On 27 September 2016 at 12:22, Gilles <gil...@harfang.homelinux.org> wrote:
> Hi.
>
> On Tue, 27 Sep 2016 12:53:33 +0200, Emmanuel Bourg wrote:
>>
>> Le 27/09/2016 à 01:14, Gilles a écrit :
>>
>>>>> * Shuffling algorithm (cf. Commons Math's "o.a.c.m.MathArrays"),
>>>>
>>>>
>>>> This should go in the ArrayUtils class of commons-lang, with a
>>>> java.util.Random parameter.
>>>
>>>
>>> I don't get that.
>>> The idea is to parameterize the utilities with a "UniformRandomProvider"
>>> instance.
>>
>>
>> My suggestion is to add two methods to ArrayUtils in commons-lang for
>> each primitive type and Object (and maybe a couple more if we want to
>> shuffle only a subset of the array):
>>
>> ArraysUtils.shuffle(Object[] array)
>> ArraysUtils.shuffle(Object[] array, java.util.Random rnd)
>
>
> I (strongly) suggest
>
> ArraysUtils.shuffle(Object[] array, o.a.c.rng.UniformRandomProvider rnd)
Huh?
That would require LANG to depend on RNG.
I am against that.
>>
>> And if we want to shuffle with a random generator from commons-rng, we
>> simply convert the UniformRandomProvider into a java.util.Random using
>> the adapter:
>>
>> RandomProvider rng = RandomSource.create(...);
>> ArraysUtils.shuffle(array, new JDKRandomAdapter(rng));
>>
>> or
>>
>> RandomProvider rng = RandomSource.create(...);
>> ArraysUtils.shuffle(array, rng.asRandom());
>
>
> Similarly, we'd rather overload "shuffle" as follows
>
> ArraysUtils.shuffle(Object[] array, java.util.Random rnd) {
> shuffle(array, RandomUtils.asUniformRandomProvider(rnd));
> }
>
> where "RandomUtils" is currently in CM (package "o.a.c.math4.random").
>
> It is not a matter of taste (cf. caveat in "o.a.c.math4.random.RngAdpator").
> The factory method "asUniformRandomProvider" creates an instance that
> redirects all the interface methods to their counterpart in "Random" (when
> they exist): sequence of any type is the same, whether the Random instance
> is wrapped or not. "RngAdapter" however creates a "Random" instance where
> only 32-bits integers sequences are preserved.
>
> Moreover, the default RNG should be a good one, i.e. not "java.util.Random".
>
> But overall it would be much better to put all this in a new component
> and deprecate all of CL's "Random"-parameterized methods.
> It was noted (not only by me) that CL grew too big (and out of its original
> scope). "RandomUtils" is relatively small (in Lang 3.4): now is a good
> opportunity to deprecate these few methods and those intended for 3.5
> and redirect users to a dedicated component.
+1
>
> Gilles
>
>
>> Emmanuel Bourg
>>
>>
>
>
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