  In Hybrid Monte Carlo(HMC) simulations for full QCD, the gauge fields evolve
smoothly as a function of Molecular Dynamics (MD) time. Thus we investigate
improved methods of estimating the trial solutions to the Dirac propagator as
superpositions of the solutions in the recent past. So far our best
extrapolation method reduces the number of Conjugate Gradient iterations per
unit MD time by about a factor of 4. Further improvements should be forthcoming
as we further exploit the information of past trajectories.
