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From "Gilles (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MATH-621) BOBYQA is missing in optimization
Date Sun, 21 Aug 2011 10:33:27 GMT

    [ https://issues.apache.org/jira/browse/MATH-621?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13088339#comment-13088339
] 

Gilles commented on MATH-621:
-----------------------------

Looking at the unit tests I see that, in the "assertEquals", tolerance for the function values
are not very stringent (e.g. 1e-8 instead of, say, 1e-15); so this means that your initial
translation was already not expected to reproduce exactly the "reference" results (Fortran
or C++ (?)). Am I correct?

So, in the "Ackley" case, the tolerance is set to 1e-8, and the alternative computation produces
"1.07319e-8" instead of "0.0". Thus the absolute change in tolerance is smaller than 1e-10,
which might be put on the account of error propagation (?).

However, in "DiffPow", the number of evaluations with the your original code is 6016, while
the alternative computation makes it fail even as 12000 are allowed. This looks like a much
more drastic change in behaviour!
Pardon my possible ignorance, but it makes we wonder whether the test is not too fragile or
whether there is a bug in the implementation... In other words it would have been a "lucky
accident" that the original computation succeeds.


> BOBYQA is missing in optimization
> ---------------------------------
>
>                 Key: MATH-621
>                 URL: https://issues.apache.org/jira/browse/MATH-621
>             Project: Commons Math
>          Issue Type: New Feature
>    Affects Versions: 3.0
>            Reporter: Dr. Dietmar Wolz
>             Fix For: 3.0
>
>         Attachments: BOBYQA.math.patch, BOBYQA.v02.math.patch, BOBYQAOptimizer.java.patch,
BOBYQAOptimizer0.4.zip, bobyqa.zip, bobyqa_convert.pl, bobyqaoptimizer0.4.zip, bobyqav0.3.zip
>
>   Original Estimate: 8h
>  Remaining Estimate: 8h
>
> During experiments with space flight trajectory optimizations I recently
> observed, that the direct optimization algorithm BOBYQA
> http://plato.asu.edu/ftp/other_software/bobyqa.zip
> from Mike Powell is significantly better than the simple Powell algorithm
> already in commons.math. It uses significantly lower function calls and is
> more reliable for high dimensional problems. You can replace CMA-ES in many
> more application cases by BOBYQA than by the simple Powell optimizer.
> I would like to contribute a Java port of the algorithm.
> I maintained the structure of the original FORTRAN code, so the
> code is fast but not very nice.
> License status: Michael Powell has sent the agreement via snail mail
> - it hasn't arrived yet.
> Progress: The attached patch relative to the trunk contains both the
> optimizer and the related unit tests - which are all green now.  
> Performance:
> Performance difference (number of function evaluations)
> PowellOptimizer / BOBYQA for different test functions (taken from
> the unit test of BOBYQA, dimension=13 for most of the
> tests. 
> Rosen = 9350 / 1283
> MinusElli = 118 / 59
> Elli = 223 / 58
> ElliRotated = 8626 / 1379
> Cigar = 353 / 60
> TwoAxes = 223 / 66
> CigTab = 362 / 60
> Sphere = 223 / 58
> Tablet = 223 / 58
> DiffPow = 421 / 928
> SsDiffPow = 614 / 219
> Ackley = 757 / 97
> Rastrigin = 340 / 64
> The number for DiffPow should be dicussed with Michael Powell,
> I will send him the details. 
> Open Problems:
> Some checkstyle violations because of the original Fortran source:
> - Original method comments were copied - doesn't follow javadoc standard
> - Multiple variable declarations in one line as in the original source
> - Problems related to "goto" conversions:
>   "gotos" not convertible in loops were transated into a finite automata (switch statement)
> 	"no default in switch"
> 	"fall through from previos case in switch"
> 	which usually are bad style make no sense here.

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