Efficient parallel solutions have been found to many problems. Some of them can be obtained automatically from sequential programs, using compilers. However, there is a large class of problems - irregular problems - that lack efficient solutions. IRREGULAR 94 - a workshop and summer school organized in Geneva - addressed the problems associated with the derivation of efficient solutions to irregular problems. This book, which is based on the workshop, draws on the contributions of outstanding scientists to present the state of the art in irregular problems, covering aspects ranging from scientific computing, discrete optimization, and automatic extraction of parallelism. Audience: This first book on parallel algorithms for irregular problems is of interest to advanced graduate students and researchers in parallel computer science.

This volume contains the papers presented at the 12th International Wo- shop on Approximation Algorithms for Combinatorial Optimization Problems (APPROX 2009) and the 13th International Workshop on Randomization and Computation (RANDOM 2009), which took place concurrently at the HP - ditorium in UC Berkeley, USA, during August 21-23, 2009. APPROX focuses on algorithmic and complexity issues surrounding the development of e?cient approximate solutions to computationally di?cult problems, and was the 12th in the series after Aalborg (1998), Berkeley (1999), Saarbru ]cken (2000), Ber- ley (2001), Rome (2002), Princeton (2003), Cambridge (2004), Berkeley (2005), Barcelona (2006), Princeton (2007), and Boston (2008). RANDOM is concerned with applications of randomness to computational and combinatorial problems, and was the 13th workshop in the series following Bologna (1997), Barcelona (1998), Berkeley(1999), Geneva(2000), Berkeley(2001), Harvard(2002), Prin- ton (2003), Cambridge (2004), Berkeley (2005), Barcelona (2006), Princeton (2007), and Boston (2008). Topics of interest for APPROX and RANDOM are: design and analysis of approximation algorithms, hardness of approximation, small space algorithms, sub-linear time algorithms, streaming algorithms, embeddings and metric space methods, mathematicalprogrammingmethods, combinatorialproblemsingraphs andnetworks, gametheory, markets, andeconomicapplications, geometricpr- lems, packing, covering, scheduling, approximate learning, design and analysis of online algorithms, randomized complexity theory, pseudorandomness and - randomization, randomcombinatorialstructures, randomwalks/Markovchains, expander graphs and randomness extractors, probabilistic proof systems, err- correctingcodes, average-caseanalysis, propertytesting, computationallearning theory, and other applications of approximation and randomness. The volume contains 25 contributed papers, selected by the APPROX Program Committee out of 56 submissions, and 28 contributed papers, selected by the RANDOM Program Committee out of 57

This volume contains the papers presented at the 11th International Wo- shop on Approximation Algorithms for Combinatorial Optimization Problems (APPROX 2008) and the 12th International Workshop on Randomization and Computation (RANDOM 2008), which took place concurrently at the MIT (M- sachusetts Institute of Technology) in Boston, USA, during August 25-27, 2008. APPROX focuses on algorithmic and complexity issues surrounding the development of e?cient approximate solutions to computationally di?cult problems, and was the 11th in the series after Aalborg (1998), Berkeley (1999), Saarbru ]cken (2000), Berkeley (2001), Rome (2002), Princeton (2003), Cambridge (2004), Berkeley (2005), Barcelona (2006), and Princeton (2007). RANDOM is concerned with applications of randomness to computational and combinatorial problems, and was the 12th workshop in the series following Bologna (1997), Barcelona (1998), Berkeley (1999), Geneva (2000), Berkeley (2001), Harvard (2002), Princeton (2003), Cambridge (2004), Berkeley (2005), Barcelona (2006), and Princeton (2007). Topics of interest for APPROX and RANDOM are: design and analysis of - proximation algorithms, hardness of approximation, small space, sub-linear time, streaming, algorithms, embeddings and metric space methods, mathematical programming methods, combinatorial problems in graphs and networks, game t- ory, markets, economic applications, geometric problems, packing, covering, scheduling, approximate learning, design and analysis of randomized algorithms, randomized complexity theory, pseudorandomness and derandomization, random combinatorial structures, random walks/Markov chains, expander graphs and randomness extractors, probabilistic proof systems, random projections and - beddings, error-correcting codes, average-case analysis, property testing, com- tational learning theory, and other applications of approximation and randomness."

This volume contains the contributed papers and invited talks presented at the 1stInternationalWorkshoponAlgorithmicAspectsofWirelessSensorNetworks (ALGOSENSORS 2004), which was held July 16, 2004, in Turku, Finland, - located with the 31st International Colloquium on Automata, Languages, and Programming (ICALP 2004). Wireless ad hoc sensor networks have become a very important research subject due to their potential to provide diverse services in numerous appli- tions. The realization of sensor networks requires intensive technical research and development e?orts, especially in power-aware scalable wireless ad hoc c- munications protocols, due to their unusual application requirements and severe constraints. On the other hand, a solid theoretical background seems necessary for sensor networks to achieve their full potential. It is an algorithmic challenge to achieve e?cient and robust realizations of such large, highly dynamic, complex, n- conventional networking environments. Features, including the huge number of sensor devices involved, the severe power, computational and memory limi- tions, their dense deployment and frequent failures, pose new design, analysis and implementation challenges. This event is intended to provide a forum for researchers and practitioners to present their contributions related to all aspects of wireless sensor networks. Topics of interest for ALGOSENSORS 2004 were: - Modeling of speci?c sensor networks. - Methods for ad hoc deployment. - Algorithms for sensor localization and tracking of mobile users. - Dynamic sensor networks. - Hierarchical clustering architectures. - Attribute-based named networks. - Routing: implosion issues and resource management. - Communication protocols. - Media access control in sensor networks. - Simulators for sensor networks.

The technique of randomization has been employed to solve numerous prob lems of computing both sequentially and in parallel. Examples of randomized algorithms that are asymptotically better than their deterministic counterparts in solving various fundamental problems abound. Randomized algorithms have the advantages of simplicity and better performance both in theory and often is a collection of articles written by renowned experts in practice. This book in the area of randomized parallel computing. A brief introduction to randomized algorithms In the analysis of algorithms, at least three different measures of performance can be used: the best case, the worst case, and the average case. Often, the average case run time of an algorithm is much smaller than the worst case. 2 For instance, the worst case run time of Hoare's quicksort is O(n ), whereas its average case run time is only O(nlogn). The average case analysis is conducted with an assumption on the input space. The assumption made to arrive at the O(n logn) average run time for quicksort is that each input permutation is equally likely. Clearly, any average case analysis is only as good as how valid the assumption made on the input space is. Randomized algorithms achieve superior performances without making any assumptions on the inputs by making coin flips within the algorithm. Any analysis done of randomized algorithms will be valid for all possible inputs.

TheWorkshoponRandomizationandApproximationTechniquesinComputer Science, Random'98, focuses on algorithmic and complexity aspects arising inthedevelopmentofe cientrandomizedsolutionstocomputationallydi cult problems. Itaims,inparticular,atfosteringthecooperationamongpractitioners andtheoreticiansandamongalgorithmicandcomplexityresearchersinthe eld. RANDOM'98,heldattheUniversityofBarcelona(UPC),October8{10,1998, isthesecondintheseries,afterBologna. This volume contains all contributed papers accepted for presentation at theworkshop,togetherwithinvitedlecturesbyJosepD az(UPCBarcelona), AlanM. Frieze(CarnegieMellonU. ),MichaelLuby(ICSIBerkeley),andEmo Welzl(ETHZuric .. h). Thecontributedpaperswereselectedoutofseveraldozen submissions received in response to the call for papers. All papers published intheworkshopproceedingswereselectedbytheprogramcommitteeonthe basisofrefereereports. Considerablee ortwasdevotedtotheevaluationofthe submissionsbytheprogramcommitteeandanumberofotherreferees. Extensive feedbackwasprovidedtoauthorsasaresult,whichwehopehasprovenhelpful tothem. Wewouldliketothankalloftheauthorswhorespondedtothecallforpapers, ourinvitedspeakers,thereferees,andthemembersoftheprogramcommittee: MichaelLuby,Chair,ICSIBerkeley AndreiBroder,DigitalSystemsResearchCenter BernardChazelle,PrincetonU. AndreaClementi,U. ofRome AnnaKarlin,U. ofWashington RichardKarp,U. ofWashington ClaireKenyon,U. ofParisSud MichaelMitzenmacher,DigitalSystemsResearchCenter RajeevMotwani,StanfordU. PrabhakarRaghavan,IBM MariaSerna,UPCBarcelona AlistairSinclair,U. ofCalifornia,Berkeley MadhuSudan,MIT AviWigderson,HebrewU. PeterWinkler,BellLabs WegratefullyacknowledgesupportfromtheEuropeanAssociationINTAS, theComissionatperaUniversitatsiRecerca{GeneralitatdeCatalunya,and Universitat Polit ecnica de Catalunya. Finally, we would like to thank Helena Martinez,CarmeAlvarez,ConradoMartinez,andJordiPetitiSilvestrefortheir helpinthepreparationofthemeeting. August1998 MichaelLuby,Jos eD. P. Rolim,MariaJ. Serna Contents Invited Paper Disjoint Paths in Expander Graphs via Random Walks: A Short Survey 1 AlanM. Frieze RegularPapers A Derandomization Using Min-Wise Independent Permutations 15 AndreiZ. Broder,MosesCharikarandMichaelMitzenmacher An Algorithmic Embedding of Graphs via Perfect Matchings 25 VojtechR.. odl,AndrzejRucin 'skiandMichelleWagner Deterministic Hypergraph Coloring and Its Applications 35 Chi-JenLu On the De-randomization of Space-Bounded Computations 47 RoyArmoni Talagrand's Inequality and Locality in Distributed Computing 60 DevdattP. Dubhashi On-Line Bin-Stretching 71 YossiAzarandOdedRegev Combinatorial Linear Programming: Geometry Can Help 82 BerndGar .. tner A Note on Bounding the Mixing Time by Linear Programming 97 AbrahamSharell Robotic Exploration, Brownian Motion and Electrical Resistance 116 IsraelA. Wagner,MichaelLindenbaumandAlfredM. Bruckstein Fringe Analysis of Synchronized Parallel Algorithms on 2-3 Trees 131 RicardoBaeza-Yates,JoaquimGabarro 'andXavierMesseguer On Balls and Bins with Deletions 145 RichardCole,AlanFrieze,BruceM. Maggs,MichaelMitzenmacher Andr'eaW. Richa,RameshK.

This book constitutes the refereed proceedings of the International Workshop on Approximation Algorithms for Combinatorical Optimization, APPROX'98, held in conjunction with ICALP'98 in Aalborg, Denmark, in July 1998.
The volume presents 14 revised full papers together with three invited papers selected from 37 submissions. The papers address the design and analysis of approximation algorithms, inapproximability results, on-line problems, randomization techniques, average-case analysis, approximation classes, scheduling problems, routing and flow problems, coloring and partitioning, cuts and connectivity, packing and covering, geometric problems, network design, and various applications.

This book constitutes the refereed proceedings of the 5th International Symposium on Solving Irregularly Structured Problems in Parallel, IRREGULAR'98, held in Berkeley, California, in August 1998.
The 26 revised full papers presented were carefully reviewed and selected for inclusion from several dozen submissions. Also included are abstracts of four invited talks and 6 invited presentations given during minisymposia held in parallel. The book presents a unique overview on algorithmic, applicational, and systems aspects arising in the development of efficient parallel solutions to irregularly structured problems.

This book constitutes the refereed proceedings of 10 international workshops held in conjunction with the merged 1998 IPPS/SPDP symposia, held in Orlando, Florida, US in March/April 1998. The volume comprises 118 revised full papers presenting cutting-edge research or work in progress.
In accordance with the workshops covered, the papers are organized in topical sections on reconfigurable architectures, run-time systems for parallel programming, biologically inspired solutions to parallel processing problems, randomized parallel computing, solving combinatorial optimization problems in parallel, PC based networks of workstations, fault-tolerant parallel and distributed systems, formal methods for parallel programming, embedded HPC systems and applications, and parallel and distributed real-time systems.

This book constitutes the refereed proceedings of the International Workshop on Randomization and Approximation Techniques in Computer Science, RANDOM'97, held as a satelite meeting of ICALP'97, in Bologna, Italy, in July 1997.
The volume presents 14 thoroughly revised full papers selected from 37 submissions; also included are four invited contributions by leading researchers. The book focuses on algorithms and complexity aspects arising in the development of efficient randomized solutions to computationally difficult problems. The papers are organized in sections on approximation, randomness, algorithms, and complexity.

This book constitutes the refereed proceedings of the Third International Workshop on Parallel Algorithms for Irregularly Structured Problems, IRREGULAR '96, held in Santa Barbara, California, in August 1996.
The volume presents 28 revised full papers selected from 51 submissions; also included are one full invited paper by Torben Hagerup and abstracts of four other invited talks. The papers are organized in topical sections on sparse matrix problems, partitioning and domain composition, irregular applications, communication and synchronization, systems support, and mapping and load balancing.

Efficient parallel solutions have been found to many problems. Some of them can be obtained automatically from sequential programs, using compilers. However, there is a large class of problems - irregular problems - that lack efficient solutions. IRREGULAR 94 - a workshop and summer school organized in Geneva - addressed the problems associated with the derivation of efficient solutions to irregular problems. This book, which is based on the workshop, draws on the contributions of outstanding scientists to present the state of the art in irregular problems, covering aspects ranging from scientific computing, discrete optimization, and automatic extraction of parallelism. Audience: This first book on parallel algorithms for irregular problems is of interest to advanced graduate students and researchers in parallel computer science.

This book presents the proceedings of the Second International Workshop on Parallel Algorithms for Irregularly Structured Problems, IRREGULAR '95, held in Lyon, France in September 1995. This workshop series addresses issues related to deriving efficient parallel solutions to irregularly structured problems and aims at fostering cooperation between practitioners and theoreticians in the field.
Besides three invited papers, 20 full papers and eight short contributions are presented, all selected during a highly competitive refereeing process; the volume is organized in sections on programming methods and compiling techniques, mapping and scheduling, applications, and optimization.