To apply potential contrasting, we first resample the conformations {x i : i = 1, ..., N } with replacement using the weights {w i : i = 1, ..., N } as the probability of selecting each conformation. The resampling procedure generates a new set of conformations {x p i : i = 1, ..., N }, which can be viewed as equilibrium samples from the reweighted ensemble Z ME 0 with equal weights. Our objective is to identify the force field parameters θ such that the canonical ensemble of the system p(x; θ) matches the distribution of the conformations