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Date: Thu, 18 Mar 2010 21:08:27 +0000 (UTC)
From: "Michael Sammeth (JIRA)" <jira@apache.org>
To: issues@commons.apache.org
Subject: [jira] Created: (MATH-354) compiler dependency in
 RandomDataImpl.getPoisson(double mean)
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compiler dependency in RandomDataImpl.getPoisson(double mean)
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                 Key: MATH-354
                 URL: https://issues.apache.org/jira/browse/MATH-354
             Project: Commons Math
          Issue Type: Bug
    Affects Versions: 2.0
         Environment: jre1.5/jre1.6
            Reporter: Michael Sammeth


Hi,

in RandomDataImpl.getPoisson(double mean) I got the following problem in the case mean>= 6.0:

in the branch if (u <= c1):

if (x < -mu)
    w = Double.POSITIVE_INFINITY;

implicits that (int) (mu+ x) < 0

I found that for some compiler/run-time environments the subsequent update of the "accept" value then fails, as by the right hand side of the comparison leads to an Exception in MathUtils.factorialLog((int) (mu + x)). Some compiler/jre combinations, however, skip evaluating the right side as by isInfinity(w).

To ensure stability, I currently worked around by an explicit if(Double.isInfinity(w)) branch, however, I would like to ask whether there is a more elegant way to ensure general functionality of that method.

Thank you, micha. 

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