{"type":"ScholarlyArticle","title":"Conditions for Avoiding Node Re-expansions in Bounded Suboptimal Search","authors":[{"name":"Jingwei Chen","slug":"jingwei-chen","given":"Jingwei","family":"Chen","affiliation":"Department of Computing Science , University of Alberta , Edmonton , AB Canada"},{"name":"Nathan R. Sturtevant","slug":"nathan-r-sturtevant","given":"Nathan R.","family":"Sturtevant","affiliation":"Department of Computing Science , University of Alberta , Edmonton , AB Canada"}],"abstract":"Many practical problems are too difficult to solve optimally, motivating the need to found suboptimal solutions, particularly those with bounds on the final solution quality. Algorithms like Weighted A*, A*-epsilon, Optimistic Search, EES, and DPS have been developed to find suboptimal solutions with solution quality that is within a constant bound of the optimal solution. However, with the exception of weighted A*, all of these algorithms require performing node re-expansions during search. This paper explores the properties of priority functions that can find bounded suboptimal solution without requiring node re-expansions. After general bounds are developed, two new convex priority functions are developed that can outperform weighted A*.","doi":"10.24963/ijcai.2019/170","url":"https://ijcai.org/proceedings/2019/170","pdf":"https://ijcai.org/proceedings/2019/0170.pdf","markdown":"https://ijcai.org/proceedings/2019/170.md","bibtex":"https://ijcai.org/proceedings/2019/bibtex/170","volume":{"slug":"2019","title":"Proceedings of the Twenty-Eighth International Joint Conference on Artificial Intelligence","short_title":"IJCAI 2019","url":"https://ijcai.org/proceedings/2019/","year":2019,"location":"Macao","dates":"10-16 August 2019","editors":"Sarit Kraus","isbn":"978-0-9992411-4-1","publisher":"International Joint Conferences on Artificial Intelligence Organization","doi_prefix":"10.24963/ijcai.2019"},"section":"Heuristic Search and Game Playing","track":"Main track","number":170,"pages":{"first":1220,"last":1226},"keywords":["Heuristic Search and Game Playing: Combinatorial Search and Optimisation","Heuristic Search and Game Playing: Heuristic Search"],"videos":[],"references":[{"position":1,"raw":"[Benton et al., 2007] J Benton, Minh Do, and Wheeler Ruml. A simple testbed for on-line planning. In ICAPS Workshop on Moving Planning and Scheduling Systems into the Real World, 2007.","title":"A simple testbed for on-line planning","authors":"Benton","year":"2007","venue":"ICAPS Workshop on Moving Planning and Scheduling Systems into the Real World","doi":null,"url":null,"internal_url":null},{"position":2,"raw":"[Bulitko et al., 2011] Vadim Bulitko, Yngvi Björnsson, Nathan R Sturtevant, and Ramon Lawrence. Real-time heuristic search for pathfinding in video games. In Ar- tificial Intelligence for Computer Games, pages 1-30. Springer, 2011.","title":"Real-time heuristic search for pathfinding in video games","authors":"Vadim Bulitko, Yngvi Björnsson, Nathan R Sturtevant, Ramon Lawrence","year":"2011","venue":"Artificial Intelligence for Computer Games","doi":null,"url":null,"internal_url":null},{"position":3,"raw":"[Chen et al., 2019] Jingwei Chen, Nathan R. Sturtevant, William Doyle, and Wheeler Ruml. Revisiting suboptimal search. In Symposium on Combinatorial Search (SoCS), 2019.","title":"Revisiting suboptimal search","authors":"Jingwei Chen, Nathan R Sturtevant, William Doyle, Wheeler Ruml","year":"2019","venue":"Symposium on Combinatorial Search (SoCS)","doi":null,"url":null,"internal_url":null},{"position":4,"raw":"[Gilon et al., 2016] Daniel Gilon, Ariel Felner, and Roni Stern. Dynamic potential search-a new bounded sub- optimal search. In Symposium on Combinatorial Search (SoCS), 2016.","title":"Dynamic potential search-a new bounded suboptimal search","authors":"Ariel Daniel Gilon, Roni Felner, Stern","year":"2016","venue":"Symposium on Combinatorial Search (SoCS)","doi":null,"url":null,"internal_url":null},{"position":5,"raw":"[Korf, 1985] Richard E Korf. Depth-first iterative- deepening: An optimal admissible tree search. Artificial intelligence, 27(1):97-109, 1985.","title":"Depth-first iterativedeepening: An optimal admissible tree search","authors":"Richard E Korf","year":"1985","venue":"Artificial intelligence","doi":null,"url":null,"internal_url":null},{"position":6,"raw":"[Likhachev et al., 2004] Maxim Likhachev, Geoffrey J Gor- don, and Sebastian Thrun. ARA*: Anytime A* with prov- able bounds on sub-optimality. In Advances in neural in- formation processing systems, pages 767-774, 2004.","title":"ARA*: Anytime A* with provable bounds on sub-optimality","authors":"Likhachev","year":"2004","venue":"Advances in neural information processing systems","doi":null,"url":null,"internal_url":null},{"position":7,"raw":"[Pearl and Kim, 1982] Judea Pearl and Jin H. Kim. Studies in semi-admissible heuristics. IEEE Transactions on Pat- tern Analysis and Machine Intelligence, PAMI-4(4):392- 399, July 1982.","title":"Judea Pearl and Jin H. Kim. Studies in semi-admissible heuristics","authors":"Kim Pearl","year":"1982","venue":"IEEE Transactions on Pattern Analysis and Machine Intelligence","doi":null,"url":null,"internal_url":null},{"position":8,"raw":"[Pohl, 1970] Ira Pohl. Heuristic search viewed as path find- ing in a graph. Artificial intelligence, 1(3-4):193-204, 1970.","title":"Heuristic search viewed as path finding in a graph","authors":"Ira Pohl","year":"1970","venue":"Artificial intelligence","doi":null,"url":null,"internal_url":null},{"position":9,"raw":"[Pohl, 1973] Ira Pohl. The avoidance of (relative) catas- trophe, heuristic competence, genuine dynamic weight- ing and computational issues in heuristic problem solving. In Proceedings of the 3rd international joint conference on Artificial intelligence, pages 12-17.","title":"The avoidance of (relative) catastrophe, heuristic competence, genuine dynamic weighting and computational issues in heuristic problem solving","authors":"Ira Pohl","year":null,"venue":"Proceedings of the 3rd international joint conference on Artificial intelligence","doi":null,"url":null,"internal_url":null},{"position":10,"raw":"[Sepetnitsky et al., 2016] Vitaly Sepetnitsky, Ariel Felner, and Roni Stern. Repair policies for not reopening nodes in different search settings. In Ninth Annual Symposium on Combinatorial Search, 2016.","title":"Repair policies for not reopening nodes in different search settings","authors":"Vitaly Sepetnitsky, Ariel Felner, Roni Stern","year":"2016","venue":"Ninth Annual Symposium on Combinatorial Search","doi":null,"url":null,"internal_url":null},{"position":11,"raw":"[Sturtevant, 2012] Nathan R. Sturtevant. Benchmarks for grid-based pathfinding. Transactions on Computational Intelligence and AI in Games, 4(2):144-148, 2012.","title":"Benchmarks for grid-based pathfinding","authors":"Nathan R Sturtevant","year":"2012","venue":"Transactions on Computational Intelligence and AI in Games","doi":null,"url":null,"internal_url":null},{"position":12,"raw":"[Thayer and Ruml, 2008] Jordan T. Thayer and Wheeler Ruml. Faster than weighted A*: An optimistic approach to bounded suboptimal search. In International Conference on Automated Planning and Scheduling, pages 355-362, 2008.","title":"Faster than weighted A*: An optimistic approach to bounded suboptimal search","authors":"Jordan T Thayer, Wheeler Ruml","year":"2008","venue":"International Conference on Automated Planning and Scheduling","doi":null,"url":null,"internal_url":null},{"position":13,"raw":"[Thayer and Ruml, 2011] Jordan T. Thayer and Wheeler Ruml. Bounded suboptimal search: A direct approach using inadmissible estimates. In International Joint Con- ference on Artifical Intelligence (IJCAI), pages 674-679, 2011.","title":"Bounded suboptimal search: A direct approach using inadmissible estimates","authors":"Jordan T Thayer, Wheeler Ruml","year":"2011","venue":"International Joint Conference on Artifical Intelligence (IJCAI)","doi":null,"url":null,"internal_url":null},{"position":14,"raw":"[Valenzano et al., 2013] Richard Valenzano, Shahab Jabbari Arfaee, Roni Stern, Jordan Thayer, and Nathan Sturtevant. Using alternative suboptimality bounds in heuristic search. In International Conference on Automated Planning and Scheduling (ICAPS), pages 233-241, 2013.","title":"Using alternative suboptimality bounds in heuristic search","authors":"Richard Valenzano, Shahab Jabbari Arfaee, Roni Stern, Jordan Thayer, Nathan Sturtevant","year":"2013","venue":"International Conference on Automated Planning and Scheduling (ICAPS)","doi":null,"url":null,"internal_url":null},{"position":15,"raw":"[Valenzano et al., 2014] Richard Valenzano, Nathan Sturte- vant, and Jonathan Schaeffer. Worst-case solution quality analysis when not re-expanding nodes in best-first search. In AAAI Conference on Artificial Intelligence, pages 885- 892, 2014.","title":"Worst-case solution quality analysis when not re-expanding nodes in best-first search","authors":"Richard Valenzano, Nathan Sturtevant, Jonathan Schaeffer","year":"2014","venue":"AAAI Conference on Artificial Intelligence","doi":null,"url":null,"internal_url":null}],"license_note":"Copyright International Joint Conferences on Artificial Intelligence."}