# Fully Decentralized Multi-Agent Reinforcement Learning with Networked Agents

## TL;DR

This paper introduces fully decentralized multi-agent reinforcement learning algorithms for networked agents with provable convergence, enabling large-scale, online, and distributed decision-making without centralized control.

## Contribution

It presents the first fully decentralized MARL algorithms with convergence guarantees, applicable to large-scale problems with function approximation.

## Key findings

- Algorithms are fully incremental and online.
- Convergence is proven for linear function approximation.
- Extensive simulations validate effectiveness.

## Abstract

We consider the problem of \emph{fully decentralized} multi-agent reinforcement learning (MARL), where the agents are located at the nodes of a time-varying communication network. Specifically, we assume that the reward functions of the agents might correspond to different tasks, and are only known to the corresponding agent. Moreover, each agent makes individual decisions based on both the information observed locally and the messages received from its neighbors over the network. Within this setting, the collective goal of the agents is to maximize the globally averaged return over the network through exchanging information with their neighbors. To this end, we propose two decentralized actor-critic algorithms with function approximation, which are applicable to large-scale MARL problems where both the number of states and the number of agents are massively large. Under the decentralized structure, the actor step is performed individually by each agent with no need to infer the policies of others. For the critic step, we propose a consensus update via communication over the network. Our algorithms are fully incremental and can be implemented in an online fashion. Convergence analyses of the algorithms are provided when the value functions are approximated within the class of linear functions. Extensive simulation results with both linear and nonlinear function approximations are presented to validate the proposed algorithms. Our work appears to be the first study of fully decentralized MARL algorithms for networked agents with function approximation, with provable convergence guarantees.