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214
Dynamic Programming for Partially Observable Stochastic Games
 IN PROCEEDINGS OF THE NINETEENTH NATIONAL CONFERENCE ON ARTIFICIAL INTELLIGENCE
, 2004
"... We develop an exact dynamic programming algorithm for partially observable stochastic games (POSGs). The algorithm is a synthesis of dynamic programming for partially observable Markov decision processes (POMDPs) and iterated elimination of dominated strategies in normal form games. ..."
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Cited by 119 (23 self)
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We develop an exact dynamic programming algorithm for partially observable stochastic games (POSGs). The algorithm is a synthesis of dynamic programming for partially observable Markov decision processes (POMDPs) and iterated elimination of dominated strategies in normal form games.
Nash QLearning for GeneralSum Stochastic Games
 JOURNAL OF MACHINE LEARNING RESEARCH
, 2003
"... We extend Qlearning to a noncooperative multiagent context, using the framework of generalsum stochastic games. A learning agent maintains Qfunctions over joint actions, and performs updates based on assuming Nash equilibrium behavior over the current Qvalues. This learning protocol provably conv ..."
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Cited by 108 (0 self)
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We extend Qlearning to a noncooperative multiagent context, using the framework of generalsum stochastic games. A learning agent maintains Qfunctions over joint actions, and performs updates based on assuming Nash equilibrium behavior over the current Qvalues. This learning protocol provably converges given certain restrictions on the stage games (defined by Qvalues) that arise during learning. Experiments with a pair of twoplayer grid games suggest that such restrictions on the game structure are not necessarily required. Stage games encountered during learning in both grid environments violate the conditions. However, learning consistently converges in the first grid game, which has a unique equilibrium Qfunction, but sometimes fails to converge in the second, which has three different equilibrium Qfunctions. In a comparison of offline learning performance in both games, we find agents are more likely to reach a joint optimal path with Nash Qlearning than with a singleagent Qlearning method. When at least one agent adopts Nash Qlearning, the performance of both agents is better than using singleagent Qlearning. We have also implemented an online version of Nash Qlearning that balances exploration with exploitation, yielding improved performance.
AWESOME: A general multiagent learning algorithm that converges in selfplay and learns a best response against stationary opponents
, 2003
"... A satisfactory multiagent learning algorithm should, at a minimum, learn to play optimally against stationary opponents and converge to a Nash equilibrium in selfplay. The algorithm that has come closest, WoLFIGA, has been proven to have these two properties in 2player 2action repeated games— as ..."
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Cited by 81 (5 self)
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A satisfactory multiagent learning algorithm should, at a minimum, learn to play optimally against stationary opponents and converge to a Nash equilibrium in selfplay. The algorithm that has come closest, WoLFIGA, has been proven to have these two properties in 2player 2action repeated games— assuming that the opponent’s (mixed) strategy is observable. In this paper we present AWESOME, the first algorithm that is guaranteed to have these two properties in all repeated (finite) games. It requires only that the other players ’ actual actions (not their strategies) can be observed at each step. It also learns to play optimally against opponents that eventually become stationary. The basic idea behind AWESOME (Adapt When Everybody is Stationary, Otherwise Move to Equilibrium) is to try to adapt to the others’ strategies when they appear stationary, but otherwise to retreat to a precomputed equilibrium strategy. The techniques used to prove the properties of AWESOME are fundamentally different from those used for previous algorithms, and may help in analyzing other multiagent learning algorithms also.
An application of reinforcement learning to aerobatic helicopter flight
 In Advances in Neural Information Processing Systems 19
, 2007
"... Autonomous helicopter flight is widely regarded to be a highly challenging control problem. This paper presents the first successful autonomous completion on a real RC helicopter of the following four aerobatic maneuvers: forward flip and sideways roll at low speed, tailin funnel, and nosein funne ..."
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Cited by 73 (8 self)
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Autonomous helicopter flight is widely regarded to be a highly challenging control problem. This paper presents the first successful autonomous completion on a real RC helicopter of the following four aerobatic maneuvers: forward flip and sideways roll at low speed, tailin funnel, and nosein funnel. Our experimental results significantly extend the state of the art in autonomous helicopter flight. We used the following approach: First we had a pilot fly the helicopter to help us find a helicopter dynamics model and a reward (cost) function. Then we used a reinforcement learning (optimal control) algorithm to find a controller that is optimized for the resulting model and reward function. More specifically, we used differential dynamic programming (DDP), an extension of the linear quadratic regulator (LQR). 1
Using relative novelty to identify useful temporal abstractions in reinforcement learning
 In Proceedings of the TwentyFirst International Conference on Machine Learning
, 2004
"... We present a new method for automatically creating useful temporal abstractions in reinforcement learning. We argue that states that allow the agent to transition to a different region of the state space are useful subgoals, and propose a method for identifying them using the concept of relative nov ..."
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Cited by 68 (12 self)
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We present a new method for automatically creating useful temporal abstractions in reinforcement learning. We argue that states that allow the agent to transition to a different region of the state space are useful subgoals, and propose a method for identifying them using the concept of relative novelty. When such a state is identified, a temporallyextended activity (e.g., an option) is generated that takes the agent efficiently to this state. We illustrate the utility of the method in a number of tasks. 1.
Exploration and apprenticeship learning in reinforcement learning
 in Proc. 21st International Conference on Machine Learning
, 2005
"... We consider reinforcement learning in systems with unknown dynamics. Algorithms such as E 3 (Kearns and Singh, 2002) learn nearoptimal policies by using “exploration policies ” to drive the system towards poorly modeled states, so as to encourage exploration. But this makes these algorithms impract ..."
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Cited by 67 (2 self)
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We consider reinforcement learning in systems with unknown dynamics. Algorithms such as E 3 (Kearns and Singh, 2002) learn nearoptimal policies by using “exploration policies ” to drive the system towards poorly modeled states, so as to encourage exploration. But this makes these algorithms impractical for many systems; for example, on an autonomous helicopter, overly aggressive exploration may well result in a crash. In this paper, we consider the apprenticeship learning setting in which a teacher demonstration of the task is available. We show that, given the initial demonstration, no explicit exploration is necessary, and we can attain nearoptimal performance (compared to the teacher) simply by repeatedly executing “exploitation policies ” that try to maximize rewards. In finitestate MDPs, our algorithm scales polynomially in the number of states; in continuousstate linear dynamical systems, it scales polynomially in the dimension of the state. These results are proved using a martingale construction over relative losses. 1.
A theoretical analysis of modelbased interval estimation
 Proceedings of the Twentysecond International Conference on Machine Learning (ICML05
, 2005
"... Several algorithms for learning nearoptimal policies in Markov Decision Processes have been analyzed and proven efficient. Empirical results have suggested that Modelbased Interval Estimation (MBIE) learns efficiently in practice, effectively balancing exploration and exploitation. This paper pres ..."
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Cited by 62 (9 self)
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Several algorithms for learning nearoptimal policies in Markov Decision Processes have been analyzed and proven efficient. Empirical results have suggested that Modelbased Interval Estimation (MBIE) learns efficiently in practice, effectively balancing exploration and exploitation. This paper presents the first theoretical analysis of MBIE, proving its efficiency even under worstcase conditions. The paper also introduces a new performance metric, average loss, and relates it to its less “online ” cousins from the literature. 1.
Correlated Qlearning
 In Proceedings of the Twentieth International Conference on Machine Learning
, 2003
"... There have been several attempts to design multiagent Qlearning algorithms capable of learning equilibrium policies in generalsum Markov games, just as Qlearning learns optimal policies in Markov decision processes. We introduce correlated Qlearning, one such algorithm based on the correlated eq ..."
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Cited by 56 (2 self)
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There have been several attempts to design multiagent Qlearning algorithms capable of learning equilibrium policies in generalsum Markov games, just as Qlearning learns optimal policies in Markov decision processes. We introduce correlated Qlearning, one such algorithm based on the correlated equilibrium solution concept. Motivated by a fixed point proof of the existence of stationary correlated equilibrium policies in Markov games, we present a generic multiagent Qlearning algorithm of which many popular algorithms are immediate special cases. We also prove that certain variants of correlated (and Nash) Qlearning are guaranteed to converge to stationary correlated (and Nash) equilibrium policies in two special classes of Markov games, namely zerosum and commoninterest. Finally, we show empirically that correlated Qlearning outperforms Nash Qlearning, further justifying the former beyond noting that it is less computationally expensive than the latter.