Results 1  10
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45
IDMaps: A Global Internet Host Distance Estimation Service
 In Proceedings of IEEE INFOCOM
, 2000
"... There is an increasing need to quickly and efficiently learn network distances, in terms of metrics such as latency or bandwidth, between Internet hosts. For example, Internet content providers often place data and server mirrors throughout the Internet to improve access latency for clients, and it ..."
Abstract

Cited by 254 (13 self)
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There is an increasing need to quickly and efficiently learn network distances, in terms of metrics such as latency or bandwidth, between Internet hosts. For example, Internet content providers often place data and server mirrors throughout the Internet to improve access latency for clients, and it is necessary to direct clients to the closest mirrors based on some distance metric in order to realize the benefit of mirrors. We suggest a scalable Internetwide architecture, called IDMaps, which measures and disseminates distance information on the global Internet. Higherlevel services can collect such distance information to build a virtual distance map of the Internet and estimate the distance between any pair of IP addresses. We present our solutions to the measurement server placement and distance map construction problems in IDMaps. We show that IDMaps can indeed provide useful distance estimations to applications such as closestmirror selection. 1 Keywords: network service, distributed algorithms, scalability, modeling. 1
A Genetic Algorithm for the Set Covering Problem
 European Journal of Operational Research
, 1996
"... In this paper we present a genetic algorithmbased heuristic for nonunicost set covering problems. We propose several modifications to the basic genetic procedures including a new fitnessbased crossover operator (fusion), a variable mutation rate and a heuristic feasibility operator tailored speci ..."
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Cited by 128 (4 self)
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In this paper we present a genetic algorithmbased heuristic for nonunicost set covering problems. We propose several modifications to the basic genetic procedures including a new fitnessbased crossover operator (fusion), a variable mutation rate and a heuristic feasibility operator tailored specifically for the set covering problem. The performance of our algorithm was evaluated on a large set of randomly generated problems. Computational results showed that the genetic algorithmbased heuristic is capable of producing highquality solutions. Keywords: genetic algorithms; set covering; optimisation. 1 Introduction The set covering problem (SCP) is the problem of covering the rows of a mrow, n column, zeroone matrix (a ij ) by a subset of the columns at minimal cost. Defining x j = 1 if column j (with cost c j ? 0) is in the solution and x j = 0 otherwise, the SCP is Minimise n X j=1 c j x j (1) Subject to n X j=1 a ij x j 1, i = 1; : : : ; m (2) x j 2 f0; 1g, j = 1; ...
Choosing Replica Placement Heuristics for WideArea Systems
 In ICDCS ’04: Proceedings of the 24th International Conference on Distributed Computing Systems (ICDCS’04
, 2004
"... Data replication is used extensively in widearea distributed systems to achieve low dataaccess latency. A large number of heuristics have been proposed to perform replica placement. Practical experience indicates that the choice of heuristic makes a big difference in terms of the cost of required ..."
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Cited by 40 (0 self)
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Data replication is used extensively in widearea distributed systems to achieve low dataaccess latency. A large number of heuristics have been proposed to perform replica placement. Practical experience indicates that the choice of heuristic makes a big difference in terms of the cost of required infrastructure (e.g., storage capacity and network bandwidth), depending on system topology, workload and performance goals.
The Capacitated KCenter Problem
 In Proceedings of the 4th Annual European Symposium on Algorithms, Lecture Notes in Computer Science 1136
, 1996
"... The capacitated Kcenter problem is a fundamental facility location problem, where we are asked to locate K facilities in a graph, and to assign vertices to facilities, so as to minimize the maximum distance from a vertex to the facility to which it is assigned. Moreover, each facility may be assign ..."
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Cited by 34 (5 self)
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The capacitated Kcenter problem is a fundamental facility location problem, where we are asked to locate K facilities in a graph, and to assign vertices to facilities, so as to minimize the maximum distance from a vertex to the facility to which it is assigned. Moreover, each facility may be assigned at most L vertices. This problem is known to be NPhard. We give polynomial time approximation algorithms for two different versions of this problem that achieve approximation factors of 5 and 6. We also study some generalizations of this problem. 1. Introduction The basic Kcenter problem is a fundamental facility location problem [17] and is defined as follows: given an edgeweighted graph G = (V; E) find a subset S ` V of size at most K such that each vertex in V is "close" to some vertex in S. More formally, the objective function is defined as follows: min S`V max u2V min v2S d(u; v) where d is the distance function. For example, one may wish to install K fire stations and mi...
Geometric And Computational Aspects Of Manufacturing Processes
 Comput. & Graphics
, 1994
"... Two of the fundamental questions that arise in the manufacturing industry concerning every type of manufacturing process are: 1. Given an object, can it be built using a particular process? 2. Given that an object can be built using a particular process, what is the best way to construct the objec ..."
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Cited by 18 (7 self)
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Two of the fundamental questions that arise in the manufacturing industry concerning every type of manufacturing process are: 1. Given an object, can it be built using a particular process? 2. Given that an object can be built using a particular process, what is the best way to construct the object? The latter question gives rise to many different problems depending on how best is qualified. We address these problems for two complimentary categories of manufacturing processes: rapid prototyping systems and casting processes. The method we use to address these problems is to first define a geometric model of the process in question and then answer the questions on that model. In the category of rapid prototyping systems, we concentrate on stereolithography, which is emerging as one of the most popular rapid prototyping systems. We model stereolithography geometrically and then study the class of objects that admit a construction in this model. For the objects that admit a constructio...
ISAC  InstanceSpecific Algorithm Configuration
"... We present a new method for instancespecific algorithm configuration (ISAC). It is based on the integration of the algorithm configuration system GGA and the recently proposed stochastic offline programming paradigm. ISAC is provided a solver with categorical, ordinal, and/or continuous parameter ..."
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Cited by 16 (2 self)
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We present a new method for instancespecific algorithm configuration (ISAC). It is based on the integration of the algorithm configuration system GGA and the recently proposed stochastic offline programming paradigm. ISAC is provided a solver with categorical, ordinal, and/or continuous parameters, a training benchmark set of input instances for that solver, and an algorithm that computes a feature vector that characterizes any given instance. ISAC then provides high quality parameter settings for any new input instance. Experiments on a variety of different constrained optimization and constraint satisfaction solvers show that automatic algorithm configuration vastly outperforms manual tuning. Moreover, we show that instancespecific tuning frequently leads to significant speedups over instanceoblivious configurations.
Set covering approach for reconstruction of sibling relationships
 Optimization Methods and Software
, 2007
"... A new combinatorial approach for modelling and reconstructing sibling relationships in a single generation of individuals without parental information is proposed in this paper. Simple genetic constraints on the fullsibling groups, imposed by the Mendelian inheritance rules, are employed to investi ..."
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Cited by 15 (13 self)
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A new combinatorial approach for modelling and reconstructing sibling relationships in a single generation of individuals without parental information is proposed in this paper. Simple genetic constraints on the fullsibling groups, imposed by the Mendelian inheritance rules, are employed to investigate data from codominant DNA markers. To extract the minimum number of biologically consistent sibling groups, the proposed combinatorial approach is employed to formulate this minimization problem as a set covering problem, which is a wellknown NPhard combinatorial optimization problem. We conducted a simulation study of a relaxed version of the proposed algorithm to demonstrate that our combinatorial approach is reasonably accurate and the exact version of the sibling relationship construction algorithm should be pursued. In addition, the results of this study suggest that the proposed algorithm will pave our way to a new approach in computational population genetics as it does not require any a priori knowledge about allele frequency, population size, mating system or family size distributions to reconstruct sibling relationships.
GraphTheoretical Models for Frequency Assignment Problems
, 1997
"... In the present dissertation we investigate structural and algorithmic aspects of the frequency assignment problem in mobile telephone networks. This problem is of particular interest for the graph theory because of its close relationship to graph coloring. The frequency assignment problem includes t ..."
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Cited by 14 (0 self)
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In the present dissertation we investigate structural and algorithmic aspects of the frequency assignment problem in mobile telephone networks. This problem is of particular interest for the graph theory because of its close relationship to graph coloring. The frequency assignment problem includes the characteristic features of Tcoloring, list coloring, and set coloring, and belongs thereby to NPhard combinatorial problems. The main part of this thesis is dedicated to the socalled hybrid networks, with some stations operating according to the static principle and other stations according to the dynamic principle. We develop a graphtheoretical model and introduce two optimization criteria for the frequency assignment problem in hybrid networks. The computational complexity of evaluating these criteria is first examined for graphs with bounded treewidth and for complete graphs. In the further investigations we concentrate on the criterion called channel stability number, which genera...
Computing the Constrained Euclidean, Geodesic and Link Centre of a Simple Polygon with Applications
"... In the manufacturing industry, finding a suitable location for the pin gate (the pin gate is the point from which liquid is poured or injected into a mold) is a difficult problem when viewed from the fluid dynamics of the molding process. However, experience has shown that a suitable pin gate locati ..."
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Cited by 12 (5 self)
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In the manufacturing industry, finding a suitable location for the pin gate (the pin gate is the point from which liquid is poured or injected into a mold) is a difficult problem when viewed from the fluid dynamics of the molding process. However, experience has shown that a suitable pin gate location possesses several geometric characteristics, namely the distance from the pin gate to any point in the mold should be small and the number of turns on the path from a point in the mold to the pin gate should be small. We address the problem of computing locations that possess these geometric characteristics. Given a mold M (modeled by an n vertex simple polygon) we show how to compute the Euclidean center of M constrained to lie in the interior of M or on the boundary of M in O(n log n+k) time where k is the number of intersections between M and the furthest point Voronoi diagram of the vertices of M . We show how to compute the geodesic center of M constrained to the boundary in O(n log n) time and the geodesic center of M constrained to lie in a polygonal region in O(n(n + k)) time. Finally, we show how to compute the link center of M constrained to the boundary of M in O(n log n) time.
A Modeling Framework for Facility Location of Medical Services for LargeScale Emergencies
, 2005
"... Research on facility location is abundant. However, this research does not typically address the particular conditions that arise when locating facilities to service largescale emergencies, such as earthquakes, terrorist attacks, etc. In this work we first survey general facility location problem ..."
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Cited by 8 (2 self)
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Research on facility location is abundant. However, this research does not typically address the particular conditions that arise when locating facilities to service largescale emergencies, such as earthquakes, terrorist attacks, etc. In this work we first survey general facility location problems and identify models used to address common emergency situations, such as house fires and regular health care needs. We then analyze the characteristics of largescale emergencies and propose a general facility location model that is suited for largescale emergencies. This general facility location model can be cast as a covering model, a Pmedian model or a Pcenter model, each suited for different needs in a largescale emergency. Illustrative examples are given to show how the proposed model can be used to optimize the locations of facilities for medical supplies to address largescale emergencies in the Los Angeles area. Furthermore, comparison of the solutions obtained by respectively using the proposed model and the traditional model is given to show the benefits of the proposed model in reducing lifeloss and economic loss.