docs: protected static double change( EllipseRotated_F64 a , EllipseRotated_F64 b ) {
  		double total = 0;
  
  		total += Math.abs(a.center.x - b.center.x);
  		total += Math.abs(a.center.y - b.center.y);
  		total += Math.abs(a.a - b.a);
  		total += Math.abs(a.b - b.b);
  
  		// only care about the change of angle when it is not a circle
  		double weight = Math.min(4,2.0*(a.a/a.b-1.0));
  		total += weight*UtilAngle.distHalf(a.phi , b.phi);
  
  		return total;
  	}