Proceedings of the twenty-fifth annual ACM symposium on Theory of Computing最新文献

{"title":"Approximate load balancing on dynamic and asynchronous networks","authors":"W. Aiello, B. Awerbuch, B. Maggs, Satish Rao","doi":"10.1145/167088.167250","DOIUrl":"https://doi.org/10.1145/167088.167250","url":null,"abstract":"This paper presents a simple local algorithm for load balancing in a distributed network. The algorithm makes no assumption about the structure of the network. It can be executed on a synchronous network with fixed topology, a synchronous network with dynamically changing topology, or an asynchronous network. It works quickly and balances well when the network has an expansion property. In particular, we show that in ann-node network with maximumdegree d whose live edges, at every time step, form a -expander, the algorithm will balance the load to within an additive O(d logn= ) term in O( log(n )= ) time, where is the initial imbalance. The algorithm improves upon previous approaches that yield O(n) time bounds in dynamic and asynchronous networks.","PeriodicalId":280602,"journal":{"name":"Proceedings of the twenty-fifth annual ACM symposium on Theory of Computing","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122882396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Asynchronous secure computation","authors":"M. Ben-Or, R. Canetti, Oded Goldreich","doi":"10.1145/167088.167109","DOIUrl":"https://doi.org/10.1145/167088.167109","url":null,"abstract":"We initiate a study of security in asynchronous networks. We consider a completely asynchronous network where every two parties are connected via a private channel, and some of the parties may be faulty. We start by defining secure computation in this model. Our definition adapts the underlying principles of defining security (i.e., comparing the computation to a computation in the presence of a trusted party) to the asynchronous model. In particular, our definition takes into account the fact that the computation must be completed even if we never hear from the faulty parties. Next, we show that whatever can be securely computed in an asynchronous network in the presence of a trusted party, can be securely computed in a network in which no such trusted party exists. We distinguish two types of faults. In case of Fail-Stop faults, our construction is valid as long as the faulty parties constitute less than a thzr-d of the parties in the network. In case of general (i.e., Byzantine) faults, our construction requires that the faulty parties are less than a fourth fraction. In both cases, the resilience of our construction is optimal. Our construction generalizes known synchronous constructions by Ben-Or, Goldwasser and Wigderson. In addition, we introduce and implement several new asynchronous primitives. Among these, we note an errorless asynchronous verifiable secret sharing scheme, an asynchronous agreement on a large set that is contained in the dynamical y growing inputs of all non-faulty parties, and an on-line error-correcting procedure. * email: benor@cs.huji.ac.il t ~~ail.. canetti@tx .technion.ac.il %email: odedrfiks.technion. ac.il. Supported by grant no. 8900312 from the United States — Israel Binational Science Foundation, Jerusalem, Israel Permission to copy without fee all or part of this material ia granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appaar, and notice is given that copying is by permission of the Association for Computing Machinery. To copy otherwiee, or to republish, requiree a fee and/or specific permission. 25th ACM STOC ‘93-5 /93/CA, USA G 1993 ACM 0-89791 -591 -7/93 /0005 [0052 . ..$1 .50 Computer Science Dept. of Computer Science","PeriodicalId":280602,"journal":{"name":"Proceedings of the twenty-fifth annual ACM symposium on Theory of Computing","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126290528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparison-based search in the presence of errors","authors":"Ryan S. Borgstrom, S. R. Kosaraju","doi":"10.1145/167088.167129","DOIUrl":"https://doi.org/10.1145/167088.167129","url":null,"abstract":"The classic problem of searching an ordered list becomes more complicated when the answers to queries are not reliable. In the prefix-bounded error model, the number of incorrect responses at no point exceeds r times the number of questions, where r is a fixed positive fraction strictly less than ~. We present efficient algorithms for searching in this error model, and we also establish nontrivial lower bounds for sorting, maxima finding, and related problems.","PeriodicalId":280602,"journal":{"name":"Proceedings of the twenty-fifth annual ACM symposium on Theory of Computing","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117027805","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An Õ(n2) algorithm for minimum cuts","authors":"David R Karger, C. Stein","doi":"10.1145/167088.167281","DOIUrl":"https://doi.org/10.1145/167088.167281","url":null,"abstract":"A minimum cut is a set of edges of minimum weight whose removal disconnects a given graph. Minimum cut algorithms historically applied duality with maximum flows and thus had the same 0 (inn) running time as maximum flow algorithms. More recent algorithms which are not based on maximum flows also require fl (inn) time. In this paper, we present the first algorithm that breaks the tl(mn) “max-flow barrier” for finding minimum cuts in weighted undirected graphs. We give a strongly polynomial randomized algorithm which finds a minimum cut with high probability in 0(n2 log3 n) time. This suggests that the rein-cut problem might be fundamentally easier to solve than the maximum flow problem. Our algorithm can be implemented in 72JUC using only nz processors—this is the first efficient 7UfC algorithm for the rein-cut problem. Our algorithm is simple and uses no complicated data structures.","PeriodicalId":280602,"journal":{"name":"Proceedings of the twenty-fifth annual ACM symposium on Theory of Computing","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129035064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"What can be computed locally?","authors":"M. Naor, L. Stockmeyer","doi":"10.1145/167088.167149","DOIUrl":"https://doi.org/10.1145/167088.167149","url":null,"abstract":"The purpose of this paper is a study of computation that can be done locally in a distributed network, where \"locally\" means within time (or distance) independent of the size of the network. Locally checkable labeling (LCL) problems are considered, where the legality of a labeling can be checked locally (e.g., coloring). The results include the following: \u0000There are nontrivial LCL problems that have local algorithms. \u0000There is a variant of the dining philosophers problem that can be solved locally. \u0000Randomization cannot make an LCL problem local; i.e., if a problem has a local randomized algorithm then it has a local deterministic algorithm. \u0000It is undecidable, in general, whether a given LCL has a local algorithm. \u0000However, it is decidable whether a given LCL has an algorithm that operates in a given time $t$. \u0000Any LCL problem that has a local algorithm has one that is order-invariant (the algorithm depends only on the order of the processor IDs).","PeriodicalId":280602,"journal":{"name":"Proceedings of the twenty-fifth annual ACM symposium on Theory of Computing","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126963552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"How to use expert advice","authors":"N. Cesa-Bianchi, Y. Freund, D. Helmbold, D. Haussler, R. Schapire, Manfred K. Warmuth","doi":"10.1145/167088.167198","DOIUrl":"https://doi.org/10.1145/167088.167198","url":null,"abstract":"We analyze algorithms that predict a binary value by combining the predictions of several prediction strategies, called `experts''. Our analysis is for worst-case situations, i.e., we make no assumptions about the way the sequence of bits to be predicted is generated. We measure the performance of the algorithm by the difference between the expected number of mistakes it makes on the bit sequence and the expected number of mistakes made by the best expert on this sequence, where the expectation is taken with respect to the randomization in the predictions. We show that the minimum achievable difference is on the order of the square root of the number of mistakes of the best expert, and we give efficient algorithms that achieve this. Our upper and lower bounds have matching leading constants in most cases. We then show how this leads to certain kinds of pattern recognition/learning algorithms with performance bounds that improve on the best results currently known in this context. We also extend our analysis to the case in which log loss is used instead of the expected number of mistakes.","PeriodicalId":280602,"journal":{"name":"Proceedings of the twenty-fifth annual ACM symposium on Theory of Computing","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128906179","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Locality based graph coloring","authors":"M. Szegedy, S. Vishwanathan","doi":"10.1145/167088.167156","DOIUrl":"https://doi.org/10.1145/167088.167156","url":null,"abstract":"We study the problem of locality based graph coloring. This problem is motivated by the problem of assigning time slots for broadcast in mobile packet radio networks. This problem has also been studied in the context of distributed and parallel graph coloring [4, 6, 9, 8]. In this problem, one has to design a coloring algorithm that assigns a color to a vertex based on the label of the vertex and the labels on its neighbors. Linial proved an upper bound of O(A2 log n) and a lower bound of fl(log log n) on the number of colors needed to locally color an n-vertex graph with maximum vertex degree A [9, 8]. His main motivation was that repeated application of local coloring gives a fast algorithm for distributed coloring. He proved that one could get a A2 coloring in O(log* n) steps this way. In this paper we improve upon the bounds for the problem of local coloring. Using a new characterization in terms of a family of set systems we design a randomized algorithm for the problem and prove an upper bound of O(A. 2A log log n). An important question left open in Linial’s paper was the case of large A. The best lower bound was A + 1. Linial observed that a result of Erdos, Frankl and Furedi implied that his method cannot be applied to reduce the number of colors to below (A~2). We obtain lower bounds that match the upper bounds within a factor that is poly-logarithmic in terms of these bounds. Of particular interest we have very precise bounds for the case when A > 2+. These bounds are useful to obtain a heuristic estimate on the *Researchsupported in part by Ketan Mulmuley’s Packard Fellowship. Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of tha Association for Computing Machinery. To copy otherwise, or to republish, requires a fee and/or specific permission. 25th ACM STOC ‘93-51931CA, LJSA","PeriodicalId":280602,"journal":{"name":"Proceedings of the twenty-fifth annual ACM symposium on Theory of Computing","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134480944","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"More deterministic simulation in logspace","authors":"N. Nisan, David Zuckerman","doi":"10.1145/167088.167162","DOIUrl":"https://doi.org/10.1145/167088.167162","url":null,"abstract":"We show that any randomized space(S) algorithm which uses only poly(S) random bits can be simulated deterministically in space(S), for S(n) ~ log n. Of independent interest is our main technical tool: a procedure which extracts randomness from a defective random source using a small additional number of truly random bits.","PeriodicalId":280602,"journal":{"name":"Proceedings of the twenty-fifth annual ACM symposium on Theory of Computing","volume":"116 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128021126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Space-efficient scheduling of multithreaded computations","authors":"R. Blumofe, C. Leiserson","doi":"10.1145/167088.167196","DOIUrl":"https://doi.org/10.1145/167088.167196","url":null,"abstract":"This paper considers the problem of scheduling dynamic parallel computations to achieve linear speedup without using significantly more space per processor than that required for a single-processor execution. Utilizing a new graph-theoretic model of multithreaded computation, execution efficiency is quantified by three important measures: T1 is the time required for executing the computation on a 1 processor, $T_infty$ is the time required by an infinite number of processors, and S1 is the space required to execute the computation on a 1 processor. A computation executed on P processors is time-efficient if the time is $O(T_1/P + T_infty)$, that is, it achieves linear speedup when $P=O(T_1/T_infty)$, and it is space-efficient if it uses O(S1P) total space, that is, the space per processor is within a constant factor of that required for a 1-processor execution. \u0000The first result derived from this model shows that there exist multithreaded computations such that no execution schedule can simultaneously achieve efficient time and efficient space. But by restricting attention to \"strict\" computations---those in which all arguments to a procedure must be available before the procedure can be invoked---much more positive results are obtainable. Specifically, for any strict multithreaded computation, a simple online algorithm can compute a schedule that is both time-efficient and space-efficient. Unfortunately, because the algorithm uses a global queue, the overhead of computing the schedule can be substantial. This problem is overcome by a decentralized algorithm that can compute and execute a P-processor schedule online in expected time $O(T_1/P + T_inftylg P)$ and worst-case space $O(S_1Plg P)$, including overhead costs.","PeriodicalId":280602,"journal":{"name":"Proceedings of the twenty-fifth annual ACM symposium on Theory of Computing","volume":"138 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115691658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mapping the genome: some combinatorial problems arising in molecular biology","authors":"R. Karp","doi":"10.1145/167088.167170","DOIUrl":"https://doi.org/10.1145/167088.167170","url":null,"abstract":"The ultimate goal of the Human Genome Project and many other efforts in molecular biology is to sequence the chromosomal DNA of humans and other species and elucidate the genetic information contained therein. A less ambitious intermediate goal is to construct physical maps of our 23 pairs of chromosomes. A physical map specifies the locations of markers identifiable fragments of DNA along the DNA molecule. These markers provide a kind of random access to the linear DNA molecule. To locate a feature of interest such as a gene, an experimenter can start at a marker that is known to be close to the gene and “walk” along the DNA until the gene is identified.","PeriodicalId":280602,"journal":{"name":"Proceedings of the twenty-fifth annual ACM symposium on Theory of Computing","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1993-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116619752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}