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List:       jakarta-commons-dev
Subject:    [jira] [Commented] (MATH-1153) Sampling from a 'BetaDistribution' is slow
From:       "Thomas Neidhart (JIRA)" <jira () apache ! org>
Date:       2015-04-30 21:09:06
Message-ID: JIRA.12744980.1412092174000.39790.1430428146238 () Atlassian ! JIRA
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    [ https://issues.apache.org/jira/browse/MATH-1153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14522272#comment-14522272 \
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Thomas Neidhart commented on MATH-1153:
---------------------------------------

I did not write a jmh benchmark yet, but it looks like that for alpha/beta values < 1 \
the variant with sampling from a gamma distribution is faster, while for values > 1 \
the cheng sampling method is slightly faster.

The difference is just small, and is probably negligible once the code has been \
compiled natively.

> Sampling from a 'BetaDistribution' is slow
> ------------------------------------------
> 
> Key: MATH-1153
> URL: https://issues.apache.org/jira/browse/MATH-1153
> Project: Commons Math
> Issue Type: Improvement
> Reporter: Sergei Lebedev
> Priority: Minor
> Fix For: 4.0
> 
> Attachments: ChengBetaSampler.java, ChengBetaSampler.java, \
> ChengBetaSamplerTest.java 
> 
> Currently the `BetaDistribution#sample` uses inverse CDF method, which is quite \
> slow for sampling-intensive computations. I've implemented a method from the R. C. \
> H. Cheng paper and it seems to work much better. Here's a simple microbenchmark: \
> {code} o.j.b.s.SamplingBenchmark.algorithmBCorBB       1e-3    1000  thrpt        5 \
> 2592200.015    14391.520  ops/s o.j.b.s.SamplingBenchmark.algorithmBCorBB       \
> 1000    1000  thrpt        5  3210800.292    33330.791  ops/s \
> o.j.b.s.SamplingBenchmark.commonsVersion        1e-3    1000  thrpt        5    \
> 31034.225      438.273  ops/s o.j.b.s.SamplingBenchmark.commonsVersion        1000  \
> 1000  thrpt        5    21834.010      433.324  ops/s {code}
> Should I submit a patch?
> R. C. H. Cheng (1978). Generating beta variates with nonintegral shape parameters. \
> Communications of the ACM, 21, 317–322.



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