Commitment-driven distributed joint policy search

Abstract

Decentralized MDPs provide powerful models of interactions in multiagent environments, but are often very difficult or even computationally infeasible to solve optimally. Here we develop a hierarchical approach to solving a restricted set of decentralized MDPs. By forming commitments with other agents and modeling these concisely in their local MDPs, agents effectively, efficiently, and distributively formulate co-ordinated local policies. We introduce a novel construction that captures commitments as constraints on local policies and show how Linear Programming can be used to achieve local optimality subject to these constraints. In contrast to other commitment enforcement approaches, we show ours to be more robust in capturing the intended commitment semantics while maximizing local utility. We also describe a commitment-space heuristic search algorithm that can be used to approximate optimal joint policies. A preliminary empirical evaluation suggests that our approach yields faster approximate solutions than the conventional encoding of the problem as a multiagent MDP would allow and, when wrapped in an exhaustive commitment-space search, will find the optimal global solution.