The Wolff single-cluster algorithm is the most efficient method known
for Monte Carlo simulation of many spin models. Due to the irregular s
ize, shape and position of the Wolff clusters, this method does not ea
sily lend itself to efficient parallel implementation, so that simulat
ions using this method have thus far been confined to workstations and
vector machines. Here we present two parallel implementations of this
algorithm, and show that one gives fairly good performance on a MIMD
parallel computer.