On Thu, 13 Jun 2019 at 16:35, Alex Herbert <alex.d.herb...@gmail.com> wrote: > > > On 13/06/2019 15:59, Gary Gregory wrote: > > Now that RNG is up and going, it seems odd to still have: > > > > org.apache.commons.lang3.ArrayUtils.shuffle(double[], Random) > > > > Should we deprecate these APIs in favor of Commons RNG and if so which RNG > > APIs? > > > > Gary > Shuffling is in the commons-rng-sampling component. > > Shuffling for int[] primitive arrays is in the PermutationSampler [1]. > > Shuffling for a List<T> is in the ListSampler [2]. > > Currently there are methods to shuffle the entire length, or part of the > length starting from a position and shuffling to the start or end of the > array / list. > > There is no method for: > > - Shuffling a subsequence within the array / list defined by either > start and length or start and end. > > - Shuffling an array T[] > > - Shuffling primitive arrays other than int[] (This requires a bit of > work [3]) > > > [Lang] ArrayUtils only shuffles the full array but supports all > primitive array types and Object[]. It does not support a shuffle of T[]. > > So there is only partial overlap between the libraries. There is not a > like for like swap to deprecate ArrayUtils methods in favour of Commons > RNG methods. > > > I think it is quite a common use case to want to shuffle full length > arrays. I'm not sure about sub-sequence shuffles but one is a super-set > of the other. > > To deprecate ArrayUtils shuffle methods would require a new class in RNG > to support this for all primitives and a generic type T following this > prototype: > > ArrayUtils.shuffle(UniformRandomProvider rng, double[] data) > ArrayUtils.shuffle(UniformRandomProvider rng, double[] data, int start, > int length) > > > I'm not opposed to adding the methods to Commons RNG. Either in the > current sampling module or perhaps a new commons-rng-utils module > instead since a shuffle is not really a sample unless you use a > subsequence from the shuffled array.
Rather than shuffle etc in place, how about various iterators/selectors to return entries in randomised order? [Or does that already exist?] > > Alex > > > [1] > http://commons.apache.org/proper/commons-rng/commons-rng-sampling/javadocs/api-1.2/org/apache/commons/rng/sampling/PermutationSampler.html > > > [2] > http://commons.apache.org/proper/commons-rng/commons-rng-sampling/javadocs/api-1.2/org/apache/commons/rng/sampling/ListSampler.html > > [3] Supporting all the primitive avoids the currently usage to shuffle a > non-integer array which requires: > > - Clone the input array > - Shuffle a newly allocated int[] of ascending indices > - Use the shuffled indices to copy data from the clone back to the input > array > > This has unnecessary allocation overhead. > > > > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org > For additional commands, e-mail: dev-h...@commons.apache.org > --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
