Verification of the Randomized Consensus Algorithm of Aspnes and Herlihy: a Case Study*

Abstract

The Probabilistic I/O Automaton model of [20] is used as the basis for a formal presentation and proof of the randomized consensus algorithm of Aspnes and Herlihy. The algorithm guarantees termination within expected polynomial time. The Aspnes-Herlihy algorithm is a rather complex algorithm. Processes move through a succesion of asynchronous rounds, attempting to agree at each round. At each round, the agreement attempt involves a distributed random walk.