AN O(1) RMRs LEADER ELECTION ALGORITHM

The leader election problem is a fundamental coordination problem. We present leader election algorithms for multiprocessor systems where processes communicate by reading and writing shared memory asynchronously and do not fail. In particular, we consider the cache-coherent (CC) and distributed shared memory (DSM) models of such systems. We present leader election algorithms that perform a constant number of remote memory references (RMRs) in the worst case. Our algorithms use splitter-like objects [J. Anderson and M. Moir, Sci. Comput. Programming, 25 (1995), pp. 1-39; H. Attiya and A. Fouren, Theory Comput. Syst., 31 (2001), pp. 642-664] in a novel way, by organizing active processes into teams that share work. As there is an Ω(log n) lower bound on the RMR complexity of mutual exclusion for n processes using reads and writes only, our result separates the mutual exclusion and leader election problems in terms of RMR complexity in both the CC and DSM models.