“…More recently, energy preserving Runge-Kutta methods of order two have been derived in [12], based on the concept of discrete line integral. This idea, further developed, has led to fourth order examples of conservative Runge-Kutta methods [13,14] and, finally, to Hamiltonian Boundary Value Methods (HBVMs) [3,2,4,5,6,7,8], a class of energy-preserving Runge-Kutta methods of any high order. Even though energy-conservation is an important feature for the discrete dynamical system induced by the methods, many Hamiltonian problems (and, in general, conservative problems) are characterized by the presence of multiple invariants.…”