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https://issues.apache.org/jira/browse/MATH-1370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15307011#comment-15307011
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Ryan Gaffney commented on MATH-1370:
------------------------------------
[~erans]
{quote}Is the additional unit test (in a new file) really necessary?
Does it test more than EnumeratedIntegerDistributionTest?{quote}
It is also testing the {{getPmf()}} function which is specific to
EnumeratedDistribution. (I did not want to break the behavior for nulls)
>From the JavaDoc: {{Note that if duplicate and / or null values were provided
>to the constructor when creating this EnumeratedDistribution, the returned
>list will contain these values.}}
{quote}Do you agree that the method probability defined as follows: [...]{quote}
Along the same lines as my previous response, the integer distribution classes
allow for null values. With the change you would always return {{0}} for
{{null}} even though that might be a valid random variable. It would therefore
break the added test on L47.
_Note that I was just keeping parity with the original code; I am not arguing
over whether or not we should allow null random variables_ :)
> 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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