A NOTE ON THE DETERMINATION OF THE IMMEDIATE PREDECESSORS IN A DISTRIBUTED COMPUTATION
Emmanuelle Anceaume, Jean-Michel Hélary, Michel Raynal · International Journal of Foundations of Computer Science · 2002
A distributed computation can be modeled as a partially ordered set (poset) of relevant events (the relevant events are the subset of the primitive events that are meaningful for an observer). This short note presents a general protocol that, when superimposed on a distributed computation, provides each relevant event with a timestamp that identifies exactly its immediate predecessors in the poset. This determination is done on the fly and without using additional control messages. So, the proposed protocol provides an on the fly computation of the Hasse diagram (transitive reduction) of the event graph produced by a distributed computation. The protocol is particularly simple and efficient. It is based on a general condition that allows application messages to piggyback control information whose size can be smaller than n (the number of processes). Interestingly, when one is not interested in tracking the immediate predecessors, the proposed protocol can be simplified to get an efficient vector clock protocol that does not require particular channel assumptions.