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https://issues.apache.org/jira/browse/MATH-1370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16341076#comment-16341076
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Gilles commented on MATH-1370:
------------------------------
An issue that got lost in the long-standing discussions about the future of
"Commons Math".
I seem to have redone the same changes that were proposed here while porting
some of the functionality to "Commons RNG" (cf. RNG-47)! :(
Those modifications should still be applied to class {{EnumeratedDistribution}}
(but the branch is badly out-of-date after implementing changes proposed in
STATISTICS-2.
> Increase efficiency of EnumeratedDistribution#probability
> ---------------------------------------------------------
>
> Key: MATH-1370
> URL: https://issues.apache.org/jira/browse/MATH-1370
> Project: Commons Math
> Issue Type: Improvement
> Reporter: Ryan Gaffney
> Priority: Minor
> Labels: patch, performance
> Fix For: 4.0
>
> Attachments: enum-distribution-perf-patch,
> enum-distribution-perf-patch.2
>
>
> There are lots of other low hanging fruit in the distribution package but
> unfortunately this is the only one I got to that day.
> In the EnumeratedDistribution case, the probability() method is currently
> O(N) where N denotes number of random variables, even though the random
> variables are fixed / known. This change makes probability() O(1). The
> unlikely worst case scenario now consumes slightly more than 2x the memory,
> but I do not think this would be an issue in the vast majority of cases.
> Original PR (incorrectly against master)
> [here|https://github.com/apache/commons-math/pull/34].
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