{"title":"Improved Cheeger's Inequality and Analysis of Local Graph Partitioning using Vertex Expansion and Expansion Profile","authors":"T. C. Kwok, L. Lau, Y. Lee","doi":"10.1137/16M1079816","DOIUrl":"https://doi.org/10.1137/16M1079816","url":null,"abstract":"We prove two generalizations of the Cheeger's inequality. The first generalization relates the second eigenvalue to the edge expansion and the vertex expansion of the graph G, [EQUATION] where pV(G) denotes the robust vertex expansion of G and p(G) denotes the edge expansion of G. The second generalization relates the second eigenvalue to the edge expansion and the expansion profile of G, for all k ≥ 2, [EQUATION] where pk(G) denotes the k-way expansion of G. These show that the spectral partitioning algorithm has better performance guarantees when pV(G) is large (e.g. planted random instances) or pk(G) is large (instances with few disjoint non-expanding sets). Both bounds are tight up to a constant factor. Our approach is based on a method to analyze solutions of Laplacian systems, and this allows us to extend the results to local graph partitioning algorithms. In particular, we show that our approach can be used to analyze personal pagerank vectors, and to give a local graph partitioning algorithm for the small-set expansion problem with performance guarantees similar to the generalizations of Cheeger's inequality. We also present a spectral approach to prove similar results for the truncated random walk algorithm. These show that local graph partitioning algorithms almost match the performance of the spectral partitioning algorithm, with the additional advantages that they apply to the small-set expansion problem and their running time could be sublinear. Our techniques provide common approaches to analyze the spectral partitioning algorithm and local graph partitioning algorithms.","PeriodicalId":160227,"journal":{"name":"SIAM journal on computing (Print)","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114754456","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":"Capacity of Interactive Communication over Erasure Channels and Channels with Feedback","authors":"R. Gelles, Bernhard Haeupler","doi":"10.1137/15M1052202","DOIUrl":"https://doi.org/10.1137/15M1052202","url":null,"abstract":"We consider interactive communication performed over two simple types of noisy channels: binary error channels with noiseless feedback and binary erasure channels. In both cases, the noise model is adversarial. Assuming at most e-fraction of the bits can be corrupted, we show coding schemes that simulate any alternating interactive protocol with rate 1 − Θ(H(e)). All our simulations are simple, randomized, and computationally efficient.The rates of our coding schemes stand in contrast to the interactive communication rates supported by random or adversarial error channels without feedback, for which the best known coding schemes achieve rates of 1 − Θ([EQUATION]e) and 1 − Θ([EQUATION]e log log 1/e), respectively. As these rates are conjectured to be optimal, our result implies a large asymptotic gap between interactive communication rate over noisy channels with and without feedback. Such a gap has no equivalent in the standard one-way communication setting.","PeriodicalId":160227,"journal":{"name":"SIAM journal on computing (Print)","volume":"50 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124925961","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":"Partitioning Well-Clustered Graphs: Spectral Clustering Works!","authors":"Richard Peng, He Sun, Luca Zanetti","doi":"10.1137/15M1047209","DOIUrl":"https://doi.org/10.1137/15M1047209","url":null,"abstract":"In this paper we study variants of the widely used spectral clustering that partitions a graph into $k$ clusters by (1) embedding the vertices of a graph into a low-dimensional space using the bottom eigenvectors of the Laplacian matrix and (2) grouping the embedded points into $k$ clusters via $k$-means algorithms. We show that, for a wide class of graphs, spectral clustering gives a good approximation of the optimal clustering. While this approach was proposed in the early 1990s and has comprehensive applications, prior to our work similar results were known only for graphs generated from stochastic models. We also give a nearly linear time algorithm for partitioning well-clustered graphs based on computing a matrix exponential and approximate nearest neighbor data structures.","PeriodicalId":160227,"journal":{"name":"SIAM journal on computing (Print)","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2014-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126556305","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":"A Size-Sensitive Discrepancy Bound for Set Systems of Bounded Primal Shatter Dimension","authors":"Esther Ezra","doi":"10.1137/140977746","DOIUrl":"https://doi.org/10.1137/140977746","url":null,"abstract":"Let (X, S) be a set system on an n-point set X. The discrepancy of S is defined as the minimum of the largest deviation from an even split, over all subsets of S e S and two-colorings χ on X. We consider the scenario where, for any subset X' ⊆ X of size m ≤ n and for any parameter 1 ≤ k ≤ m, the number of restrictions of the sets of S to X' of size at most k is only O(md1kd-d1), for fixed integers d > 0 and 1 ≤ d1 ≤ d (this generalizes the standard notion of bounded primal shatter dimension when d1 = d). In this case we show that there exists a coloring χ with discrepancy bound O*(|S|1/2-d1/(2d)n(d1-1)/(2d)), for each S e S, where O*(·) hides a polylogarithmic factor in n. This bound is tight up to a polylogarithmic factor [21, 23] and the corresponding coloring χ can be computed in expected polynomial time using the very recent machinery of Lovett and Meka for constructive discrepancy minimization [20]. Our bound improves and generalizes the bounds obtained from the machinery of Har-Peled and Sharir [15] (and the follow-up work in [27]) for points and halfspaces in d-space for d ≥ 3. Last but not least, we show that our bound yields improved bounds for the size of relative (e, δ)-approximations for set systems of the above kind.","PeriodicalId":160227,"journal":{"name":"SIAM journal on computing (Print)","volume":"115 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122963703","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":"Circumventing the Price of Anarchy: Leading Dynamics to Good Behavior","authors":"Maria-Florina Balcan, Avrim Blum, Y. Mansour","doi":"10.1137/110821317","DOIUrl":"https://doi.org/10.1137/110821317","url":null,"abstract":"Many natural games have a dramatic difference between the quality of their best and worst Nash equilibria, even in pure strategies. Yet, nearly all results to date on dynamics in games show only convergence to some equilibrium, especially within a polynomial number of steps. In this work we initiate a theory of how well-motivated multiagent dynamics can make use of global information about the game---which might be common knowledge or injected into the system by a helpful central agency---and show that in a wide range of interesting games this can allow the dynamics to quickly reach (within a polynomial number of steps) states of cost comparable to the best Nash equilibrium. We present several natural models for dynamics that can use such additional information and analyze their ability to reach low-cost states for two important and widely studied classes of potential games: network design with fair cost-sharing and party affiliation games (which include consensus and cut games). From the perspective of a...","PeriodicalId":160227,"journal":{"name":"SIAM journal on computing (Print)","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122694572","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}
Tobias Brunsch, Kamiel Cornelissen, B. Manthey, Heiko Röglin, Clemens Rösner
{"title":"Smoothed Analysis of the Successive Shortest Path Algorithm","authors":"Tobias Brunsch, Kamiel Cornelissen, B. Manthey, Heiko Röglin, Clemens Rösner","doi":"10.1137/140989893","DOIUrl":"https://doi.org/10.1137/140989893","url":null,"abstract":"The minimum-cost flow problem is a classic problem in combinatorial optimization with various applications. Several pseudo-polynomial, polynomial, and strongly polynomial algorithms have been developed in the past decades, and it seems that both the problem and the algorithms are well understood. However, some of the algorithms' running times observed in empirical studies contrast the running times obtained by worst-case analysis not only in the order of magnitude but also in the ranking when compared to each other. For example, the Successive Shortest Path (SSP) algorithm, which has an exponential worst-case running time, seems to outperform the strongly polynomial Minimum-Mean Cycle Canceling algorithm. To explain this discrepancy, we study the SSP algorithm in the framework of smoothed analysis and establish a bound of O(mnφ(m + n log n)) for its smoothed running time. This shows that worst-case instances for the SSP algorithm are not robust and unlikely to be encountered in practice.","PeriodicalId":160227,"journal":{"name":"SIAM journal on computing (Print)","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132139833","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":"Skew Bisubmodularity and Valued CSPs","authors":"Anna Huber, A. Krokhin, Robert Powell","doi":"10.1137/120893549","DOIUrl":"https://doi.org/10.1137/120893549","url":null,"abstract":"An instance of the (finite-)valued constraint satisfaction problem (VCSP) is given by a finite set of variables, a finite domain of values, and a sum of (rational-valued) functions, with each function depending on a subset of the variables. The goal is to find an assignment of values to the variables that minimizes the sum. We study (assuming that ${PTIME}neq{NP}$) how the complexity of this very general problem depends on the functions allowed in the instances. The case when the variables can take only two values was classified by Cohen et al.: essentially, submodular functions give rise to the only tractable case, and any non--submodular function can be used to express, in a certain specific sense, the NP-hard Max Cut problem. We investigate the case when the variables can take three values. We identify a new infinite family of conditions that includes bisubmodularity as a special case and which can collectively be called skew bisubmodularity. By a recent result of Thapper and Živný, this condition imp...","PeriodicalId":160227,"journal":{"name":"SIAM journal on computing (Print)","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128690422","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 Almost Optimal Algorithm for Computing Nonnegative Rank","authors":"Ankur Moitra","doi":"10.1137/140990139","DOIUrl":"https://doi.org/10.1137/140990139","url":null,"abstract":"Here, we give an algorithm for deciding if the nonnegative rank of a matrix $M$ of dimension $m times n$ is at most $r$ which runs in time $(nm)^{O(r^2)}$. This is the first exact algorithm that runs in time singly exponential in $r$. This algorithm (and earlier algorithms) are built on methods for finding a solution to a system of polynomial inequalities (if one exists). Notably, the best algorithms for this task run in time exponential in the number of variables but polynomial in all of the other parameters (the number of inequalities and the maximum degree). Hence, these algorithms motivate natural algebraic questions whose solution have immediate algorithmic implications: How many variables do we need to represent the decision problem, and does $M$ have nonnegative rank at most $r$? A naive formulation uses $nr + mr$ variables and yields an algorithm that is exponential in $n$ and $m$ even for constant $r$. Arora et al. [Proceedings of STOC, 2012, pp. 145--162] recently reduced the number of variable...","PeriodicalId":160227,"journal":{"name":"SIAM journal on computing (Print)","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2013-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122319692","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}
K. Clarkson, P. Drineas, M. Magdon-Ismail, Michael W. Mahoney, Xiangrui Meng, David P. Woodruff
{"title":"The Fast Cauchy Transform and Faster Robust Linear Regression","authors":"K. Clarkson, P. Drineas, M. Magdon-Ismail, Michael W. Mahoney, Xiangrui Meng, David P. Woodruff","doi":"10.1137/140963698","DOIUrl":"https://doi.org/10.1137/140963698","url":null,"abstract":"@ are a coreset for the problem, consisting of sampled and rescaled rows of A and b; and s is independent of n and polynomial in d. Our results improve on the best previous algorithms when n G d, for all p e [1, ∞) except p = 2; in particular, they improve the O(nd1.376+) running time of Sohler and Woodruff (STOC, 2011) for p = 1, that uses asymptotically fast matrix multiplication, and the O(nd5 log n) time of Dasgupta et al. (SICOMP, 2009) for general p, that uses ellipsoidal rounding. We also provide a suite of improved results for finding well-conditioned bases via ellipsoidal rounding, illustrating tradeoffs between running time and conditioning quality, including a one-pass conditioning algorithm for general ep problems. \u0000 \u0000To complement this theory, we provide a detailed empirical evaluation of implementations of our algorithms for p = 1, comparing them with several related algorithms. Among other things, our empirical results clearly show that, in the asymptotic regime, the theory is a very good guide to the practical performance of these algorithms. Our algorithms use our faster constructions of well-conditioned bases for ep spaces and, for p = 1, a fast subspace embedding of independent interest that we call the Fast Cauchy Transform: a matrix Π:","PeriodicalId":160227,"journal":{"name":"SIAM journal on computing (Print)","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133603494","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":"Restricted Isometry of Fourier Matrices and List Decodability of Random Linear Codes","authors":"Mahdi Cheraghchi, V. Guruswami, A. Velingker","doi":"10.1137/120896773","DOIUrl":"https://doi.org/10.1137/120896773","url":null,"abstract":"@q, with probability arbitrarily close to 1, is list decodable at radius 1--1/q -- e with list size L = O(1/e2) and rate R = Ωq(e2/(log3(1/e))). Up to the polylogarithmic factor in 1/e and constant factors depending on q, this matches the lower bound L = Ωq(1/e2) for the list size and upper bound R = Oq(e2) for the rate. Previously only existence (and not abundance) of such codes was known for the special case q = 2 (Guruswami, Hastad, Sudan and Zuckerman, 2002).In order to obtain our result, we employ a relaxed version of the well known Johnson bound on list decoding that translates the average Hamming distance between codewords to list decoding guarantees. We furthermore prove that the desired average-distance guarantees hold for a code provided that a natural complex matrix encoding the codewords satisfies the Restricted Isometry Property with respect to the Euclidean norm (RIP-2). For the case of random binary linear codes, this matrix coincides with a random submatrix of the Hadamard-Walsh transform matrix that is well studied in the compressed sensing literature.Finally we improve the analysis of Rudelson and Vershynin (2008) on the number of random frequency samples required for exact reconstruction of k-sparse signals of length N. Specifically we improve the number of samples from O(k log (N) log2 (k)(log k+log log N)) to O(k log(N) log3(k)). The proof involves bounding the expected supremum of a related Gaussian process by using an improved analysis of the metric defined by the process. This improvement is crucial for our application in list decoding.","PeriodicalId":160227,"journal":{"name":"SIAM journal on computing (Print)","volume":"235 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2012-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132586041","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}