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https://issues.apache.org/jira/browse/MATH-1394?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17736747#comment-17736747
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Gilles Sadowski commented on MATH-1394:
---------------------------------------

{quote}
[...] transfer the functionality from the external repository to commons-math 
as well as the tests that come with it.
{quote}

That would be _forbidden_, because of the [incompatible 
license|https://www.apache.org/legal/resolved.html#category-x].
We must find either
* another implementation (with a compatible license), or
* a description of the algorithm to be implemented "from scratch".

Of course, a developer is allowed to _run_ the GPL code in order to compare its 
output with the one from the new implementation being developed.


> Implementation of DIRECT global optimizer
> -----------------------------------------
>
>                 Key: MATH-1394
>                 URL: https://issues.apache.org/jira/browse/MATH-1394
>             Project: Commons Math
>          Issue Type: New Feature
>    Affects Versions: 3.5, 3.6
>            Reporter: Kevin A. Burton
>            Priority: Major
>             Fix For: 4.X
>
>
> An open source implementation of the DIRECT global optimizer, described by 
> Jones, Perttunen and Stuckmann, implementing 
> math3.optim.nonlinear.scalar.MultivariateOptimizer, is available as 
> DIRECTOptimizer.java at 
> https://github.com/edwardkort/WWIDesigner/tree/optimizer/WWIDesigner/src/main/com/wwidesigner/math.
>   There are also three variants of the algorithm on that page: 
> DIRECT_L_Optimizer implements DIRECT-L by Gablonsky and Kelley, 
> DIRECT1Optimizer changes which sides are chosen for dividing, and 
> DIRECTCOptimizer adds alternative ways to select potentially-optimal 
> hyperrectangles.
> DIRECT is not as fast as BOBYQA, but is better at finding a global minimum in 
> a field of many local minima.
> JUnit tests for all of these, using standard optimizer test functions, are 
> available in 
> https://github.com/edwardkort/WWIDesigner/tree/optimizer/WWIDesigner/src/test/com/wwidesigner/math.



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