  We study efficiency of higher order integrator schemes for the hybrid Monte
Carlo (HMC) algorithm. Numerical tests are performed for Quantum Chromo
Dynamics (QCD) with two flavors of Wilson fermions. We compare 2nd, 4th and 6th
order integrators at various quark masses. The performance depends on both
volume and quark mass. On currently accessible large lattices ($V \sim 24^4$),
higher order integrators can be more efficient than the 2nd order one only in
heavy quark region, $m_q a > 0.3$. Thus we conclude that for most full QCD
simulations, except for heavy quark case, the usual 2nd order integrator is the
best choice.
