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https://issues.apache.org/jira/browse/MATH-1370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15306971#comment-15306971
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Gilles commented on MATH-1370:
------------------------------
Do you agree that the method {{probability}} defined as follows:
{noformat}
double probability(final T x) {
final Double p = massPoints.get(x);
return p == null ? 0 : p.doubleValue();
}
{noformat}
is a slight improvement over your version (only 1 lookup)?
> 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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