private static double euclidean()

in commons-numbers-core/src/main/java/org/apache/commons/numbers/core/Norm.java [339:398]
44 lines of code
4 McCabe index (conditional complexity)

    private static double euclidean(final double x,
                                    final double y,
                                    final double z) {
        final double xabs = Math.abs(x);
        final double yabs = Math.abs(y);
        final double zabs = Math.abs(z);

        final double max = Math.max(Math.max(xabs, yabs), zabs);

        // if the max is not finite, then one of the inputs must not have
        // been finite
        if (!Double.isFinite(max)) {
            // let the standard multiply operation determine whether to
            // return NaN or infinite
            return xabs * yabs * zabs;
        }

        // compute the scale and rescale values
        final double scale;
        final double rescale;
        if (max > LARGE_THRESH) {
            scale = SCALE_DOWN;
            rescale = SCALE_UP;
        } else if (max < SAFE_SCALE_UP_THRESH) {
            scale = SCALE_UP;
            rescale = SCALE_DOWN;
        } else {
            scale = 1d;
            rescale = 1d;
        }

        double sum = 0d;
        double comp = 0d;

        // add scaled x
        final double sx = xabs * scale;
        final double px = sx * sx;
        comp += ExtendedPrecision.squareLowUnscaled(sx, px);
        final double sumPx = sum + px;
        comp += ExtendedPrecision.twoSumLow(sum, px, sumPx);
        sum = sumPx;

        // add scaled y
        final double sy = yabs * scale;
        final double py = sy * sy;
        comp += ExtendedPrecision.squareLowUnscaled(sy, py);
        final double sumPy = sum + py;
        comp += ExtendedPrecision.twoSumLow(sum, py, sumPy);
        sum = sumPy;

        // add scaled z
        final double sz = zabs * scale;
        final double pz = sz * sz;
        comp += ExtendedPrecision.squareLowUnscaled(sz, pz);
        final double sumPz = sum + pz;
        comp += ExtendedPrecision.twoSumLow(sum, pz, sumPz);
        sum = sumPz;

        return Math.sqrt(sum + comp) * rescale;
    }