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Learning, planning, and representing knowledge at multiple levels of temporal abstraction are key, longstanding challenges for AI. In this paper we consider how these challenges can be addressed within the mathematical framework of reinforcement learning and Markov decision processes (MDPs). We extend the usual notion of action in this framework to include(More)
In this paper we report the set-up and results of the Multimodal Brain Tumor Image Segmentation Benchmark (BRATS) organized in conjunction with the MICCAI 2012 and 2013 conferences. Twenty state-of-the-art tumor segmentation algorithms were applied to a set of 65 multi-contrast MR scans of low- and high-grade glioma patients-manually annotated by up to four(More)
Eligibility traces have been shown to speed reinforcement learning, to make it more robust to hidden states, and to provide a link between Monte Carlo and temporal-difference methods. Here we generalize eligibility traces to off-policy learning, in which one learns about a policy different from the policy that generates the data. Off-policy methods can(More)
TEMPORAL ABSTRACTION IN REINFORCEMENT LEARNING MAY 2000 DOINA PRECUP B.S ., TECHNICAL UNIVERSITY CLUJ-NAPOCA, ROMANIA M.S ., UNIVERSITY OF MASSACHUSETTS, AMHERST Ph.D., UNIVERSITY OF MASSACHUSETTS AMHERST Dire ted by: Professor Ri hard S. Sutton De ision making usually involves hoosing among di erent ourses of a tion over a broad range of time s ales. For(More)
We address the problem of automatically constructing basis functions for linear approximation of the value function of a Markov Decision Process (MDP). Our work builds on results by Bertsekas and Castañon (1989) who proposed a method for automatically aggregating states to speed up value iteration. We propose to use neighborhood component analysis(More)
In this paper, we advocate the use of Sparse Distributed Memories (SDMs) for on-line, value-based reinforcement learning (RL). SDMs provide a linear, local function approximation scheme, designed to work when a very large/ high-dimensional input (address) space has to be mapped into a much smaller physical memory. We present an implementation of the SDM(More)
Maintaining accurate world knowledge in a complex and changing environment is a perennial problem for robots and other artificial intelligence systems. Our architecture for addressing this problem, called Horde, consists of a large number of independent reinforcement learning sub-agents, or demons. Each demon is responsible for answering a single predictive(More)
We introduce the first temporal-difference learning algorithms that converge with smooth value function approximators, such as neural networks. Conventional temporal-difference (TD) methods, such as TD(λ), Q-learning and Sarsa have been used successfully with function approximation in many applications. However, it is well known that off-policy sampling, as(More)
Learning, planning, and representing knowledge at multiple levels of temporal abstraction are key challenges for AI. In this paper we develop an approach to these problems based on the mathematical framework of reinforcement learning and Markov decision processes (MDPs). We extend the usual notion of action to include options—whole courses of behavior that(More)