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https://issues.apache.org/jira/browse/MATH-1021?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Thomas Neidhart resolved MATH-1021.
-----------------------------------
Resolution: Fixed
Fix Version/s: 3.3
> HypergeometricDistribution.sample suffers from integer overflow
> ---------------------------------------------------------------
>
> Key: MATH-1021
> URL: https://issues.apache.org/jira/browse/MATH-1021
> Project: Commons Math
> Issue Type: Bug
> Reporter: Brian Bloniarz
> Fix For: 3.3
>
>
> Hi, I have an application which broke when ported from commons math 2.2 to
> 3.2. It looks like the HypergeometricDistribution.sample() method doesn't
> work as well as it used to with large integer values -- the example code
> below should return a sample between 0 and 50, but usually returns -50.
> {code}
> import org.apache.commons.math3.distribution.HypergeometricDistribution;
> public class Foo {
> public static void main(String[] args) {
> HypergeometricDistribution a = new HypergeometricDistribution(
> 43130568, 42976365, 50);
> System.out.printf("%d %d%n", a.getSupportLowerBound(),
> a.getSupportUpperBound()); // Prints "0 50"
> System.out.printf("%d%n",a.sample());
> // Prints "-50"
> }
> }
> {code}
> In the debugger, I traced it as far as an integer overflow in
> HypergeometricDistribution.getNumericalMean() -- instead of doing
> {code}
> return (double) (getSampleSize() * getNumberOfSuccesses()) / (double)
> getPopulationSize();
> {code}
> it could do:
> {code}
> return getSampleSize() * ((double) getNumberOfSuccesses() / (double)
> getPopulationSize());
> {code}
> This seemed to fix it, based on a quick test.
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