Multiparty Dynamics and Failure Modes for Machine Learning and Artificial Intelligence

An important challenge for safety in machine learning and artificial intelligence systems is a~set of related failures involving specification gaming, reward hacking, fragility to distributional shifts, and Goodhart's or Campbell's law. This paper presents additional failure modes for interactions within multi-agent systems that are closely related. These multi-agent failure modes are more complex, more problematic, and less well understood than the single-agent case, and are also already occurring, largely unnoticed. After motivating the discussion with examples from poker-playing artificial intelligence (AI), the paper explains why these failure modes are in some senses unavoidable. Following this, the paper categorizes failure modes, provides definitions, and cites examples for each of the modes: accidental steering, coordination failures, adversarial misalignment, input spoofing and filtering, and goal co-option or direct hacking. The paper then discusses how extant literature on multi-agent AI fails to address these failure modes, and identifies work which may be useful for the mitigation of these failure modes.Comment: 12 Pages, This version re-submitted to Big Data and Cognitive Computing, Special Issue "Artificial Superintelligence: Coordination & Strategy

Opponent modeling and exploitation in poker using evolved recurrent neural networks

As a classic example of imperfect information games, poker, in particular, Heads-Up No-Limit Texas Holdem (HUNL), has been studied extensively in recent years. A number of computer poker agents have been built with increasingly higher quality. While agents based on approximated Nash equilibrium have been successful, they lack the ability to exploit their opponents effectively. In addition, the performance of equilibrium strategies cannot be guaranteed in games with more than two players and multiple Nash equilibria. This dissertation focuses on devising an evolutionary method to discover opponent models based on recurrent neural networks. A series of computer poker agents called Adaptive System for Hold’Em (ASHE) were evolved for HUNL. ASHE models the opponent explicitly using Pattern Recognition Trees (PRTs) and LSTM estimators. The default and board-texture-based PRTs maintain statistical data on the opponent strategies at different game states. The Opponent Action Rate Estimator predicts the opponent’s moves, and the Hand Range Estimator evaluates the showdown value of ASHE’s hand. Recursive Utility Estimation is used to evaluate the expected utility/reward for each available action. Experimental results show that (1) ASHE exploits opponents with high to moderate level of exploitability more effectively than Nash-equilibrium-based agents, and (2) ASHE can defeat top-ranking equilibrium-based poker agents. Thus, the dissertation introduces an effective new method to building high-performance computer agents for poker and other imperfect information games. It also provides a promising direction for future research in imperfect information games beyond the equilibrium-based approach.Computer Science

A Survey of Monte Carlo Tree Search Methods

Monte Carlo tree search (MCTS) is a recently proposed search method that combines the precision of tree search with the generality of random sampling. It has received considerable interest due to its spectacular success in the difficult problem of computer Go, but has also proved beneficial in a range of other domains. This paper is a survey of the literature to date, intended to provide a snapshot of the state of the art after the first five years of MCTS research. We outline the core algorithm's derivation, impart some structure on the many variations and enhancements that have been proposed, and summarize the results from the key game and nongame domains to which MCTS methods have been applied. A number of open research questions indicate that the field is ripe for future work

Game theoretic modeling and analysis : A co-evolutionary, agent-based approach

Ph.DDOCTOR OF PHILOSOPH

Opponent Modelling in Multi-Agent Systems

Reinforcement Learning (RL) formalises a problem where an intelligent agent needs to learn and achieve certain goals by maximising a long-term return in an environment. Multi-agent reinforcement learning (MARL) extends traditional RL to multiple agents. Many RL algorithms lose convergence guarantee in non-stationary environments due to the adaptive opponents. Partial observation caused by agents’ different private observations introduces high variance during the training which exacerbates the data inefficiency. In MARL, training an agent to perform well against a set of opponents often leads to bad performance against another set of opponents. Non-stationarity, partial observation and unclear learning objective are three critical problems in MARL which hinder agents’ learning and they all share a cause which is the lack of knowledge of the other agents. Therefore, in this thesis, we propose to solve these problems with opponent modelling methods. We tailor our solutions by combining opponent modelling with other techniques according to the characteristics of problems we face. Specifically, we first propose ROMMEO, an algorithm inspired by Bayesian inference, as a solution to alleviate the non-stationarity in cooperative games. Then we study the partial observation problem caused by agents’ private observation and design an implicit communication training method named PBL. Lastly, we investigate solutions to the non-stationarity and unclear learning objective problems in zero-sum games. We propose a solution named EPSOM which aims for finding safe exploitation strategies to play against non-stationary opponents. We verify our proposed methods by varied experiments and show they can achieve the desired performance. Limitations and future works are discussed in the last chapter of this thesis

The Computational Intelligence of MoGo Revealed in Taiwan's Computer Go Tournaments

International audienceTHE AUTHORS ARE EXTREMELY GRATEFUL TO GRID5000 for helping in designing and experimenting around Monte-Carlo Tree Search. In order to promote computer Go and stimulate further development and research in the field, the event activities, "Computational Intelligence Forum" and "World 99 Computer Go Championship," were held in Taiwan. This study focuses on the invited games played in the tournament, "Taiwanese Go players versus the computer program MoGo," held at National University of Tainan (NUTN). Several Taiwanese Go players, including one 9-Dan professional Go player and eight amateur Go players, were invited by NUTN to play against MoGo from August 26 to October 4, 2008. The MoGo program combines All Moves As First (AMAF)/Rapid Action Value Estimation (RAVE) values, online "UCT-like" values, offline values extracted from databases, and expert rules. Additionally, four properties of MoGo are analyzed including: (1) the weakness in corners, (2) the scaling over time, (3) the behavior in handicap games, and (4) the main strength of MoGo in contact fights. The results reveal that MoGo can reach the level of 3 Dan with, (1) good skills for fights, (2) weaknesses in corners, in particular for "semeai" situations, and (3) weaknesses in favorable situations such as handicap games. It is hoped that the advances in artificial intelligence and computational power will enable considerable progress in the field of computer Go, with the aim of achieving the same levels as computer chess or Chinese chess in the future