On Fri, Feb 12, 2016 at 3:12 PM, Andrew Barnert via Python-Dev
<python-dev@python.org> wrote:
> On Thursday, February 11, 2016 7:20 PM, Stephen J. Turnbull
> <step...@xemacs.org> wrote:
>
>
>
>> I think we should keep it around forever. Even my slowest colleagues
>> are learning that they should record their seeds and PRNG algorithms
>> for reproducibility's sake. :-)
>
> +1
>
>> For that matter, restore Wichmann-Hill.
>
> So you can write code that works on 2.3 and 3.6, but not 3.5?
>
> I agree that it shouldn't have gone away, but I think it may be too late for
> adding it back to help too much.
You're probably right, but the point isn't to make the same code run,
necessarily. It's to make things verifiable. Suppose I do some
scientific research that involves a pseudo-random number component,
and I publish my results ("Monte Carlo analysis produced these
results, blah blah, using this seed, etc, etc"). If you want to come
back later and say "I think there was a bug in your code", you need to
be able to generate the exact same PRNG sequence. I published my
algorithm and my seed, so you should in theory be able to recreate
that sequence; but if you have to reimplement the same algorithm,
that's a lot of unnecessary work that could have been replaced with
"from random.deprecated_generators import WichmannHill as Random".
(Plus there's the whole question of "was your reimplemented PRNG
buggy" - or, for that matter, "was the original PRNG buggy". Using the
exact same code eliminates even that.)
So I'm +1 on keeping Mersenne Twister even after it's been replaced as
the default PRNG, -0 on reinstating something that hasn't been used in
well over a decade, and -1 on replacing MT today - I'm not seeing
strong arguments in favour of changing.
ChrisA
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