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O(log log n)-competitive dynamic binary search trees

Published: 22 January 2006 Publication History

Abstract

The Dynamic Optimality Conjecture [ST85] states that splay trees are competitive (within a constant competitive factor) among the class of all binary search tree (BST) algorithms. Despite 20 years of research this conjecture is still unresolved. Recently, Demaine et al. [DHIP04] suggested searching for alternative algorithms which have small but non-constant competitive factors. They proposed Tango, a BST algorithm which is nearly dynamically optimal - its competitive ratio is O(log log n) instead of a constant. Unfortunately, for many access patterns, such as random and sequential, Tango is worse than other BST algorithms by a factor of log log n.In this paper, we introduce the multi-splay tree (MST) data structure, which is the first O(log log n)-competitive BST to simultaneously achieve O(log n) amortized cost and O(log2 n) worst-case cost per query. We also prove the sequential access lemma for MSTs, which states that sequentially accessing all keys takes linear time. Thus, MSTs are O(log log n)-competitive like Tango but, unlike Tango, require only O(log n) amortized time per access in an arbitrary sequence and only O(1) amortized time per access during a sequential access sequence.Furthermore, we generalize the standard framework for competitive analysis of BST algorithms to include updates (insertions and deletions) in addition to queries. In doing so, we extend the lower bound of Wilber [Wil89] and Demaine et al. [DHIP04] to handle these update operations. We show how MSTs can be modified to support these update operations and be O(log log n)-competitive in the new framework while maintaining the rest of the properties above.

References

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Cited By

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  • (2018)Smooth heaps and a dual view of self-adjusting data structuresProceedings of the 50th Annual ACM SIGACT Symposium on Theory of Computing10.1145/3188745.3188864(801-814)Online publication date: 20-Jun-2018
  • (2017)Practical adaptive search trees with performance boundsProceedings of the Australasian Computer Science Week Multiconference10.1145/3014812.3014836(1-8)Online publication date: 30-Jan-2017
  • (2016)SplayNetIEEE/ACM Transactions on Networking10.1109/TNET.2015.241031324:3(1421-1433)Online publication date: 1-Jun-2016
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Published In

cover image ACM Conferences
SODA '06: Proceedings of the seventeenth annual ACM-SIAM symposium on Discrete algorithm
January 2006
1261 pages
ISBN:0898716055

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Society for Industrial and Applied Mathematics

United States

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Published: 22 January 2006

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Overall Acceptance Rate 411 of 1,322 submissions, 31%

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Cited By

View all
  • (2018)Smooth heaps and a dual view of self-adjusting data structuresProceedings of the 50th Annual ACM SIGACT Symposium on Theory of Computing10.1145/3188745.3188864(801-814)Online publication date: 20-Jun-2018
  • (2017)Practical adaptive search trees with performance boundsProceedings of the Australasian Computer Science Week Multiconference10.1145/3014812.3014836(1-8)Online publication date: 30-Jan-2017
  • (2016)SplayNetIEEE/ACM Transactions on Networking10.1109/TNET.2015.241031324:3(1421-1433)Online publication date: 1-Jun-2016
  • (2012)A self-adjusting data structure for multidimensional point setsProceedings of the 20th Annual European conference on Algorithms10.1007/978-3-642-33090-2_67(778-789)Online publication date: 10-Sep-2012
  • (2012)De-amortizing binary search treesProceedings of the 39th international colloquium conference on Automata, Languages, and Programming - Volume Part I10.1007/978-3-642-31594-7_11(121-132)Online publication date: 9-Jul-2012
  • (2011)Upper bounds for maximally greedy binary search treesProceedings of the 12th international conference on Algorithms and data structures10.5555/2033190.2033225(411-422)Online publication date: 15-Aug-2011
  • (2010)An O(log log n)-competitive binary search tree with optimal worst-case access timesProceedings of the 12th Scandinavian conference on Algorithm Theory10.1007/978-3-642-13731-0_5(38-49)Online publication date: 21-Jun-2010
  • (2009)The geometry of binary search treesProceedings of the twentieth annual ACM-SIAM symposium on Discrete algorithms10.5555/1496770.1496825(496-505)Online publication date: 4-Jan-2009
  • (2008)Splay trees, Davenport-Schinzel sequences, and the deque conjectureProceedings of the nineteenth annual ACM-SIAM symposium on Discrete algorithms10.5555/1347082.1347204(1115-1124)Online publication date: 20-Jan-2008
  • (2008)Dynamic optimality for skip lists and B-treesProceedings of the nineteenth annual ACM-SIAM symposium on Discrete algorithms10.5555/1347082.1347203(1106-1114)Online publication date: 20-Jan-2008
  • Show More Cited By

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