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From "Phil Steitz (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (MATH-654) ValueServer not deterministic for a fixed random number seed
Date Thu, 01 Sep 2011 00:15:10 GMT

     [ https://issues.apache.org/jira/browse/MATH-654?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Phil Steitz resolved MATH-654.
------------------------------

    Resolution: Fixed

Fixed in r1163875. ValueServer now exposes a reSeed method that when supplied a fixed seed
will generate a fixed sequence in any stochastic mode. The RandomDataImpl that it uses internally
is passed to the EmpiricalDistributionImpl it creates when used in DIGEST_MODE.  The changes
for this issue include an incompatible (vs. 2.x) change: the constructor for EmpiricalDistributionImpl
that previously took a RandomData now takes a RandomDataImpl.  The plan for 3.0 is to merge
these.

> ValueServer not deterministic for a fixed random number seed
> ------------------------------------------------------------
>
>                 Key: MATH-654
>                 URL: https://issues.apache.org/jira/browse/MATH-654
>             Project: Commons Math
>          Issue Type: Bug
>    Affects Versions: 1.1, 1.2, 2.0, 2.1, 2.2
>            Reporter: David James
>            Assignee: Phil Steitz
>             Fix For: 3.0
>
>
> I have built an agent-based model using the Apache Commons Math library, which has come
in handy.
> The ValueServer seemed particularly helpful, as explained at:
> http://commons.apache.org/math/userguide/random.html
> My simulation needs repeatable randomness, so I used this form of the ValueServer constructor:
>     ValueServer(RandomData randomData) 
>     Construct a ValueServer instance using a RandomData as its source of random data.
>     // http://commons.apache.org/math/api-2.2/org/apache/commons/math/random/ValueServer.html
> However, in my simulation, I found that the ValueServer did not act deterministically
if I supplied the same random number seed.
> I have not inspected the source code, but I suspect that the ValueServer is not using
the `randomData` generator correctly. If it was, then it should be deterministic.

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