Springer Optimization and Its Applications
VOLUME 62
Managing Editor
Panos M. Pardalos (University of Florida)
Editor–Combinatorial Optimization
Ding-Zhu Du (University of Texas at Dallas)
Advisory Board
J. Birge (University of Chicago)
C.A. Floudas (Princeton University)
F. Giannessi (University of Pisa)
H.D. Sherali (Virginia Polytechnic and State University)
T. Terlaky (McMaster University)
Y. Ye (Stanford University)
Aims and Scope
Optimization has been expanding in all directions at an astonishing rate
during the last few decades. New algorithmic and theoretical techniques
have been developed, the diffusion into other disciplines has proceeded at
a rapid pace, and our knowledge of all aspects of the field has grown even
more profound. At the same time, one of the most striking trends in opti-
mization is the constantly increasing emphasis on the interdisciplinary na-
ture of the field. Optimization has been a basic tool in all areas of applied
mathematics, engineering, medicine, economics, and other sciences.
The series Springer Optimization and Its Applications publishes under-
graduate and graduate textbooks, monographs and state-of-the-art exposi-
tory work that focus on algorithms for solving optimization problems and
also study applications involving such problems. Some of the topics covered
include nonlinear optimization (convex and nonconvex), network flow prob-
lems, stochastic optimization, optimal control, discrete optimization, multi-
objective programming, description of software packages, approximation
techniques and heuristic approaches.
For further volumes:
http://www.springer.com/series/7393
Ding-Zhu Du •Ker-I KoDesign and Analysisof Approximation AlgorithmsXiaodong Hu•
Ding-Zhu Du Ker-I Ko Department of Computer Science Department of Computer Science University of Texas at Dallas State University of New York at Stony Brook Richardson, TX 75080 Stony Brook, NY 11794 USA USA dzdu@utdallas.edu keriko@cs.sunysb.edu Xiaodong Hu Institute of Applied Mathematics Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China xdhu@amss.ac.cn ISSN 1931-6828 ISBN 978-1-4614-1700-2 e-ISBN 978-1-4614-1701-9 DOI 10.1007/978-1-4614-1701-9 Springer New York Dordrecht Heidelberg London Library of Congress Control Number: Springer Science+Business Media, LLC 2012 All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer soft-ware, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. Printed on acid-free paper Springer is part of Springer Science+Business Media (www.springer.com) 2011942512
PrefaceAnapproximationalgorithmisanefficientalgorithmthatproducessolutionstoanoptimizationproblemthatareguaranteedtobewithinafixedratiooftheoptimalsolution.Insteadofspendinganexponentialamountoftimefindingtheoptimalsolution,anapproximationalgorithmsettlesfornear-optimalsolutionswithinpoly-nomialtimeintheinputsize.Approximationalgorithmshavebeenstudiedsincethemid-1960s.Theirimportancewas,however,notfullyunderstooduntilthediscov-eryoftheNP-completenesstheory.Manywell-knownoptimizationproblemshavebeenproved,underreasonableassumptionsinthistheory,tobeintractable,inthesensethatoptimalsolutionstotheseproblemsarenotcomputablewithinpolyno-mialtime.Asaconsequence,near-optimalapproximationalgorithmsarethebestonecanexpectwhentryingtosolvetheseproblems.Inthepastdecade,theareaofapproximationalgorithmshasexperiencedanex-plosiverateofgrowth.Thisgrowthrateispartlyduetothedevelopmentofrelatedresearchareas,suchasdatamining,communicationnetworks,bioinformatics,andcomputationalgametheory.Thesenewlyestablishedresearchareasgeneratealargenumberofnew,intractableoptimizationproblems,mostofwhichhavedirectappli-cationstoreal-worldproblems,andsoefficientapproximatesolutionstothemareactivelysoughtafter.Inadditiontotheexternal,practicalneedforefficientapproximationalgorithms,thereisalsoanintrinsic,theoreticalmotivebehindtheresearchofapproximationalgorithms.Inthedesignofanexact-solutionalgorithm,themain,andoftenonly,measureofthealgorithm’sperformanceisitsrunningtime.Thisfixedmeasureof-tenlimitsourchoiceoftechniquesinthealgorithm’sdesign.Foranapproximationalgorithm,however,thereisanequallyimportantsecondmeasure,thatis,theper-formanceratioofthealgorithm,whichmeasureshowclosetheapproximational-v
viPrefacegorithm’soutputistotheoptimalsolution.Thismeasureaddsanewdimensiontothedesignandanalysisofapproximationalgorithms.Namely,wecannowstudythetradeoffbetweentherunningtimeandtheperformanceratioofapproximationalgo-rithms,andapplydifferentdesigntechniquestoachievedifferenttradeoffsbetweenthesetwomeasures.Inaddition,newtheoreticalissuesabouttheapproximationtoanoptimizationproblemneedtobeaddressed:Whatistheperformanceratioofanapproximationalgorithmforthisproblembasedoncertaintypesofdesignstrategy?Whatisthebestperformanceratioofanypolynomial-timeapproximationalgorithmforthisproblem?Doestheproblemhaveapolynomial-timeapproximationschemeorafullypolynomial-timeapproximationscheme?Thesequestionsarenotonlyofsignificanceinpracticeforthedesignofapproximationalgorithms;theyarealsoofgreattheoreticalinterest,withintriguingconnectionstotheNP-completenessthe-ory.Motivatedbythesetheoreticalquestionsandthegreatnumberofnewlydiscov-eredoptimizationproblems,peoplehavedevelopedmanynewdesigntechniquesforapproximationalgorithms,includingthegreedystrategy,therestrictionmethod,therelaxationmethod,partition,localsearch,powergraphs,andlinearandsemidef-initeprogramming.Acomprehensivesurveyofallthesemethodsandresultsinasinglebookisnotpossible.Weinsteadprovideinthisbookanintensivestudyofthemainmethods,withabundantapplicationsfollowingourdiscussionofeachmethod.Indeed,thisbookisorganizedaccordingtodesignmethodsinsteadofapplicationproblems.Thus,onecanstudyapproximationalgorithmsofthesamenatureto-gether,andlearnaboutthedesigntechniquesinamoreunifiedway.Tothisend,thebookisarrangedinthefollowingway:First,inChapter1,wegiveabriefintroduc-tiontotheconceptofNP-completenessandapproximationalgorithms.InChapter2,wegiveanin-depthanalysisofthegreedystrategy,includinggreedyalgorithmswithsubmodularpotentialfunctionsandthosewithnonsubmodularpotentialfunc-tions.InChapters3,4,and5,wecovervariousrestrictionmethods,includingpar-titionandGuillotinecutmethods,withapplicationstomanygeometricproblems.Inthenextfourchapters,westudytherelaxationmethods.InadditiontoageneraldiscussionoftherelaxationmethodinChapter6,wedevotethreechapterstoap-proximationalgorithmsbasedonlinearandsemidefiniteprogramming,includingtheprimal-dualschemaanditsequivalencewiththelocalratiomethod.Finally,inChapter10,wepresentvariousinapproximabilityresultsbasedonrecentworkintheNP-completenesstheory.Anumberofexamplesandexercisesareprovidedforeachdesigntechnique.Theyaredrawnfromdiverseareasofresearch,includingcommunicationnetworkdesign,opticalnetworks,wirelessadhocnetworks,sensornetworks,bioinformatics,socialnetworks,industrialengineering,andinformationmanagementsystems.ThisbookhasgrownoutoflecturenotesusedbytheauthorsattheUniversityofMinnesota,UniversityofTexasatDallas,TsinghuaUniversity,GraduateSchoolofChineseAcademyofSciences,Xi’anJiaotongUniversity,ZhejiangUniversity,EastChinaNormalUniversity,DalianUniversityofTechnology,XinjiangUniver-sity,NankaiUniversity,LanzhouJiaotongUniversity,XidianUniversity,andHarbinInstituteofTechnology.Inatypicalone-semesterclassforfirst-yeargraduatestu-
Prefaceviidents,onemaycoverthefirsttwochapters,oneortwochaptersontherestrictionmethod,twoorthreechaptersontherelaxationmethod,andChapter10.Withmoreadvancedstudents,onemayalsoteachaseminarcoursefocusingononeofthegreedy,restriction,orrelaxationmethods,basedonthecorrespondingchaptersofthisbookandsupplementarymaterialfromrecentresearchpapers.Forinstance,aseminaroncombinatorialoptimizationemphasizingapproximationsbasedonlinearandsemidefiniteprogrammingcanbeorganizedusingChapters7,8,and9.Thisbookhasbenefitedmuchfromthehelpofourfriends,colleagues,andstu-dents.WeareindebtedtoPeng-JunWan,WeiliWu,XiuzhenCheng,JieWang,Yin-fengXu,ZhaoZhang,DeyingLi,HejiaoHuang,HongZhu,GuochuanZhang,WeiWang,ShugangGao,XiaofengGao,FengZou,LingDing,XianyueLi,MyT.Thai,DonghyunKim,J.K.Willson,andRoozbehEbrahimiSoorchaei,whomademuch-valuedsuggestionsandcorrectionstotheearlierdraftsofthebook.WearealsogratefultoProfessorsFrancesYao,RichardKarp,RonaldGraham,andFanChungfortheirencouragement.SpecialthanksareduetoProfessorAndrewYaoandtheInstituteforTheoreticalComputerScience,TsinghuaUniversity,forthegeneroussupportandstimulatingenvironmenttheyprovidedforthefirsttwoauthorsduringtheirnumerousvisitstoTsinghuaUniversity.Dallas,TexasDing-ZhuDuStonyBrook,NewYorkKer-IKoBeijing,ChinaXiaodongHuAugust2011