Technical - Partner Event

AI Seminar – Levi Lelis

July 23, 2021 - July 23, 2021
12:00 PM – 1:00 PM MST


Title: Policy and Heuristic-Guided Tree Search Algorithms
Speaker: Levi Lelis, University of Alberta

Abstract: Heuristic search algorithms such as A* use a heuristic function to guide its search by focusing on states that are estimated to be closer to a goal state. In this talk we will explore the use of a policy, i.e., a probability distribution over actions, for solving single-agent deterministic problems. I will start by describing Levin tree search, an algorithm that uses a policy and offers guarantees on the number of nodes it needs to expand to solve state-space search problems. We will then discuss Policy-Guided Heuristic Search (PHS), a search algorithm that uses both a policy and a heuristic function to guide its search. PHS also offers guarantees on the number of nodes it needs to expand to solve search problems. I will then present empirical results showing the advantages of policy-guided tree search algorithms, especially when it is difficult to learn effective heuristic functions to guide the search.

Bio: Levi is an Assistant Professor in the Department of Computing Science at the University of Alberta and a Professor on leave from the Universidade Federal de Viçosa in Brazil. He received his Ph.D. in Computing Science in 2013 from the University of Alberta, studying under the supervision of Robert Holte (Amii Fellow and founding researcher) and Sandra Zilles. Levi has co-authored more than 45 refereed papers at venues such as the International Joint Conference on Artificial Intelligence (IJCAI), the conference for the Association for the Advancement of Artificial Intelligence (AAAI) and the Neural Information Processing Systems (NeurIPS) Conference. He has also served as a Senior Program Committee Member for IJCAI (where he received the honour of being the Distinguished Program Committee Member in 2018 and 2019) and AAAI and Program Committee Member for the Conference on Artificial Intelligence and Interactive Digital Entertainment (AIIDE). In 2020, he was also named a CIFAR CCAI Chair.

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