A* with Lookahead Re-Evaluated

Zhaoxing Bu; Roni Stern; Ariel Felner; Robert C. Holte

A* with Lookahead Re-Evaluated

Zhaoxing Bu
, Roni Stern
, Ariel Felner
, Robert C. Holte

University of Alberta
Ben-Gurion University of the Negev

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution › peer-review

5 Scopus citations

Abstract

A* with lookahead (AL*) is a variant of A* that performs a cost-bounded DFS lookahead from a node when it is generated. We show that the original version of AL* (AL^∗ ₀) can, in some circumstances, fail to return an optimal solution because of the move pruning it does. We present two new versions, AL^∗ ₁ and ELH, that we prove to always be correct and give conditions in which AL^∗ ₀ is guaranteed to be correct. In our experiments with unit costs, AL^∗ ₀ was usually the fastest AL* version, but its advantage was usually small. In our experiments with non-unit costs, AL^∗ ₀ substantially outperforms both A* and IDA*. We also evaluate the idea of immediately expanding a generated node if it has the same f-value as its parent. We find that doing so causes AL* to require more memory and sometimes slows AL* down.

Original language	English
Title of host publication	Proceedings of the 7th Annual Symposium on Combinatorial Search, SoCS 2014
Editors	Stefan Edelkamp, Roman Bartak
Publisher	AAAI press
Pages	44-52
Number of pages	9
ISBN (Electronic)	9781577356769
State	Published - 2014
Externally published	Yes
Event	7th Annual Symposium on Combinatorial Search, SoCS 2014 - Prague, Czech Republic Duration: 15 Aug 2014 → 17 Aug 2014

Publication series

Name	Proceedings of the 7th Annual Symposium on Combinatorial Search, SoCS 2014
Volume	2014-January

Conference

Conference	7th Annual Symposium on Combinatorial Search, SoCS 2014
Country/Territory	Czech Republic
City	Prague
Period	15/08/14 → 17/08/14

Bibliographical note

Publisher Copyright:
Copyright © 2014, Association for the Advancement of Artificial Intelligence (www.aaai.org). All rights reserved.

Cite this

@inproceedings{000411ece70840a98269f62729e2e837,

title = "A* with Lookahead Re-Evaluated",

abstract = "A* with lookahead (AL*) is a variant of A* that performs a cost-bounded DFS lookahead from a node when it is generated. We show that the original version of AL* (AL∗ 0) can, in some circumstances, fail to return an optimal solution because of the move pruning it does. We present two new versions, AL∗ 1 and ELH, that we prove to always be correct and give conditions in which AL∗ 0 is guaranteed to be correct. In our experiments with unit costs, AL∗ 0 was usually the fastest AL* version, but its advantage was usually small. In our experiments with non-unit costs, AL∗ 0 substantially outperforms both A* and IDA*. We also evaluate the idea of immediately expanding a generated node if it has the same f-value as its parent. We find that doing so causes AL* to require more memory and sometimes slows AL* down.",

author = "Zhaoxing Bu and Roni Stern and Ariel Felner and Holte, \{Robert C.\}",

note = "Publisher Copyright: Copyright {\textcopyright} 2014, Association for the Advancement of Artificial Intelligence (www.aaai.org). All rights reserved.; 7th Annual Symposium on Combinatorial Search, SoCS 2014 ; Conference date: 15-08-2014 Through 17-08-2014",

year = "2014",

language = "אנגלית",

series = "Proceedings of the 7th Annual Symposium on Combinatorial Search, SoCS 2014",

publisher = "AAAI press",

pages = "44--52",

editor = "Stefan Edelkamp and Roman Bartak",

booktitle = "Proceedings of the 7th Annual Symposium on Combinatorial Search, SoCS 2014",

}

Bu, Z, Stern, R, Felner, A & Holte, RC 2014, A* with Lookahead Re-Evaluated. in S Edelkamp & R Bartak (eds), Proceedings of the 7th Annual Symposium on Combinatorial Search, SoCS 2014. Proceedings of the 7th Annual Symposium on Combinatorial Search, SoCS 2014, vol. 2014-January, AAAI press, pp. 44-52, 7th Annual Symposium on Combinatorial Search, SoCS 2014, Prague, Czech Republic, 15/08/14.

A* with Lookahead Re-Evaluated. / Bu, Zhaoxing; Stern, Roni; Felner, Ariel et al.
Proceedings of the 7th Annual Symposium on Combinatorial Search, SoCS 2014. ed. / Stefan Edelkamp; Roman Bartak. AAAI press, 2014. p. 44-52 (Proceedings of the 7th Annual Symposium on Combinatorial Search, SoCS 2014; Vol. 2014-January).

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution › peer-review

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A* with Lookahead Re-Evaluated

Abstract

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Conference

Bibliographical note

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