method to overload to compute grad_f, the first derivative of the cost function with respect to x
method to overload to compute J_f, the jacobian of the cost function with respect to x
method to overload to compute grad_f, the first derivative of the cost function with respect to x and also the cost function
method to overload to compute J_f, the jacobian of the cost function with respect to x and also the cost function
method to overload to compute grad_f, the first derivative of the cost function with respect to x