@Override
    protected double doSolve() {
        double min = getMin();
        double max = getMax();
        // [x1, x2] is the bracketing interval in each iteration
        // x3 is the midpoint of [x1, x2]
        // x is the new root approximation and an endpoint of the new interval
        double x1 = min;
        double y1 = computeObjectiveValue(x1);
        double x2 = max;
        double y2 = computeObjectiveValue(x2);

        // check for zeros before verifying bracketing
        if (y1 == 0) {
            return min;
        }
        if (y2 == 0) {
            return max;
        }
        verifyBracketing(min, max);

        final double absoluteAccuracy = getAbsoluteAccuracy();
        final double functionValueAccuracy = getFunctionValueAccuracy();
        final double relativeAccuracy = getRelativeAccuracy();

        double oldx = Double.POSITIVE_INFINITY;
        while (true) {
            // calculate the new root approximation
            final double x3 = 0.5 * (x1 + x2);
            final double y3 = computeObjectiveValue(x3);
            if (FastMath.abs(y3) <= functionValueAccuracy) {
                return x3;
            }
            final double delta = 1 - (y1 * y2) / (y3 * y3);  // delta > 1 due to bracketing
            final double correction = (FastMath.signum(y2) * FastMath.signum(y3)) *
                                      (x3 - x1) / FastMath.sqrt(delta);
            final double x = x3 - correction;                // correction != 0
            final double y = computeObjectiveValue(x);

            // check for convergence
            final double tolerance = FastMath.max(relativeAccuracy * FastMath.abs(x), absoluteAccuracy);
            if (FastMath.abs(x - oldx) <= tolerance) {
                return x;
            }
            if (FastMath.abs(y) <= functionValueAccuracy) {
                return x;
            }

            // prepare the new interval for next iteration
            // Ridders' method guarantees x1 < x < x2
            if (correction > 0.0) {             // x1 < x < x3
                if (FastMath.signum(y1) + FastMath.signum(y) == 0.0) {
                    x2 = x;
                    y2 = y;
                } else {
                    x1 = x;
                    x2 = x3;
                    y1 = y;
                    y2 = y3;
                }
            } else {                            // x3 < x < x2
                if (FastMath.signum(y2) + FastMath.signum(y) == 0.0) {
                    x1 = x;
                    y1 = y;
                } else {
                    x1 = x3;
                    x2 = x;
                    y1 = y3;
                    y2 = y;
                }
            }
            oldx = x;
        }
    }