  We describe a generalized scheme for the probability-changing cluster (PCC)
algorithm, based on the study of the finite-size scaling property of the
correlation ratio, the ratio of the correlation functions with different
distances. We apply this generalized PCC algorithm to the two-dimensional
6-state clock model. We also discuss the combination of the cluster algorithm
and the extended ensemble method. We derive a rigorous broad histogram relation
for the bond number. A Monte Carlo dynamics based on the number of potential
moves for the bond number is proposed, and applied to the three-dimensional
Ising and 3-state Potts models.
