Java Double Number Divide divergenceKL(double... a)

Description

divergence KL

License

Open Source License

Declaration

public static double divergenceKL(double... a) 

Method Source Code

//package com.java2s;

public class Main {
    private static final double EPSILON = 1.0E-10;

    public static double divergenceKL(double... a) {
        double result = 0.0;
        double mean = boundBelow(mean(a), 0.0);
        for (int i = 0; i < a.length; i++) {
            result += divergenceKL(a[i], mean);
        }//w  ww  . ja  v a2 s .  c  om
        return result / a.length;
    }

    public static double divergenceKL(double pa, double pb) {
        pa = boundBelow(pa, 0.0);
        double pA = boundBelow(1.0 - pa, 0.0);
        double pB = 1.0 - pb;
        double result = pa * (Math.log(pa) - Math.log(pb)) + pA * (Math.log(pA) - Math.log(pB));

        if (Double.isNaN(result)) {
            System.out.println(pa + " " + pb);
            System.out.println(Math.log(pa) + " " + Math.log(pb));
            System.out.println(Math.log(pA) + " " + Math.log(pB));
        }
        return result;
    }

    public static double boundBelow(double a, double lower) {
        if (a <= lower + EPSILON)
            return lower + EPSILON;
        return a;
    }

    public static double mean(double[] a) {
        return mean(a, 0, a.length);
    }

    public static double mean(double[] a, int from, int to) {
        double mean = 0.0;
        for (int i = from; i < to; i++) {
            mean += a[i];
        }
        return mean / (to - from);
    }
}

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