Approximation and Online Algorithms: 7th International Workshop,WAOA 2009, Copenhagen Denmark, September 10-11, 2009. Revised Papers

264 Pages·2010·3.11 MB·English

by  Spyros Angelopoulos (auth.)

Lecture Notes in Computer Science 5893
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CarnegieMellonUniversity,Pittsburgh,PA,USA
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UniversityofSurrey,Guildford,UK
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UniversityofCalifornia,Irvine,CA,USA
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IndianInstituteofTechnology,Madras,India
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MicrosoftResearch,Cambridge,MA,USA
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UniversityofCalifornia,LosAngeles,CA,USA
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UniversityofCalifornia,Berkeley,CA,USA
GerhardWeikum
Max-PlanckInstituteofComputerScience,Saarbruecken,Germany
Evripidis Bampis Klaus Jansen (Eds.)
Approximation and
Online Algorithms
7th International Workshop,WAOA 2009
Copenhagen, Denmark, September 10-11, 2009
Revised Papers
1 3
VolumeEditors
EvripidisBampis
Universitéd’EvryVald’Essonne,IBISC,CNRSFRE3190
PlacedesTerasses,TourEvry2,91000EvryCedex,France
E-mail:[email protected]
KlausJansen
UniversitätKiel,InstitutfürInformatik
Olshausenstr.40,24098Kiel,Germany
E-mail:[email protected]
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Preface
The 7th Workshop on Approximation and Online Algorithms (WAOA 2009)
focused on the design and analysis of algorithms for online and computation-
ally hardproblems. Bothkinds of problems have a largenumber of applications
from a variety of fields. WAOA 2009 took place in Copenhagen, Denmark, dur-
ing September 10–11, 2009. The workshop was part of the ALGO 2009 event
that also hosted ESA 2009, IWPEC 2009, and ATMOS 2009. The previous
WAOA workshops were held in Budapest (2003), Rome (2004), Palma de Mal-
lorca(2005),Zurich(2006),Eilat(2007),andKarlsruhe(2008).Theproceedings
ofthesepreviousWAOAworkshopshaveappearedasLNCSvolumes2909,3351,
3879, 4368,4927, and 5426,respectively.
Topics of interest for WAOA 2009 were: algorithmic game theory, approx-
imation classes, coloring and partitioning, competitive analysis, computational
finance, cuts and connectivity, geometric problems, inapproximability results,
mechanism design, network design, packing and covering, paradigms for design
andanalysisofapproximationandonlinealgorithms,parameterizedcomplexity,
randomization techniques, real-world applications, and scheduling problems.
In response to the call for papers, we received 62 submissions. Each submis-
sionwasreviewedbyatleastthreereferees,andthevastmajoritybyatleastfour
referees. The submissions were mainly judged on originality, technical quality,
andrelevancetothetopicsoftheconference.Basedonthereviews,theProgram
Committee selected 22 papers.
We are grateful to Andrei Voronkov for providing the EasyChair conference
system,whichwasusedtomanagetheelectronicsubmissions,thereviewprocess,
and the electronic PC meeting. It made our task much easier. We would also
like to thank all the authors who submitted papers to WAOA 2009 as well as
the local organizers of ALGO 2009.
December 2009 Evripidis Bampis
Klaus Jansen
Organization
Program Co-chairs
Evripidis Bampis University of Evry, France
Klaus Jansen University of Kiel, Germany
Program Committee
Vincenzo Auletta University of Salerno, Italy
Evripidis Bampis University of Evry, France
Nikhil Bansal IBM T.J. Research Center Watson, USA
Constantinos Daskalakis Microsoft Research and MIT, USA
Christoph Durr CNRS, Ecole Polytechnique, France
Friedrich Eisenbrand EPFL Lausanne, Switzerland
Thomas Erlebach University of Leicester, UK
Klaus Jansen University of Kiel, Germany
Christos Kaklamanis University of Patras,Greece
Sanjeev Khanna University of Pennsylvania, USA
Monaldo Mastrolilli IDSIA Lugano, Switzerland
Yuval Rabani Technion Haifa, Israel
Nicolas Schabanel CNRS, University Paris Diderot, France
Roberto Solis-Oba University of Western Ontario, Canada
Neal Young University of California Riverside, USA
Guochuan Zhang Zhejiang University Hangzhou, China
Referees
Susanne Albers Hiroshi Fujiwara
Eric Angel Stefan Funke
Elliot Anshelevich Mira Gonen
Yossi Azar laurent gourv`es
Marin Bougeret Fabrizio Grandoni
Andreas Brandsta¨dt Danny Hermelin
Jaros(cid:2)law Byrka Tobias Jacobs
Ioannis Caragiannis Panagiotis Kanellopoulos
Lin Chen Jochen Ko¨nemann
Marek Chrobak Elias Koutsoupias
Michael Elkin So¨ren Laue
Diodato Ferraioli Van Bang Le
Dimitris Fotakis Daniel Lokshtanov
Pierre Fraigniaud Bin Lu
VIII Organization
Shuang Luan Eric Remila
Pa´ll Melsted Thomas Rothvoss
Julian Mestre Heiko R¨oglin
Ioannis Milis Laura Sanita`
J´erˆome monnot Ulrich M. Schwarz
Hannes Moser Danny Segev
Nikolaus Mutsanas Bruce Shepherd
Tim Nonner Gregory Valiant
Christina Otte Carmine Ventre
Konstantinos Panagiotou Andreas Wiese
Evi Papaioannou Prudence W.H. Wong
Fanny Pascual Haifeng Xu
Ulrich Pferschy Deshi Ye
Lars Pra¨del Vassilis Zissimopoulos
Do¨m¨oto¨r Pa´lvo¨lgyi
Table of Contents
WAOA 2009
On the Competitiveness of the Online Asymmetric and Euclidean
Steiner Tree Problems ............................................ 1
Spyros Angelopoulos
Extension of the Nemhauser and Trotter Theorem to Generalized
Vertex Cover with Applications.................................... 13
Reuven Bar-Yehuda, Danny Hermelin, and Dror Rawitz
Price Fluctuations: To Buy or to Rent.............................. 25
Marcin Bienkowski
Approximation Algorithms for Multiple Strip Packing ................ 37
Marin Bougeret, Pierre Francois Dutot, Klaus Jansen,
Christina Otte, and Denis Trystram
Approximating Frequent Items in Asynchronous Data Stream over a
Sliding Window.................................................. 49
Ho-Leung Chan, Tak-Wah Lam, Lap-Kei Lee, and Hing-Fung Ting
Longest Wait First for Broadcast Scheduling (Extended Abstract)...... 62
Chandra Chekuri, Sungjin Im, and Benjamin Moseley
The Routing Open Shop Problem: New Approximation Algorithms..... 75
Ilya Chernykh, Nikita Dryuck, Alexander Kononov, and
Sergey Sevastyanov
On the Price of Stability for Undirected Network Design .............. 86
George Christodoulou, Christine Chung, Katrina Ligett,
Evangelia Pyrga, and Rob van Stee
Finding Dense Subgraphs in G(n,1/2).............................. 98
Atish Das Sarma, Amit Deshpande, and Ravi Kannan
ParameterizedAnalysis of Paging and List Update Algorithms......... 104
Reza Dorrigiv, Martin R. Ehmsen, and Alejandro Lo´pez-Ortiz
Online Scheduling of Bounded Length Jobs to Maximize Throughput... 116
Christoph Du¨rr, L(cid:2)ukasz Jez˙, and Kim Thang Nguyen
On the Additive Constant of the k-Server Work Function Algorithm.... 128
Yuval Emek, Pierre Fraigniaud, Amos Korman, and Adi Ros´en
X Table of Contents
A (4+(cid:2))-Approximation for the Minimum-Weight Dominating Set
Problem in Unit Disk Graphs...................................... 135
Thomas Erlebach and Matu´ˇs Mihala´k
Guard Games on Graphs: Keep the Intruder Out!.................... 147
Fedor V. Fomin, Petr A. Golovach, and Daniel Lokshtanov
Between a Rock and a Hard Place: The Two-to-One Assignment
Problem ........................................................ 159
Dries Goossens, Sergey Polyakovskiy, Frits C.R. Spieksma, and
Gerhard J. Woeginger
Scheduling and Packing Malleable Tasks with Precedence Constraints
of Bounded Width ............................................... 170
Elisabeth Gu¨nther, Felix G. Ko¨nig, and Nicole Megow
Online Minimization Knapsack Problem ............................ 182
Xin Han and Kazuhisa Makino
Optimization Problems in Multiple Subtree Graphs .................. 194
Danny Hermelin and Dror Rawitz
Multi-Criteria TSP: Min and Max Combined ........................ 205
Bodo Manthey
Packet Routing: Complexity and Algorithms ........................ 217
Britta Peis, Martin Skutella, and Andreas Wiese
Minimal Cost Reconfiguration of Data Placement in Storage Area
Network ........................................................ 229
Hadas Shachnai, Gal Tamir, and Tami Tamir
Competitive Multi-dimensional Dynamic Bin Packing via L-Shape Bin
Packing......................................................... 242
Prudence W.H. Wong and Fencol C.C. Yung
Author Index.................................................. 255
On the Competitiveness of the Online
Asymmetric and Euclidean Steiner Tree
Problems
Spyros Angelopoulos
Max-Planck-Institut fu¨r Informatik
Saarbru¨cken 66123, Germany
Abstract. Thispaperaddressesthecompetitivenessofonlinealgorithms
fortwoSteinerTreeproblems.Inthefirstproblem,theunderlyinggraph
isdirectedandhasboundedasymmetry,namelythemaximumweightof
antiparallel links in the graph does not exceed a parameter α. Previous
work onthisproblem hasleft agap on thecompetitiveratio whichisas
largeaslogarithmicink.Wepresentarefinedanalysis,bothintermsof
the upper and the lower bounds, that closes the gap and shows that a
greedy algorithm is optimal for all valuesof theparameter α.
The second part of the paper addresses the Euclidean Steiner tree
problem on the plane. Alon and Azar [SoCG 1992, Disc. Comp. Geom.
1993]gaveanelegantlowerboundonthecompetitiveratioofanydeter-
ministic algorithm equal to Ω(logk/loglogk); however, thebest known
upperboundisthetrivialboundO(logk).Wegivethefirstanalysisthat
makesprogress towardsclosingthislong-standinggap.Inparticular,we
present an online algorithm with competitive ratio O(logk/loglogk),
provided that the optimal offline Steiner tree belongs in a class of trees
with relatively simple structure. This class comprises not only the ad-
versarialinstancesofAlonandAzar,butalsoallrectilinearSteinertrees
whichcanbedecomposedinapolylogarithmicnumberofrectilinearfull
Steiner trees.
1 Introduction
Problem statements and motivation The Steiner treeproblemoccupiesacentral
place in combinatorial optimization, and has been studied extensively under
many variants. The standard setting involves an underlying graph G = (V,E),
with a non-negative weight function c : E → R+ over its edges (which reflects
thecostoftheedge).GivenasubsetK ⊆V ofverticesalsocalledterminals,the
objective is to find a tree of minimum cost that spans all vertices in K. Here,
the cost of the tree is defined as the sum of the cost of all the edges in the tree.
In this paper we focus on the following Steiner tree problems.
• IntheasymmetricSteinertreeproblem,theunderlyinggraphisdirected,and
a specific vertex r ∈ V is designated as the root. We define the asymmetry α
of graph G as the maximum ratio of the cost of antiparallel links in G. More
E.BampisandK.Jansen(Eds.):WAOA2009,LNCS5893,pp.1–12,2010.
(cid:2)c Springer-VerlagBerlinHeidelberg2010