{"type":"ScholarlyArticle","title":"Best-Case and Worst-Case Behavior of Greedy Best-First Search","authors":[{"name":"Manuel Heusner","slug":"manuel-heusner","given":"Manuel","family":"Heusner","affiliation":"University of Basel , Switzerland"},{"name":"Thomas Keller","slug":"thomas-keller","given":"Thomas","family":"Keller","affiliation":"University of Basel , Switzerland"},{"name":"Malte Helmert","slug":"malte-helmert","given":"Malte","family":"Helmert","affiliation":"University of Basel , Switzerland"}],"abstract":"We study the impact of tie-breaking on the behavior of greedy best-first search with a fixed state space and fixed heuristic. We prove that it is NP-complete to determine the number of states that need to be expanded by greedy best-first search in the best case or in the worst case. However, the best- and worst-case behavior can be computed in polynomial time for undirected state spaces. We perform computational experiments on benchmark tasks from the International Planning Competitions that compare the best and worst cases of greedy best-first search to FIFO, LIFO and random tie-breaking. The experiments demonstrate the importance of tie-breaking in greedy best-first search.","doi":"10.24963/ijcai.2018/203","url":"https://ijcai.org/proceedings/2018/203","pdf":"https://ijcai.org/proceedings/2018/0203.pdf","markdown":"https://ijcai.org/proceedings/2018/203.md","bibtex":"https://ijcai.org/proceedings/2018/bibtex/203","volume":{"slug":"2018","title":"Proceedings of the Twenty-Seventh International Joint Conference on Artificial Intelligence","short_title":"IJCAI 2018","url":"https://ijcai.org/proceedings/2018/","year":2018,"location":"Stockholm","dates":"13-19 July 2018","editors":"Jérôme Lang","isbn":"978-0-9992411-2-7","publisher":"International Joint Conferences on Artificial Intelligence Organization","doi_prefix":"10.24963/ijcai.2018"},"section":"Heuristic Search and Game Playing","track":"Main track","number":203,"pages":{"first":1463,"last":1470},"keywords":["Heuristic Search and Game Playing: Heuristic Search"],"videos":[],"references":[{"position":1,"raw":"[Asai and Fukunaga, 2017] Masataro Asai and Alex Fuku- naga. Exploration among and within plateaus in greedy best-first search. In Proceedings of the Twenty-Seventh International Conference on Automated Planning and Scheduling (ICAPS 2017), pages 11-19. AAAI Press, 2017.","title":"Masataro Asai and Alex Fukunaga. Exploration among and within plateaus in greedy best-first search","authors":"Fukunaga Asai","year":"2017","venue":"Proceedings of the Twenty-Seventh International Conference on Automated Planning and Scheduling (ICAPS 2017)","doi":null,"url":null,"internal_url":null},{"position":2,"raw":"[Dechter and Pearl, 1985] Rina Dechter and Judea Pearl. Generalized best-first search strategies and the optimality of A * . Journal of the ACM, 32(3):505-536, 1985.","title":"Generalized best-first search strategies and the optimality of A","authors":"Rina Dechter, Judea Pearl","year":"1985","venue":"Journal of the ACM","doi":null,"url":null,"internal_url":null},{"position":3,"raw":"[Doran and Michie, 1966] James E. Doran and Donald Michie. Experiments with the graph traverser program. Proceedings of the Royal Society A, 294:235-259, 1966.","title":"Experiments with the graph traverser program","authors":"James E Doran, Donald Michie","year":"1966","venue":"Proceedings of the Royal Society A","doi":null,"url":null,"internal_url":null},{"position":4,"raw":"[Garey and Johnson, 1979] Michael R. Garey and David S. Johnson. Computers and Intractability -A Guide to the Theory of NP-Completeness. Freeman, 1979. [Helmert and Röger, 2008] Malte Helmert and Gabriele Röger. How good is almost perfect? In Proceedings of the Twenty-Third AAAI Conference on Artificial Intelligence (AAAI 2008), pages 944-949. AAAI Press, 2008.","title":"Computers and Intractability -A Guide to the Theory of NP-Completeness","authors":"Michael R Garey, David S Johnson ; Freeman, ; Helmert, Röger, Malte Helmert, Gabriele Röger","year":"1979","venue":"Proceedings of the Twenty-Third AAAI Conference on Artificial Intelligence (AAAI 2008)","doi":null,"url":null,"internal_url":null},{"position":5,"raw":"[Helmert, 2006] Malte Helmert. The Fast Downward plan- ning system. Journal of Artificial Intelligence Research, 26:191-246, 2006.","title":"The Fast Downward planning system","authors":"Malte Helmert","year":"2006","venue":"Journal of Artificial Intelligence Research","doi":null,"url":null,"internal_url":null},{"position":6,"raw":"[Heusner et al., 2017] Manuel Heusner, Thomas Keller, and Malte Helmert. Understanding the search behaviour of greedy best-first search. In Alex Fukunaga and Akihiro Kishimoto, editors, Proceedings of the 10th Annual Sym- posium on Combinatorial Search (SoCS 2017), pages 47- 55. AAAI Press, 2017.","title":"Understanding the search behaviour of greedy best-first search","authors":"Manuel Heusner, Thomas Keller, Malte Helmert","year":"2017","venue":"Proceedings of the 10th Annual Symposium on Combinatorial Search (SoCS 2017)","doi":null,"url":null,"internal_url":null},{"position":7,"raw":"[Hoffmann and Nebel, 2001] Jörg Hoffmann and Bernhard Nebel. The FF planning system: Fast plan generation through heuristic search. Journal of Artificial Intelligence Research, 14:253-302, 2001.","title":"The FF planning system: Fast plan generation through heuristic search","authors":"Nebel Hoffmann, Jörg Hoffmann, Bernhard Nebel","year":"2001","venue":"Journal of Artificial Intelligence Research","doi":null,"url":null,"internal_url":null},{"position":8,"raw":"[Hoffmann, 2005] Jörg Hoffmann. Where 'ignoring delete lists' works: Local search topology in planning bench- marks. Journal of Artificial Intelligence Research, 24:685- 758, 2005.","title":"Where 'ignoring delete lists' works: Local search topology in planning benchmarks","authors":"Jörg Hoffmann, Hoffmann","year":"2005","venue":"Journal of Artificial Intelligence Research","doi":null,"url":null,"internal_url":null},{"position":9,"raw":"[Holte, 2010] Robert C. Holte. Common misconceptions concerning heuristic search. In Ariel Felner and Nathan Sturtevant, editors, Proceedings of the Third Annual Sym- posium on Combinatorial Search (SoCS 2010), pages 46- 51. AAAI Press, 2010.","title":"Common misconceptions concerning heuristic search","authors":"C Robert, Holte","year":"2010","venue":"Proceedings of the Third Annual Symposium on Combinatorial Search (SoCS 2010)","doi":null,"url":null,"internal_url":null},{"position":10,"raw":"[Korf et al., 2001] Richard E. Korf, Michael Reid, and Ste- fan Edelkamp. Time complexity of iterative-deepening A * . Artificial Intelligence, 129:199-218, 2001.","title":"Time complexity of iterative-deepening A","authors":"Richard E Korf, Michael Reid, Stefan Edelkamp","year":"2001","venue":"Artificial Intelligence","doi":null,"url":null,"internal_url":null},{"position":11,"raw":"[Lawler, 1976] Eugene L. Lawler. Combinatorial Optimiza- tion: Networks and Matroids. Holt, Rinehart and Winston, 1976.","title":"Combinatorial Optimization: Networks and Matroids","authors":"Eugene L Lawler","year":"1976","venue":null,"doi":null,"url":null,"internal_url":null},{"position":12,"raw":"[Martelli, 1977] Alberto Martelli. On the complexity of ad- missible search algorithms. Artificial Intelligence, 8:1-13, 1977.","title":"On the complexity of admissible search algorithms","authors":"Alberto Martelli","year":"1977","venue":"Artificial Intelligence","doi":null,"url":null,"internal_url":null},{"position":13,"raw":"[Pearl, 1984] Judea Pearl. Heuristics: Intelligent Search Strategies for Computer Problem Solving. Addison- Wesley, 1984.","title":"Judea Pearl. Heuristics: Intelligent Search Strategies for Computer Problem Solving","authors":"Pearl","year":"1984","venue":null,"doi":null,"url":null,"internal_url":null},{"position":14,"raw":"[Wilt and Ruml, 2014] Christopher Wilt and Wheeler Ruml. Speedy versus greedy search. In Stefan Edelkamp and Ro- man Barták, editors, Proceedings of the Seventh Annual Symposium on Combinatorial Search (SoCS 2014), pages 184-192. AAAI Press, 2014.","title":"Christopher Wilt and Wheeler Ruml. Speedy versus greedy search","authors":"Ruml Wilt","year":"2014","venue":"Proceedings of the Seventh Annual Symposium on Combinatorial Search (SoCS 2014)","doi":null,"url":null,"internal_url":null},{"position":15,"raw":"[Wilt and Ruml, 2015] Christopher Wilt and Wheeler Ruml. Building a heuristic for greedy search. In Levi Lelis and Roni Stern, editors, Proceedings of the Eighth Annual Symposium on Combinatorial Search (SoCS 2015), pages 131-139. AAAI Press, 2015.","title":"Building a heuristic for greedy search","authors":"Ruml ; Wilt, Christopher Wilt, Wheeler Ruml","year":"2015","venue":"Proceedings of the Eighth Annual Symposium on Combinatorial Search (SoCS 2015)","doi":null,"url":null,"internal_url":null},{"position":16,"raw":"[Wilt and Ruml, 2016] Christopher Wilt and Wheeler Ruml. Effective heuristics for suboptimal best-first search. Jour- nal of Artificial Intelligence Research, 57:273-306, 2016.","title":"Effective heuristics for suboptimal best-first search","authors":"Ruml ; Wilt, Christopher Wilt, Wheeler Ruml","year":"2016","venue":"Journal of Artificial Intelligence Research","doi":null,"url":null,"internal_url":null}],"license_note":"Copyright International Joint Conferences on Artificial Intelligence."}