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https://issues.apache.org/jira/browse/MATH-1293?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15010789#comment-15010789
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Aleksei Dievskii commented on MATH-1293:
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Gilles, thanks for your response. However, I don't quite understand what do you
mean. Should I create a package-local class which would contain only the
constants and the method to retrieve them (and extensive documentation, of
course), and then make factorialLog delegate to that method?
> Tabulating the logarithmic factorial
> ------------------------------------
>
> Key: MATH-1293
> URL: https://issues.apache.org/jira/browse/MATH-1293
> Project: Commons Math
> Issue Type: Improvement
> Affects Versions: 3.5
> Reporter: Aleksei Dievskii
> Priority: Minor
> Labels: feature, patch
> Attachments: factlog.patch
>
>
> Presently, CombinatoricsUtils#factorialLog is calculated via a tabulated
> value for the first 21 entries, and for the rest it employs linear-complexity
> direct summing. For the factorial-heavy computations this can be rather
> painful. I propose a patch which allocates additional 16KB of tabulated
> log-factorial values, allowing very fast (constant complexity) computation
> for arguments up to 17000, and delegating to the log-gamma for the rest.
> Benchmarks show a speed-up of up to 200x.
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