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From Gilles Sadowski <gil...@harfang.homelinux.org>
Subject Re: svn commit: r995035 - /commons/proper/math/trunk/src/main/java/org/apache/commons/math/optimization/univariate/BrentOptimizer.java
Date Wed, 08 Sep 2010 15:37:52 GMT
> > URL: http://svn.apache.org/viewvc?rev=995035&view=rev
> > Log:
> > Removed strict equality comparison.
> 
> In some rare cases, strict equality comparison is desired (I don't know
> if it is the case here). In these cases, findbugs can be configured to
> ignore these cases, see the findbugs-exclude-filter.xml file for an example.

I don't know whether it is one of those rare cases. The algorithm
description in ALGOL uses the "=" sign while the FORTRAN implementation (in
the appendix) works around the problem by inversing the checks:
170 IF ((FU.GT.FW).AND.(W.NE.X)) GO TO 180
    V = W
    FV = FW
    W = U
    FW = FU
    GO TO 10
180 etc.

> > Modified: commons/proper/math/trunk/src/main/java/org/apache/commons/math/optimization/univariate/BrentOptimizer.java
> > URL: http://svn.apache.org/viewvc/commons/proper/math/trunk/src/main/java/org/apache/commons/math/optimization/univariate/BrentOptimizer.java?rev=995035&r1=995034&r2=995035&view=diff
> > ==============================================================================
> > --- commons/proper/math/trunk/src/main/java/org/apache/commons/math/optimization/univariate/BrentOptimizer.java
(original)
> > +++ commons/proper/math/trunk/src/main/java/org/apache/commons/math/optimization/univariate/BrentOptimizer.java
Wed Sep  8 12:51:38 2010
> > @@ -17,6 +17,7 @@
> >  package org.apache.commons.math.optimization.univariate;
> >  
> >  import org.apache.commons.math.FunctionEvaluationException;
> > +import org.apache.commons.math.util.MathUtils;
> >  import org.apache.commons.math.util.FastMath;
> >  import org.apache.commons.math.exception.NumberIsTooSmallException;
> >  import org.apache.commons.math.exception.NotStrictlyPositiveException;
> > @@ -219,12 +220,15 @@ public class BrentOptimizer extends Abst
> >                      } else {
> >                          b = u;
> >                      }
> > -                    if (fu <= fw || w == x) {
> > +                    if (fu <= fw ||
> > +                        MathUtils.equals(w, x)) {
> >                          v = w;
> >                          fv = fw;
> >                          w = u;
> >                          fw = fu;
> > -                    } else if (fu <= fv || v == x || v == w) {
> > +                    } else if (fu <= fv ||
> > +                               MathUtils.equals(v, x) ||
> > +                               MathUtils.equals(v, w)) {
> >                          v = u;
> >                          fv = fu;
> >                      }

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