D\'ej\`aVu: A Minimalistic Mechanism for Distributed Plurality Consensus

A team of researchers from institutions including Université Côte d'Azur and Sapienza University of Rome has introduced DéjàVu, a radically simple mechanism for distributed plurality consensus. The protocol addresses a fundamental problem in multi-agent systems: how can a population of extremely simple agents, each holding one of k initial opinions, efficiently agree on the most frequent one? Traditional approaches like h-majority require agents to sample a predetermined number (h) of neighbors, count frequencies, and choose the majority—processes that demand memory and parameter selection.

DéjàVu eliminates these complexities through an elegant rule: an agent repeatedly queries random neighbors until it encounters the same opinion twice, then immediately updates its own opinion to that duplicate value. This "detect repetition" primitive requires no counters, frequency estimation, or parameter choices like sample size h. The researchers' rigorous analysis, detailed in their arXiv preprint, demonstrates that DéjàVu is competitive with established h-majority protocols and, in specific operational regimes, achieves substantially higher communication efficiency. This breakthrough provides a minimalistic yet powerful building block for swarm robotics, sensor networks, and large-scale distributed AI systems where computational and memory resources are severely constrained.