public class MultiGradient {

    public static void main (String[] argv)
    {
        gradientDescent (0,10, 0,10);
    }

    static void gradientDescent (double a1, double b1, double a2, double b2)
    {
        int n = 1;
        double x1 = a1, x2 = a2;
        double alpha = 1;
        double epsilon = 0.001;
        double f1 = 2*epsilon, f2 = 2*epsilon;

        while ( (Math.abs(f1) > epsilon) || (Math.abs(f2) > epsilon) ) {
            f1 = computeDeriv1 (x1,x2);
            f2 = computeDeriv2 (x1,x2);
            x1 = x1 - alpha * f1;
            x2 = x2 - alpha * f2;
            n ++;
        }

        System.out.println ("Gradient descent: after n=" + n + " iterations: x1=" + x1 + " x2=" + x2);
    }

    static double computef (double x1, double x2)
    {
        return (x1-4.71)*(x1-4.71) + (x2-3.2)*(x2-3.2) + 2*(x1-4.71)*(x1-4.71)*(x2-3.2)*(x2-3.2);
    }

    static double computeDeriv1 (double x1, double x2)
    {
        //  INSERT YOUR CODE HERE.
    }

    static double computeDeriv2 (double x1, double x2)
    {
        //  INSERT YOUR CODE HERE.
    }

}