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From "Phil Steitz (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (MATH-724) 1
Date Tue, 20 Dec 2011 21:09:30 GMT

     [ https://issues.apache.org/jira/browse/MATH-724?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Phil Steitz updated MATH-724:
-----------------------------

    Affects Version/s:     (was: Nightly Builds)
                       1.0
                       1.1
                       1.2
                       2.0
                       2.1
                       2.2
        Fix Version/s: 3.0
              Summary: 1  (was: RandomDataImpl.nextInt does not distribute uniformly for negative
lower bound)
    
> 1
> -
>
>                 Key: MATH-724
>                 URL: https://issues.apache.org/jira/browse/MATH-724
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 1.0, 1.1, 1.2, 2.0, 2.1, 2.2
>            Reporter: Dennis Hendriks
>             Fix For: 3.0
>
>         Attachments: NextIntTest3.java, NextIntUniformTest.java, NextUniformTest3.java,
math-724-v2.patch, math-724-v3.patch, math-724.patch
>
>
> When using the RandomDataImpl.nextInt function to get a uniform sample in a [lower, upper]
interval, when the lower value is less than zero, the output is not uniformly distributed,
as the lowest value is practically never returned.
> See the attached NextIntUniformTest.java file. It uses a [-3, 5] interval. For several
values between 0 and 1, testNextIntUniform1 prints the return value of RandomDataImpl.nextInt
(as double and as int). We see that -2 through 5 are returned several times. The -3 value
however, is only returned for 0.0, and is thus under-respresented in the integer samples.
The output of test method testNextIntUniform2 also clearly shows that value -3 is never sampled.

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