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From "Alex D Herbert (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (RNG-92) LargeMeanPoissonSampler cannot handle a mean less than 1
Date Mon, 15 Apr 2019 15:45:00 GMT

     [ https://issues.apache.org/jira/browse/RNG-92?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Alex D Herbert resolved RNG-92.
-------------------------------
       Resolution: Fixed
    Fix Version/s: 1.3

In master.

> LargeMeanPoissonSampler cannot handle a mean less than 1
> --------------------------------------------------------
>
>                 Key: RNG-92
>                 URL: https://issues.apache.org/jira/browse/RNG-92
>             Project: Commons RNG
>          Issue Type: Bug
>          Components: sampling
>    Affects Versions: 1.3
>            Reporter: Alex D Herbert
>            Assignee: Alex D Herbert
>            Priority: Major
>             Fix For: 1.3
>
>
> The LargeMeanPoissonSampler computes:
> {code:java}
> lambda = Math.floor(mean);
> logLambda = Math.log(lambda);
> {code}
> So if the mean is less than 1 the logLambda is NaN and other precomputed factors are
based on a lambda of zero. This results in infinite loop within the sampler method.
> Fix by removing support for a mean less than 1.



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