scholarly journals The variance for partial match retrievals in $k$-dimensional bucket digital trees

2010 ◽  
Vol DMTCS Proceedings vol. AM,... (Proceedings) ◽  
Author(s):  
Michael Fuchs
Keyword(s):  
Search Trees ◽  
Partial Match ◽  
Digital Trees ◽  
Digital Search Trees ◽  
International Audience ◽  
Digital Search

International audience The variance of partial match queries in $k$-dimensional tries was investigated in a couple of papers in the mid-nineties, the resulting analysis being long and complicated. In this paper, we are going to re-derive these results with a much easier approach. Moreover, our approach works for $k$-dimensional PATRICIA tries, $k$-dimensional digital search trees and bucket versions as well.

scholarly journals Distribution of inter-node distances in digital trees

2005 ◽  
Vol DMTCS Proceedings vol. AD,... (Proceedings) ◽  
Author(s):  
Rafik Aguech ◽  
Nabil Lasmar ◽  
Hosam Mahmoud
Keyword(s):  
Fixed Point ◽  
Mellin Transform ◽  
Search Trees ◽  
Digital Trees ◽  
Digital Search Trees ◽  
Point Solution ◽  
Fixed Point Equation ◽  
International Audience ◽  
Bounded Variance ◽  
Digital Search

International audience We investigate distances between pairs of nodes in digital trees (digital search trees (DST), and tries). By analytic techniques, such as the Mellin Transform and poissonization, we describe a program to determine the moments of these distances. The program is illustrated on the mean and variance. One encounters delayed Mellin transform equations, which we solve by inspection. Interestingly, the unbiased case gives a bounded variance, whereas the biased case gives a variance growing with the number of keys. It is therefore possible in the biased case to show that an appropriately normalized version of the distance converges to a limit. The complexity of moment calculation increases substantially with each higher moment; A shortcut to the limit is needed via a method that avoids the computation of all moments. Toward this end, we utilize the contraction method to show that in biased digital search trees the distribution of a suitably normalized version of the distances approaches a limit that is the fixed-point solution (in the Wasserstein space) of a distributional equation. An explicit solution to the fixed-point equation is readily demonstrated to be Gaussian.

scholarly journals Digital search trees with m trees: Level polynomials and insertion costs

2011 ◽  
Vol Vol. 13 no. 3 (Analysis of Algorithms) ◽  
Author(s):  
Helmut Prodinger
Keyword(s):  
Analysis Of Algorithms ◽  
Approximate Counting ◽  
Search Trees ◽  
Digital Search Trees ◽  
International Audience ◽  
Digital Search

Analysis of Algorithms International audience We adapt a novel idea of Cichon's related to Approximate Counting to the present instance of Digital Search Trees, by using m (instead of one) such trees. We investigate the level polynomials, which have as coefficients the expected numbers of data on a given level, and the insertion costs. The level polynomials can be precisely described, thanks to formulae from q-analysis. The asymptotics of expectation and variance of the insertion cost are fairly standard these days and done with Rice's method.

scholarly journals Asymptotic variance of random symmetric digital search trees

2010 ◽  
Vol Vol. 12 no. 2 ◽  
Author(s):  
Hsien-Kuei Hwang ◽  
Michael Fuchs ◽  
Vytas Zacharovas
Keyword(s):  
Generating Functions ◽  
Asymptotic Variance ◽  
Shape Parameters ◽  
Search Trees ◽  
New Approach ◽  
Total Path Length ◽  
Digital Search Trees ◽  
Combined Use ◽  
International Audience ◽  
Digital Search

Dedicated to the 60th birthday of Philippe Flajolet International audience Asymptotics of the variances of many cost measures in random digital search trees are often notoriously messy and involved to obtain. A new approach is proposed to facilitate such an analysis for several shape parameters on random symmetric digital search trees. Our approach starts from a more careful normalization at the level of Poisson generating functions, which then provides an asymptotically equivalent approximation to the variance in question. Several new ingredients are also introduced such as a combined use of the Laplace and Mellin transforms and a simple, mechanical technique for justifying the analytic de-Poissonization procedures involved. The methodology we develop can be easily adapted to many other problems with an underlying binomial distribution. In particular, the less expected and somewhat surprising n (logn)(2)-variance for certain notions of total path-length is also clarified.

scholarly journals Random Records and Cuttings in Split Trees: Extended Abstract

2008 ◽  
Vol DMTCS Proceedings vol. AI,... (Proceedings) ◽  
Author(s):  
Cecilia Holmgren
Keyword(s):  
Search Tree ◽  
Binary Search ◽  
Binary Search Tree ◽  
Search Trees ◽  
Digital Search Trees ◽  
International Audience ◽  
Split Trees ◽  
Digital Search

International audience We study the number of records in random split trees on $n$ randomly labelled vertices. Equivalently the number of random cuttings required to eliminate an arbitrary random split tree can be studied. After normalization the distributions are shown to be asymptotically $1$-stable. This work is a generalization of our earlier results for the random binary search tree which is one specific case of split trees. Other important examples of split trees include $m$-ary search trees, quadtrees, median of $(2k+1)$-trees, simplex trees, tries and digital search trees.

scholarly journals Approximate Counting via the Poisson-Laplace-Mellin Method

2012 ◽  
Vol DMTCS Proceedings vol. AQ,... (Proceedings) ◽  
Author(s):  
Michael Fuchs ◽  
Chung-Kuei Lee ◽  
Helmut Prodinger
Keyword(s):  
Error Tolerance ◽  
Approximate Counting ◽  
Shape Parameters ◽  
Search Trees ◽  
Huge Number ◽  
Digital Search Trees ◽  
International Audience ◽  
Compact Expression ◽  
The One ◽  
Digital Search

International audience Approximate counting is an algorithm that provides a count of a huge number of objects within an error tolerance. The first detailed analysis of this algorithm was given by Flajolet. In this paper, we propose a new analysis via the Poisson-Laplace-Mellin approach, a method devised for analyzing shape parameters of digital search trees in a recent paper of Hwang et al. Our approach yields a different and more compact expression for the periodic function from the asymptotic expansion of the variance. We show directly that our expression coincides with the one obtained by Flajolet. Moreover, we apply our method to variations of approximate counting, too.

scholarly journals Distributional asymptotics in the analysis of algorithms: Periodicities and discretization

2007 ◽  
Vol DMTCS Proceedings vol. AH,... (Proceedings) ◽  
Author(s):  
Rudolf Grübel
Keyword(s):  
Analysis Of Algorithms ◽  
Success Probability ◽  
Search Trees ◽  
Selection Algorithm ◽  
Background Process ◽  
Limit Distributions ◽  
Digital Search Trees ◽  
Tail Behaviour ◽  
International Audience ◽  
Digital Search

International audience It is well known that many distributions that arise in the analysis of algorithms have an asymptotically fluctuating behaviour in the sense that we do not have 'full' convergence, but only convergence along suitable subsequences as the size of the input to the algorithm tends to infinity. We are interested in constructions that display such behaviour via an ordinarily convergent background process in the sense that the periodicities arise from this process by deterministic transformations, typically involving discretization as a decisive step. This leads to structural representations of the resulting family of limit distributions along subsequences, which in turn may give access to their properties, such as the tail behaviour (unsuccessful search in digital search trees) or the dependence on parameters of the algorithm (success probability in a selection algorithm).

scholarly journals A weakly 1-stable distribution for the number of random records and cuttings in split trees

2011 ◽  
Vol 43 (01) ◽  
pp. 151-177 ◽  
Author(s):  
Cecilia Holmgren
Keyword(s):  
Classical Limit ◽  
Stable Distribution ◽  
Search Tree ◽  
Binary Search ◽  
Binary Search Tree ◽  
Search Trees ◽  
Infinitely Divisible ◽  
Digital Search Trees ◽  
Split Trees ◽  
Digital Search

In this paper we study the number of random records in an arbitrary split tree (or, equivalently, the number of random cuttings required to eliminate the tree). We show that a classical limit theorem for the convergence of sums of triangular arrays to infinitely divisible distributions can be used to determine the distribution of this number. After normalization the distributions are shown to be asymptotically weakly 1-stable. This work is a generalization of our earlier results for the random binary search tree in Holmgren (2010), which is one specific case of split trees. Other important examples of split trees includem-ary search trees, quad trees, medians of (2k+ 1)-trees, simplex trees, tries, and digital search trees.

scholarly journals Digital Search Trees Again Revisited: The Internal Path Length Perspective

1994 ◽  
Vol 23 (3) ◽  
pp. 598-616 ◽  
Author(s):  
Peter Kirschenhofer ◽  
Helmut Prodinger ◽  
Wojciech Szpankowski
Keyword(s):  
Path Length ◽  
Search Trees ◽  
Digital Search Trees ◽  
Digital Search
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