{"type":"ScholarlyArticle","title":"Recent Progress in Heuristic Search: A Case Study of the Four-Peg Towers of Hanoi Problem","authors":[{"name":"Richard E. Korf","slug":"richard-e-korf","given":"Richard E.","family":"Korf","affiliation":""},{"name":"Ariel Felner","slug":"ariel-felner","given":"Ariel","family":"Felner","affiliation":""}],"abstract":"We integrate a number of new and recent advances in heuristic search, and apply them to the four-peg Towers of Hanoi problem. These include frontier search, disk-based search, parallel processing, multiple, compressed, disjoint, and additive pattern database heuristics, and breadth-first heuristic search. New ideas include pattern database heuristics based on multiple goal states, a method to reduce coordination among multiple parallel threads, and a method for reducing the number of heuristic calculations. We perform the first complete breadth-first searches of the 21 and 22-disc four-peg Towers of Hanoi problems, and extend the verification of presumed optimal solutions to this problem from 24 to 30 discs. Verification of the 31-disc problem is in progress.","doi":null,"url":"https://ijcai.org/proceedings/2007/374","pdf":"https://ijcai.org/proceedings/2007/0374.pdf","markdown":"https://ijcai.org/proceedings/2007/374.md","bibtex":"https://ijcai.org/proceedings/2007/bibtex/374","volume":{"slug":"2007","title":"Proceedings of the Twentieth International Joint Conference on Artificial Intelligence","short_title":"IJCAI 2007","url":"https://ijcai.org/proceedings/2007/","year":2007,"location":"Hyderabad, India","dates":"","editors":"Ramon López de Mántaras","isbn":"","publisher":"International Joint Conferences on Artificial Intelligence","doi_prefix":""},"section":null,"track":"","number":374,"pages":{"first":2324,"last":2328},"keywords":[],"videos":[],"references":[],"license_note":"Copyright International Joint Conferences on Artificial Intelligence."}