  In complex systems such as spin systems and protein systems, conventional
simulations in the canonical ensemble will get trapped in states of energy
local minima. We employ the generalized-ensemble algorithms in order to
overcome this multiple-minima problem. Three well-known generalized-ensemble
algorithms, namely, multicanonical algorithm, simulated tempering, and
replica-exchange method, are described. We then present three new
generalized-ensemble algorithms based on the combinations of the three methods.
Effectiveness of the new methods are tested with a Potts model and protein
systems.
