatibility is maintained) are welcome.
>>
>> I have one comment, and that is what makes random numbers so special?
>> This applies to the rest of NumPy too, fixing a bug can sometimes change
>> the output of a function.
>>
>> Personally I think we should only make guarantees about the data types,
>> array shapes, and things like that, but not about the values. Those who
>> need a particular version of NumPy for exact reproducibility should
>> install the version of Python and NumPy they need. That is why virtual
>> environments exist.
>
>
> I personally agree with this point of view (see original discussion in
> #5299, for example); if it was only up to me at least I'd make
> RandomState(seed) default to the latest version rather than the original
> one (whether to keep the old versions around is another question).  On the
> other hand, I see that this long-standing debate has prevented obvious
> improvements from being added sometimes for years (e.g. a patch for
> Ziggurat normal variates has been lying around since 2010), or led to
> potential API duplication in order to fix some clearly undesirable behavior
> (dirichlet returning "nan" being described as "in a strict sense not really
> a bug"(!)), so I'm willing to compromise to get this moving forward.
>


It's clearly a different kind of "bug" than some of the ones we fixed in
the past without backwards compatibility discussion where the distribution
was wrong, i.e. some values shifted so parts have more weight and parts
have less weight.

As I mentioned, I don't see any real problem with the proposal.

Josef



>
> Antony
>
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