{"type":"ScholarlyArticle","title":"Dual Lookups in Pattern Databases","authors":[{"name":"Ariel Felner","slug":"ariel-felner","given":"Ariel","family":"Felner","affiliation":""},{"name":"Uzi Zahavi","slug":"uzi-zahavi","given":"Uzi","family":"Zahavi","affiliation":""},{"name":"Jonathan Schaeffer","slug":"jonathan-schaeffer","given":"Jonathan","family":"Schaeffer","affiliation":""},{"name":"Robert C. Holte","slug":"robert-c-holte","given":"Robert C.","family":"Holte","affiliation":""}],"abstract":"A pattern database (PDB) is a heuristic function stored as a lookup table. Symmetries of a state space are often used to enable multiple values to be looked up in a PDB for a given state. This paper introduces an additional PDB lookup, called the dual PDB lookup. A dual PDB lookup is always admissible but can return inconsistent values. The paper also presents an extension of the well-known pathmax method so that inconsistencies in heuristic values are propagated in both directions (childto-parent, and parent-to-child) in the search tree. Experiments show that the addition of dual lookups and bidirectional pathmax propagation can reduce the number of nodes generated by IDA* by over one order of magnitude in the TopSpin puzzle and Rubik’s Cube, and by about a factor of two for the sliding tile puzzles.","doi":null,"url":"https://ijcai.org/proceedings/2005/12","pdf":"https://ijcai.org/proceedings/2005/0012.pdf","markdown":"https://ijcai.org/proceedings/2005/12.md","bibtex":"https://ijcai.org/proceedings/2005/bibtex/12","volume":{"slug":"2005","title":"Proceedings of the Nineteenth International Joint Conference on Artificial Intelligence","short_title":"IJCAI 2005","url":"https://ijcai.org/proceedings/2005/","year":2005,"location":"Edinburgh, Scotland, UK","dates":"","editors":"","isbn":"","publisher":"International Joint Conferences on Artificial Intelligence","doi_prefix":""},"section":null,"track":"","number":12,"pages":{"first":103,"last":107},"keywords":[],"videos":[],"references":[],"license_note":"Copyright International Joint Conferences on Artificial Intelligence."}