Partially Observable Multiagent Reinforcement Learning with Information Sharing
Xiangyu Liu, Kaiqing Zhang · SIAM Journal on Control and Optimization · 2026
Abstract. We study provable multiagent reinforcement learning (RL) in the general framework of partially observable stochastic games (POSGs). To circumvent the known hardness results and the use of computationally intractable oracles, we advocate leveraging the potential information sharing among agents, a common practice in empirical multiagent RL, and a standard model for multiagent control systems with communication. We first establish several computational complexity results to justify the necessity of information sharing, as well as the observability assumption that has enabled quasi-polynomial time and sample single-agent RL with partial observations, for tractably solving POSGs. Inspired by the inefficiency of planning in the ground-truth model, we then propose to further approximate the shared common information to construct an approximate model of the POSG, in which an approximate equilibrium (of the original POSG) can be found in quasi-polynomial-time, under the aforementioned assumptions. Furthermore, we develop a partially observable multiagent RL algorithm whose time and sample complexities are both quasi-polynomial. Finally, beyond equilibrium learning, we extend our algorithmic framework to finding the team-optimal solution in cooperative POSGs, i.e., decentralized partially observable Markov decision processes, a more challenging goal. We establish concrete computational and sample complexities under several structural assumptions of the model. We hope our study could open up the possibilities of leveraging and even designing different information structures, a well-studied notion in control theory, for developing both sample- and computation-efficient partially observable multiagent RL.