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https://issues.apache.org/jira/browse/MATH-724?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dennis Hendriks updated MATH-724:
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Attachment: NextIntUniformTest.java
NextIntUniformTest.java: see issue description
> RandomDataImpl.nextInt does not distribute uniformly for negative lower bound
> -----------------------------------------------------------------------------
>
> Key: MATH-724
> URL: https://issues.apache.org/jira/browse/MATH-724
> Project: Commons Math
> Issue Type: Bug
> Affects Versions: Nightly Builds
> Reporter: Dennis Hendriks
> Attachments: NextIntUniformTest.java
>
>
> 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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