Event-Triggered Distributed Inference

We study a setting where each agent in a network receives certain private signals generated by an unknown static state that belongs to a finite set of hypotheses. The agents are tasked with collectively identifying the true state. To solve this problem in a communication-efficient manner, we propose an event-triggered distributed learning algorithm that is based on the principle of diffusing low beliefs on each false hypothesis. Building on this principle, we design a trigger condition under which an agent broadcasts only those components of its belief vector that have adequate innovation, to only those neighbors that require such information. We establish that under standard assumptions, each agent learns the true state exponentially fast almost surely. We also identify sparse communication regimes where the inter-communication intervals grow unbounded, and yet, the asymptotic learning rate of our algorithm remains the same as the best known rate for this problem. We then establish, both in theory and via simulations, that our event-triggering strategy has the potential to significantly reduce information flow from uninformative agents to informative agents. Finally, we argue that, as far as only asymptotic learning is concerned, one can allow for arbitrarily sparse communication patterns.