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https://issues.apache.org/jira/browse/RNG-62?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16695990#comment-16695990
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Gilles commented on RNG-62:
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Are the accessors {{getK()}} and {{getN()}} necessary?
> CombinationSampler
> ------------------
>
> Key: RNG-62
> URL: https://issues.apache.org/jira/browse/RNG-62
> Project: Commons RNG
> Issue Type: New Feature
> Reporter: Alex D Herbert
> Priority: Minor
>
> The sampling module contains a PermutationSampler. There is scope to create a
> CombinationSampler too.
> [https://en.wikipedia.org/wiki/Permutation]
> [https://en.wikipedia.org/wiki/Combination]
> If the order of the returned sample is not important then a combination can
> be generated faster than a permutation.
> The sample can be optimised by only performing the first k or (n-k) steps
> from a full Fisher-Yates shuffle from the end of the domain to the start. The
> upper positions will then contain a random permutation sample from the
> domain. The lower half is then by definition also a random sample (just not
> in a random order). The sample is then picked using the upper or lower half
> depending which makes the number of steps smaller.
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