  Recent advances in Competitive Self-Play (CSP) have achieved, or even
surpassed, human level performance in complex game environments such as Dota 2
and StarCraft II using Distributed Multi-Agent Reinforcement Learning (MARL).
One core component of these methods relies on creating a pool of learning
agents -- consisting of the Main Agent, past versions of this agent, and
Exploiter Agents -- where Exploiter Agents learn counter-strategies to the Main
Agents. A key drawback of these approaches is the large computational cost and
physical time that is required to train the system, making them impractical to
deploy in highly iterative real-life settings such as video game productions.
In this paper, we propose the Minimax Exploiter, a game theoretic approach to
exploiting Main Agents that leverages knowledge of its opponents, leading to
significant increases in data efficiency. We validate our approach in a
diversity of settings, including simple turn based games, the arcade learning
environment, and For Honor, a modern video game. The Minimax Exploiter
consistently outperforms strong baselines, demonstrating improved stability and
data efficiency, leading to a robust CSP-MARL method that is both flexible and
easy to deploy.
