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Theoretical Computer Science
Volume 299, Issues 1-3, 18 April 2003, Pages 231-271
 
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doi:10.1016/S0304-3975(02)00318-3    How to Cite or Link Using DOI (Opens New Window)
Copyright © 2002 Elsevier Science B.V. All rights reserved.

Fringe analysis of synchronized parallel insertion algorithms in 2–3 Trees*1

R. Baeza-YatesCorresponding Author Contact Information, E-mail The Corresponding Author, a, J. Gabarrób and X. Messeguerb

a Departamento de Ciencias de la Computación, Universidad de Chile, 2120 Blanco Encalada, Santiago, Chile b Dep. LSI, Universitat Politècnica de Catalunya, Barcelona, Spain

Received 24 May 2001; 
accepted 15 March 2002;
Communicated by W. Szpankowski 
Available online 3 June 2002.

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Abstract

Fringe analysis uses the distribution of bottom subtrees or fringe of search trees under the assumption of random insertion of keys, yielding an average case analysis of the fringe. The results in the fringe give upper and lower bounds for several measures for the whole tree.

We are interested in the fringe analysis of the synchronized parallel insertion algorithms of Paul, Vishkin, and Wagener (Image ) on 2–3 trees. This algorithm inserts k keys with k processors into a tree of size n with time O(log n+log k). As the direct analysis of this algorithm is very difficult we tackle this problem by introducing a new family of algorithms, denoted by Image algorithms, and our main theorem proves that two algorithms of this family, denoted Image and Image , bound the behavior of the fringe in the Image algorithm.

Previous work deals with the fringe analysis of sequential algorithms, but this type of analysis was still an open problem for parallel algorithms on search trees. We extend fringe analysis to parallel algorithms and we get a rich mathematical structure giving new interpretations even in the sequential case. We prove that random insertion of keys generates a binomial distribution, that the synchronized insertion of keys can be modeled by a Markov chain, and that the coefficients of the transition matrix of the Markov chain are related to the expected local behavior of our algorithm. Finally, we show that the coefficients of the power expansion of this matrix over (n+1)−1 are the binomial transform of the expected local behavior of the algorithm. We finally show that the fringe of the Image algorithm asymptotically converges to the sequential case.

Author Keywords: Fringe analysis; Parallel algorithms; 2–3 Trees; Binomial transform


 
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