Early Decision and Stopping in Synchronous Consensus: A Predicate-Based Guided Tour

Consensus is the most basic agreement problem encountered in fault-tolerant distributed computing: each process proposes a value and non-faulty processes must agree on the same value, which has to be one of the proposed values. While this problem is impossible to solve in asynchronous systems prone to process crash failures, it can be solved in synchronous (round-based) systems where all but one process might crash in any execution. It is well-known that \((t+1)\) rounds are necessary and sufficient in the worst case execution scenario for the processes to decide and stop executing, where \(t < n\) is a system parameter denoting the maximum number of allowed process crashes and n denotes the number of processes in the system.