  By combining two generalized-ensemble algorithms, Replica-Exchange
Wang-Landau (REWL) method and Multicanonical Replica-Exchange Method (MUCAREM),
we propose an effective simulation protocol to determine the density of states
with high accuracy. The new protocol is referred to as REWL-MUCAREM, and REWL
is first performed and then MUCAREM is performed next. In order to verify the
effectiveness of our protocol, we performed simulations of a square-lattice
Ising model by the three methods, namely, REWL, MUCAREM, and REWL-MUCAREM. The
results showed that the density of states obtained by the REWL-MUCAREM is more
accurate than that is estimated by the two methods separately.
