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From "Ryan Gaffney (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (MATH-1370) Increase efficiency of EnumeratedDistribution#probability
Date Tue, 31 May 2016 01:41:12 GMT

    [ https://issues.apache.org/jira/browse/MATH-1370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15307011#comment-15307011
] 

Ryan Gaffney edited comment on MATH-1370 at 5/31/16 1:41 AM:
-------------------------------------------------------------

[~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_ :)-

Disregard, see [comment below|https://issues.apache.org/jira/browse/MATH-1370?focusedCommentId=15307069&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15307069]


was (Author: rg_):
[~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, 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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