{"type":"ScholarlyArticle","title":"K∗ Search over Orbit Space for Top-k Planning","authors":[{"name":"Michael Katz","slug":"michael-katz","given":"Michael","family":"Katz","affiliation":"IBM T.J. Watson Research Center , Yorktown Heights , USA"},{"name":"Junkyu Lee","slug":"junkyu-lee","given":"Junkyu","family":"Lee","affiliation":"IBM T.J. Watson Research Center , Yorktown Heights , USA"}],"abstract":"Top-k planning, the task of finding k top-cost plans, is a key formalism for many planning applications and K* search is a well-established approach to top-k planning.  The algorithm iteratively runs A* search and Eppstein’s algorithm until a sufficient number of plans is found.  The performance of K* algorithm is therefore inherently limited by the performance of A*, and in order to improve K* performance, that of A* must be improved.  In cost-optimal planning, orbit space search improves A* performance by exploiting symmetry pruning, essentially performing A* in the orbit space instead of state space.  In this work, we take a similar approach to top-k planning.  We show theoretical equivalence between the goal paths in the state space and in the orbit space, allowing to perform K* search in the orbit space instead, reconstructing plans from the found paths in the orbit space.  We prove that our algorithm is sound and complete for top-k planning and empirically show it to achieve state-of-the-art performance, overtaking all existing to date top-k planners.  The code is available at https://github.com/IBM/kstar.","doi":"10.24963/ijcai.2023/596","url":"https://ijcai.org/proceedings/2023/596","pdf":"https://ijcai.org/proceedings/2023/0596.pdf","markdown":"https://ijcai.org/proceedings/2023/596.md","bibtex":"https://ijcai.org/proceedings/2023/bibtex/596","volume":{"slug":"2023","title":"Proceedings of the Thirty-Second International Joint Conference on Artificial Intelligence","short_title":"IJCAI 2023","url":"https://ijcai.org/proceedings/2023/","year":2023,"location":"Macao, SAR","dates":"19-25 August 2023","editors":"Edith Elkind","isbn":"978-1-956792-03-4","publisher":"International Joint Conferences on Artificial Intelligence Organization","doi_prefix":"10.24963/ijcai.2023"},"section":"Planning and Scheduling","track":"Main Track","number":596,"pages":{"first":5368,"last":5376},"keywords":["Planning and Scheduling: PS: Search in planning and scheduling","Planning and Scheduling: PS: Planning algorithms","Planning and Scheduling: PS: Theoretical foundations of planning"],"videos":[],"references":[{"position":1,"raw":"[Aljazzar and Leue, 2011] Husain Aljazzar and Stefan Leue. 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