code: private double getConstraint(double x1, double x2)
     {
        double c1,c2,h;
        c1 = -x1*x1-x2*x2+1+0.1*Math.cos(16*Math.atan(x1/x2));
        c2 = (x1-0.5)*(x1-0.5)+(x2-0.5)*(x2-0.5)-0.5;
        if(c1>c2)
           h = (c1>0)?c1:0;
        else
           h = (c2>0)?c2:0;
        return h;
     }
docs: use the design parameters to compute the constraint equation to get the value