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Faster treasure hunt and better strongly universal exploration sequences

18th International Symposium on algorithms and Computations (ISAAC 2007)

作者： Xin, Qin Univ Bergen Dept Informat N-5008 Bergen Norway

ISBN: (纸本)9783540771180

We study the explicit deterministic treasure hunt problem in an n-vertex network. This problem was firstly introduced by Ta-Shma, and Zwick in [9] [SODA'07]. It is the variant of the well known rendezvous problem in which one of the robot (the treasure) is always stationary. We obtain an O(n(c (1+1/lambda)))-time solution for this problem, which significantly improves the currently best known result of running time O(n(2c)) in [9], where c is a fixed constant from the construction of an universal exploration sequence in [8,9], lambda is a constant integer and lambda >> 1. The treasure hunt problem motivates the study of strongly universal exploration sequences. We give a better explicit construction of strongly universal exploration sequences than the one in [9].

关键词： design and analysis of algorithms distributed computing networks rendezvous strongly universal exploration sequences

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Repetitive Processes and Their Surrogate-Model Congruent Encoding for Evolutionary algorithms - A Theoretic Proposal

Repetitive Processes and Their Surrogate-Model Congruent Enc...

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Genetic and Evolutionary Computation Conference (GECCO)

作者： Plump, Christina Berger, Bernhard J. Drechsler, Rolf DFKI Cyber Phys Syst Bremen Germany Hamburg Univ Technol Inst Embedded Syst Hamburg Germany Univ Bremen Dept Math Bremen Germany Univ Bremen Dept Comp Sci Bremen Germany

ISBN: (纸本)9798400701207

Evolutionary algorithms are a well-known optimisation technique. They can handle very different optimisation tasks and deal with distorted search spaces as well as non-differentiable optimisation functions. One crucial aspect in the design of evolutionary algorithms is the choice of encoding. Especially its interplay with the other components of the evolutionary algorithm is a relevant factor for the success of an evolutionary algorithm. While some encoding situations are relatively trivial, others pose a challenge. We focus on encoding repetitive processes, i.e. processes that consist of several variations of the same basic process (only with varied parameters). Our work proposes a possible technique that enables the validity of the encoded search space. We also provide adaptions to the standard operators of evolutionary algorithms to ensure they produce valid solutions. Furthermore, we show how this encoding technique is compatible with using a surrogate function for the fitness calculation and may reduce the necessary training data.

关键词： evolutionary algorithm design and analysis of algorithms surrogate model theory and algorithms for application

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Revealing the Inner Dynamics of Evolutionary algorithms with Convection Selection

Revealing the Inner Dynamics of Evolutionary Algorithms with...

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Genetic and Evolutionary Computation Conference (GECCO)

作者： Komosinski, Maciej Miazga, Konrad Poznan Univ Tech Inst Comp Sci Poznan Poland

ISBN: (纸本)9798400701207

Evolutionary algorithms are stochastic algorithms so they tend to find different solutions when run repeatedly. However, it is not just the solutions that vary - the very dynamics of the search that led to finding these solutions are likely to differ as well. It is especially in the algorithms with complex population structures - such as convection selection where a population is divided into subpopulations according to fitness values - where an opportunity for highly diverse dynamics arises. This work investigates the way evolutionary dynamics of subpopulations influence the performance of evolutionary algorithms with convection selection. We employ a demanding task of evolutionary design of 3D structures to analyze the relation between the properties of the optimization task and the features of the evolutionary process. Based on this analysis, we identify the mechanisms that influence the performance of convection selection, and suggest ways to improve this selection scheme.

关键词： evolutionary algorithms evolutionary dynamics design and analysis of algorithms convection selection

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Faster algorithms for string matching with k mismatches

Faster algorithms for string matching with <i>k</i> mismatch...

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11th Annual ACM/SIAM Symposium on Discrete algorithms

作者： Amir, A Lewenstein, M Porat, E Bar Ilan Univ Dept Math & Comp Sci IL-52900 Ramat Gan Israel Georgia Inst Technol Coll Comp Atlanta GA 30332 USA

ISBN: (纸本)0898714532

The string matching with mismatches problem is that of finding the number of mismatches between a pattern P of length in and every length in substring of the text T. Currently, the fastest algorithms for this problem are the following. The Galil-Giancarlo algorithm finds all locations where the pattern has at most k errors (where k is part of the input) in time O (nk). The Abrahamson algorithm finds the number of mismatches at every location in time O (nrootm log m). We present an algorithm that is faster than both. Our algorithm finds all locations where the pattern has at most k errors in time O(nrootk log k). We also show an algorithm that solves the above problem in time O ((n + (nk(3))/m) log k). (C) 2003 Elsevier Inc. All rights reserved.

关键词： design and analysis of algorithms combinatorial algorithms on words approximate string matching Hamming distance

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Finding Mobile Data under Delay Constraints with Searching Costs

Finding Mobile Data under Delay Constraints with Searching C...

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29th ACM SIGACT-SIGOPS Symposium on Principles of Distributed Computing

作者： Bar-Noy, Amotz Cheilaris, Panagiotis Feng, Vi Levin, Asaf CUNY Grad Ctr New York NY 10016 USA

ISBN: (纸本)9781605588889

A token is hidden in one of several boxes and then the boxes are locked. The probability of placing the token in each of the boxes is known. A searcher is looking for the token by unlocking boxes where each box is associated with an unlocking cost. The searcher conducts its search in rounds and must find the token in a predetermined number of rounds. In each round, the searcher may unlock any set of locked boxes concurrently. The optimization goal is to minimize the expected cost of unlocking boxes until the token is found. The motivation and main application of this game is the task of paging a mobile user (token) who is roaming in a zone of cells (boxes) in a cellular network system. Here, the unlocking costs reflect cell congestions and the placing probabilities represent the likelihood of the user residing in particular cells. Another application is the task of finding some data (token) that may be known to one of the sensors (boxes) of a sensor network. Here, the unlocking costs reflect the energy consumption of querying sensors and the placing probabilities represent the likelihood of the data being found in particular sensors. In general, we call mobile data any entity that has to be searched for. The special case, in which all the boxes have equal unlocking costs has been well studied in recent years and several optimal polynomial time solutions exist. To the best of our knowledge, this paper is the first to study the general problem in which each box may be associated with a different unlocking cost. We first present three special interesting and important cases for which optimal polynomial time algorithms exist: (i) There is no a priori knowledge about the location of the token and therefore all the placing probabilities are the same. (ii) There are no delay constraints so in each round only one box is unlocked. (iii) The token is atypical in the sense that it is more likely to be placed in boxes whose unlocking cost is low. Next, we consider the case of a

关键词： Partitioning and scheduling design and analysis of algorithms approximation algorithms

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Efficient text fingerprinting via parikh mapping

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Journal of Discrete algorithms 2003年第5-6期1卷 409-421页

作者： Amir, Amihood Apostolico, Alberto Landau, Gad M. Satta, Giorgio Department of Mathematics and Computer Science Bar-Ilan University 52900 Ramat-Gan Israel Dipartimento di Elettronica e Informatica Università di Padova 35131 Padova Via Gradenigo 6/A Italy Department of Computer Sciences Purdue University Computer Sciences Building West Lafayette IN 47907 United States Department of Computer Science Haifa University Haifa 31905 Israel Department of Computer and Information Science Polytechnic University Six MetroTech Center Brooklyn NY 11201-3840 United States College of Computing Georgia Institute of Technology Atlanta GA 30332-0280 United States

We consider the problem of fingerprinting text by sets of symbols. Specifically, if S is a string, of length n, over a finite, ordered alphabet Σ, and S' is a substring of S, then the fingerprint of S' is the subset φ of Σ of precisely the symbols appearing in S'. In this paper we show efficient methods of answering various queries on fingerprint statistics. Our preprocessing is done in time O(n |Σ| log n log |Σ|) and enables answering the following queries: (1) Given an integer k, compute the number of distinct fingerprints of size k in time O(1). (2) Given a set φ ⊆ Σ, compute the total number of distinct occurrences in S of substrings with fingerprint φ in time O(| Σ| log n). © 2003 Elsevier B.V. All rights reserved.

关键词： Combinatorial algorithms on words design and analysis of algorithms

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Efficient enumeration of phylogenetically informative substrings

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10th Annual International Conference on Research in Computational Molecular Biology

作者： Angelov, Stanislav Harb, Boulos Kannan, Sampath Khanna, Sanjeev Kim, Junhyong Univ Penn Dept Comp & Informat Sci Philadelphia PA 19104 USA Univ Penn Dept Biol Philadelphia PA 19104 USA

ISBN: (纸本)3540332952

We study the problem of enumerating substrings that are common amongst genomes that share evolutionary descent. For example, one might want to enumerate all identical (therefore conserved) substrings that are shared between all mammals and not found in nonmammals. Such collection of substrings may be used to identify conserved subsequences or to construct sets of identifying substrings for branches of a phylogmetic tree. For two disjoint sets of genomes on a phylogenetic tree, a substring is called a tag if it is found in all of the genomes of one set and none of the genomes of the other set. We present a near-linear time algorithm that finds all tags in a given phylogeny;and a sublinear space algorithm (at the expense of running time) that is more suited for very large data sets. Under a stochastic model of evolution, we show that a simple process of tag-generation essentially captures all possible ways of generating tags. We use this insight to develop a faster tag discovery algorithm with a small chance of error. However, since tags are not guaranteed to exist in a given data set, we generalize the notion of a tag from a single substring to a set of substrings. We present a linear programming-based approach for finding approximate generalized tag sets. Finally, we use our tag enumeration algorithm to analyze a phylogeny containing 57 whole microbial genomes. We find tags for all nodes in the phylogeny except the root for which we find generalized tag sets.

关键词： design and analysis of algorithms phylogenetically informative substring phylogeny stochastic analysis suffix tree

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A Time-Randomness Tradeoff for Quasi-Random Rumour Spreading

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Electronic Notes in Discrete Mathematics 2009年 34卷 335-339页

作者： Doerr, Benjamin Fouz, Mahmoud Max-Planck-Institut für Informatik D-66123 Saarbrücken Germany Universität des Saarlandes D-66123 Saarbrücken Germany

We give a time-randomness tradeoff for the quasi-random rumour spreading protocol proposed by Doerr et al [Doerr, B., T. Friedrich, and T. Sauerwald. Quasirandom rumor spreading. In Proc. of the 19th Annual ACM-SIAM Symp. on Disc. Alg., pages 773-781, 2008] on complete graphs. In this protocol, the goal is to spread a piece of information originating from one vertex throughout the network. Each vertex is assumed to have a (cyclic) list of its neighbors. Once a vertex is informed by one of its neighbors, it chooses a position in its list uniformly at random and goes on to inform its neighbors starting from that position and proceeding in order of the list. Doerr et al [Doerr, B., T. Friedrich, and T. Sauerwald. Quasirandom rumor spreading. In Proc. of the 19th Annual ACM-SIAM Symp. on Disc. Alg., pages 773-781, 2008.] showed that after O(log n) rounds, the rumour will have been broadcasted to all nodes with probability 1 - o (1). We study the broadcast time when the amount of randomness available at each node is reduced. For randomness parameter ℓ, we show that there exists lists such that (1 - ε) (log₂ n + ln n - log₂ ℓ - ln ℓ) + ℓ steps are needed to inform every vertex with probability at least 1 - O (e^{- frac(nε, 2 ln n)}). © 2009 Elsevier B.V. All rights reserved.

关键词： design and analysis of algorithms Randomness in Computation

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Faster two-dimensional pattern matching with rotations

Faster two-dimensional pattern matching with rotations

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15th Annual Symposium on Combinatorial Pattern Matching

作者： Amir, Amihood Kapah, Oren Tsur, Dekel Bar Ilan Univ Dept Comp Sci IL-52900 Ramat Gan Israel Bar Ilan Univ Dept Comp Sci IL-52900 Ramat Gan Israel Ben Gurion Univ Negev Dept Comp Sci IL-84105 Beer Sheva Israel

ISBN: (纸本)354022341X

The most efficient currently known algorithms for two-dimensional pattern matching with rotations have a worst case time complexity of O(n(2)m(3)), where the size of the text is n x n and the size of the pattern is m x m. In this paper we present a new algorithm for the problem whose running time is 0(n(2),m(2)). (c) 2006 Published by Elsevier B.V.

关键词： design and analysis of algorithms two-dimensional pattern matching rotation

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Improved Lion Optimization Algorithm for Wavelet Threshold Method in Ground-Borehole Transient Electromagnetic Signal Processing 24

Improved Lion Optimization Algorithm for Wavelet Threshold M...

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6th International Conference on Telecommunications and Communication Engineering

作者： Yang, Shuai Cao, Hui Song, Wenxu Chengdu Univ Technol Sch Mech & Elect Engn Chengdu Sichuan Peoples R China Chengdu Univ Technol Sch Geophys Chengdu Sichuan Peoples R China

ISBN: (纸本)9798400709630

This paper proposes a wavelet denoising algorithm based on an improved lion optimization threshold strategy. By introducing weight and adjustment factors into the standard lion optimization algorithm, the local and global optimization capabilities are enhanced. During the algorithm verification, forward modeling and theoretical signals generated with different noise were processed, showing that this algorithm significantly improved the signal-to-noise ratio and root mean square error of the signals. When applied to measured transient electromagnetic signals after data preprocessing, the inversion accuracy was further improved. The results demonstrate that this method can accurately separate useful signals from noise and improve signal quality, making it an effective signal denoising method.

关键词： CCS CONCEPTS Theory of computation design and analysis of algorithms Mathematical optimization Discrete optimization Network optimization Additional Keywords and Phrases: Lion optimization Wavelet denoising algorithm Threshold strategy Data preprocessing

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