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From "Dennis Hendriks (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MATH-764) New sample() API should accept RandomGenerator as parameter
Date Wed, 30 May 2012 14:08:23 GMT

    [ https://issues.apache.org/jira/browse/MATH-764?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13285680#comment-13285680
] 

Dennis Hendriks commented on MATH-764:
--------------------------------------

bq. I think that adding a RandomData instance as additional state to the Distribution classes
would really add a new "responsibility" to the Distribution classes that muddies the API.


Actually, they already have this. For instance, AbstractRealDistribution has this:

{code}
/** RandomData instance used to generate samples from the distribution. */
protected final RandomDataImpl randomData = new RandomDataImpl();
{code}

The only problem is that we can't control what randomData contains, as it is fixed in the
declaration of the field. Providing it via a constructor would solve this.

                
> New sample() API should accept RandomGenerator as parameter
> -----------------------------------------------------------
>
>                 Key: MATH-764
>                 URL: https://issues.apache.org/jira/browse/MATH-764
>             Project: Commons Math
>          Issue Type: Improvement
>    Affects Versions: 3.0
>            Reporter: Alex Bertram
>         Attachments: sampler-refactor.diff
>
>   Original Estimate: 48h
>  Remaining Estimate: 48h
>
> This may come to late as I know the 3.0 release is nearing completion, but I had some
concerns about the new sample() method on the math3 RealDistribution interface. 
> Specifically, there doesn't seem to be a way to supply a random generator to the sampler.
Perhaps it would be better to have a factory method on the RealDistribution interface that
accepted a RandomGenerator and returns an instance of some new interface, Sampler, which contains
the sample() methods. 
> That is:
> interface RealDistribution {
>     Sampler createSampler(RandomGenerator generator);
>     Sample createSampler(); // uses default RandomGenerator
> }
> interface Sampler {
>     double sample();
>     double[] sample(int sampleSize);
> }

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