Leaders and Collaborators: Addressing Sparse Reward Challenges in Multi-Agent Reinforcement Learning

Cooperative multi-agent reinforcement learning (MARL) has emerged as an effective tool for addressing complex control tasks. However, sparse team rewards present significant challenges for MARL, leading to low exploration efficiency, slow learning speed, and homogenized behaviors among agents. To address these issues, we propose a novel Leader-Collaborator (LC) MARL framework inspired by human social collaboration. The LC framework introduces parallel online knowledge distillation for policy networks (KDPN). KDPN extracts knowledge from two policy networks with different training objectives: one aims to maximize individual rewards, while the other aims to maximize team rewards. The extracted knowledge is utilized to construct team leaders and collaborators. By effectively balancing individual and team rewards, our approach enhances exploration efficiency and promotes behavioral diversity among agents. This addresses the issue of low learning efficiency caused by the lack of objectives early in the agent's learning process and facilitates the development of more effective and differentiated team interaction policies. Additionally, we present the Self-Repairing Strategy (SRS) and Self-Augmenting Strategy (SAS) to facilitate team policies learning while preserving the initial team goal. We evaluate the effectiveness of the LC framework by conducting extensive experiments on the Multi-Agent Particle Environment (MPE), the Google Research Football (GRF), and StarCraft Multi-Agent Challenge (SMAC) with varying levels of difficulty. Our experimental results demonstrate that LC significantly improves the efficiency of the agent's exploration, achieves state-of-the-art performance, and accelerates the learning of the optimal policy. Specifically, in the SMAC scenarios, our method increases the winning rate by 21.9%, increases the average cumulative reward by 12%, and reduces the training time by 57% to achieve optimal performance.