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Posted to issues@commons.apache.org by "Ryan Gaffney (JIRA)" <ji...@apache.org> on 2016/05/30 17:43:12 UTC

[jira] [Updated] (MATH-1370) Increase efficiency of EnumeratedDistribution#probability

     [ https://issues.apache.org/jira/browse/MATH-1370?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ryan Gaffney updated MATH-1370:
-------------------------------
    Attachment: enum-distribution-perf-patch

> 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
>         Attachments: enum-distribution-perf-patch
>
>
> 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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