[jira] [Commented] (MATH-621) BOBYQA is missing in optimization

["Gilles (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MATH-621?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13132127#comment-13132127 ] 

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

Hi Dietmar.

Could you please have a look at revision 1185917?
I'm worried that this seems like a sensitivity to the limited precision of the floating point representation of numbers.
I recall that you mentioned you had detected this kind of behaviour.
I think that, if this is intended behaviour, its rationale should be documented; otherwise, one can only wonder why a logically equivalent statement might break the algorithm.
However, I'd prefer to think that the unit tests are too stringent, i.e. that the mathematical algorithm is actually robust and that the the tolerance in the failing unit tests should be adapted to take into account the limited precision. Or probably even better: that it would be possible to detect that the numerical procedure is in trouble (due to a too low tolerance) and throw an appropriate exception instead of fail after exhausting the evaluations counter (there was a similar problem in issue MATH-631).

Equally worrisome is the fact that not all the branches are covered by the "baseline" unit tests, so that my inserting bugs in statements there will go unnoticed! :(
Do you have ideas on how to increase the coverage (in a controlled way)?
                
> 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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