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From "Rob Tompkins (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MATH-1338) Does "EmpiricalDistribution" use "RandomDataGenerator"?
Date Fri, 25 Mar 2016 14:26:25 GMT

    [ https://issues.apache.org/jira/browse/MATH-1338?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15211878#comment-15211878
] 

Rob Tompkins commented on MATH-1338:
------------------------------------

In line with MATH-1158, would you continue the pattern in both {{AbstractIntegerDistribution}}
and {{AbstractMultivariateRealDistribution}}? It seems reasonable to at least implement analogs
to the Sampler in those locations as well. 

> Does "EmpiricalDistribution" use "RandomDataGenerator"?
> -------------------------------------------------------
>
>                 Key: MATH-1338
>                 URL: https://issues.apache.org/jira/browse/MATH-1338
>             Project: Commons Math
>          Issue Type: Bug
>            Reporter: Gilles
>            Priority: Blocker
>              Labels: api, cleanup, exception
>             Fix For: 4.0
>
>
> The class {{EmpiricalDistribution}} (in package "o.a.c.m.random") holds an instance field
("randomData") of type {{RandomDataGenerator}}.
> The documentation of this field indicates that it is only used for sampling, and indeed
the field is only accessed in order to fetch the RNG object stored in it. 
> It is unclear why {{RandomDataGenerator}} was needed to hold a RNG since the same RNG
could have been (in the current design) readily available in the base class.
> Sampling is performed in method {{getNextValue()}} (which in turn calls {{sample()}}
in the parent class).
> {{getNextValue()}} performs a precondition check before calling {{sample()}} and raises
a CM specific {{MathIllegalStateException}}; but the inherited {{sample()}} method can be
still called directly on the instance, and in that case, if the (same) condition is not fulfilled,
a standard {{NullPointerException}} will be thrown instead.
> In line with MATH-1158, the sampling functionality should be accessed through the {{RealDistribution.Sampler}}
interface, and {{getNextValue()}} is to be removed as it duplicates the common API (i.e. the
{{sample()}} method).
> Since the RNG is then passed to the {{createSampler}} factory method, the "randomData"
field becomes obsolete.



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