Pub Date : 2001-10-14DOI: 10.1109/SFCS.2001.959935
A. Srinivasan
We consider a family of distributions on fixed-weight vectors in {0, 1}/sup t/; these distributions enjoy certain negative correlation properties and also satisfy pre-specified conditions on their marginal distributions. We show the existence of such families, and present a linear-time algorithm to sample from them. This yields improved approximation algorithms for the following problems: (a) low-congestion multi-path routing; (b) maximum coverage versions of set cover; (c) partial vertex cover problems for bounded-degree graphs; and (d) the Group Steiner Tree problem. For (a) and (b), the improvement is in the approximation ratio; for (c), we show how to speedup existing approximation algorithms while preserving the best-known approximation ratio; we also improve the approximation ratio for certain families of instances of unbounded degree. For (d), we derive an approximation algorithm whose approximation guarantee is at least as good as what is known; our algorithm is shown to have a better approximation guarantee for the worst known input families for existing algorithms.
{"title":"Distributions on level-sets with applications to approximation algorithms","authors":"A. Srinivasan","doi":"10.1109/SFCS.2001.959935","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959935","url":null,"abstract":"We consider a family of distributions on fixed-weight vectors in {0, 1}/sup t/; these distributions enjoy certain negative correlation properties and also satisfy pre-specified conditions on their marginal distributions. We show the existence of such families, and present a linear-time algorithm to sample from them. This yields improved approximation algorithms for the following problems: (a) low-congestion multi-path routing; (b) maximum coverage versions of set cover; (c) partial vertex cover problems for bounded-degree graphs; and (d) the Group Steiner Tree problem. For (a) and (b), the improvement is in the approximation ratio; for (c), we show how to speedup existing approximation algorithms while preserving the best-known approximation ratio; we also improve the approximation ratio for certain families of instances of unbounded degree. For (d), we derive an approximation algorithm whose approximation guarantee is at least as good as what is known; our algorithm is shown to have a better approximation guarantee for the worst known input families for existing algorithms.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134421271","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}
Pub Date : 2001-10-14DOI: 10.1109/SFCS.2001.959936
Subhash Khot
The author presents improved inapproximability results for three problems: the problem of finding the maximum clique size in a graph, the problem of finding the chromatic number of a graph, and the problem of coloring a graph with a small chromatic number with a small number of colors. J. Hastad's (1996) result shows that the maximum clique size in a graph with n vertices is inapproximable in polynomial time within a factor n/sup 1-/spl epsi// or arbitrarily small constant /spl epsi/>0 unless NP=ZPP. We aim at getting the best subconstant value of /spl epsi/ in Hastad's result. We prove that clique size is inapproximable within a factor n/2((log n))/sup 1-y/ corresponding to /spl epsi/=1/(log n)/sup /spl gamma// for some constant /spl gamma/>0 unless NP/spl sube/ZPTIME(2((log n))/sup O(1)/). This improves the previous best inapproximability factor of n/2/sup O(log n//spl radic/log log n)/ (corresponding to /spl epsi/=O(1//spl radic/log log n)) due to L. Engebretsen and J. Holmerin (2000). A similar result is obtained for the problem of approximating chromatic number of a graph. We also present a new hardness result for approximate graph coloring. We show that for all sufficiently large constants k, it is NP-hard to color a k-colorable graph with k/sup 1/25 (log k)/ colors. This improves a result of M. Furer (1995) that for arbitrarily small constant /spl epsi/>0, for sufficiently large constants k, it is hard to color a k-colorable graph with k/sup 3/2-/spl epsi// colors.
{"title":"Improved inapproximability results for MaxClique, chromatic number and approximate graph coloring","authors":"Subhash Khot","doi":"10.1109/SFCS.2001.959936","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959936","url":null,"abstract":"The author presents improved inapproximability results for three problems: the problem of finding the maximum clique size in a graph, the problem of finding the chromatic number of a graph, and the problem of coloring a graph with a small chromatic number with a small number of colors. J. Hastad's (1996) result shows that the maximum clique size in a graph with n vertices is inapproximable in polynomial time within a factor n/sup 1-/spl epsi// or arbitrarily small constant /spl epsi/>0 unless NP=ZPP. We aim at getting the best subconstant value of /spl epsi/ in Hastad's result. We prove that clique size is inapproximable within a factor n/2((log n))/sup 1-y/ corresponding to /spl epsi/=1/(log n)/sup /spl gamma// for some constant /spl gamma/>0 unless NP/spl sube/ZPTIME(2((log n))/sup O(1)/). This improves the previous best inapproximability factor of n/2/sup O(log n//spl radic/log log n)/ (corresponding to /spl epsi/=O(1//spl radic/log log n)) due to L. Engebretsen and J. Holmerin (2000). A similar result is obtained for the problem of approximating chromatic number of a graph. We also present a new hardness result for approximate graph coloring. We show that for all sufficiently large constants k, it is NP-hard to color a k-colorable graph with k/sup 1/25 (log k)/ colors. This improves a result of M. Furer (1995) that for arbitrarily small constant /spl epsi/>0, for sufficiently large constants k, it is hard to color a k-colorable graph with k/sup 3/2-/spl epsi// colors.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"179 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133337974","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}
Pub Date : 2001-10-14DOI: 10.1109/SFCS.2001.959901
Amit Chakrabarti, Yaoyun Shi, Anthony Wirth, A. Yao
Given m copies of the same problem, does it take m times the amount of resources to solve these m problems? This is the direct sum problem, a fundamental question that has been studied in many computational models. We study this question in the simultaneous message (SM) model of communication introduced by A.C. Yao (1979). The equality problem for n-bit strings is well known to have SM complexity /spl Theta/(/spl radic/n). We prove that solving m copies of the problem has complexity /spl Omega/(m/spl radic/n); the best lower bound provable using previously known techniques is /spl Omega/(/spl radic/(mn)). We also prove similar lower bounds on certain Boolean combinations of multiple copies of the equality function. These results can be generalized to a broader class of functions. We introduce a new notion of informational complexity which is related to SM complexity and has nice direct sum properties. This notion is used as a tool to prove the above results; it appears to be quite powerful and may be of independent interest.
{"title":"Informational complexity and the direct sum problem for simultaneous message complexity","authors":"Amit Chakrabarti, Yaoyun Shi, Anthony Wirth, A. Yao","doi":"10.1109/SFCS.2001.959901","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959901","url":null,"abstract":"Given m copies of the same problem, does it take m times the amount of resources to solve these m problems? This is the direct sum problem, a fundamental question that has been studied in many computational models. We study this question in the simultaneous message (SM) model of communication introduced by A.C. Yao (1979). The equality problem for n-bit strings is well known to have SM complexity /spl Theta/(/spl radic/n). We prove that solving m copies of the problem has complexity /spl Omega/(m/spl radic/n); the best lower bound provable using previously known techniques is /spl Omega/(/spl radic/(mn)). We also prove similar lower bounds on certain Boolean combinations of multiple copies of the equality function. These results can be generalized to a broader class of functions. We introduce a new notion of informational complexity which is related to SM complexity and has nice direct sum properties. This notion is used as a tool to prove the above results; it appears to be quite powerful and may be of independent interest.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"300 ","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120932705","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}
Pub Date : 2001-10-14DOI: 10.1109/SFCS.2001.959889
Anupam Gupta, Amit Kumar, R. Rastogi
MultiProtocol Label Switching (MPLS) is a routing model proposed by the IETF for the Internet, and is becoming widely popular. In this paper, we initiate a theoretical study of the routing model, and give routing algorithms and lower bounds in a variety of situations. We first study the routing problems on the line. We then build up our results from paths through trees to more general graphs. The basic technique to go to general graphs is that of finding a tree cover, which is a small set of subtrees of the graph such that for each pair of vertices, one of the trees contains a shortest (or near-shortest) path between them. The concept of tree covers appears to have many interesting applications.
{"title":"Traveling with a Pez dispenser (or, routing issues in MPLS)","authors":"Anupam Gupta, Amit Kumar, R. Rastogi","doi":"10.1109/SFCS.2001.959889","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959889","url":null,"abstract":"MultiProtocol Label Switching (MPLS) is a routing model proposed by the IETF for the Internet, and is becoming widely popular. In this paper, we initiate a theoretical study of the routing model, and give routing algorithms and lower bounds in a variety of situations. We first study the routing problems on the line. We then build up our results from paths through trees to more general graphs. The basic technique to go to general graphs is that of finding a tree cover, which is a small set of subtrees of the graph such that for each pair of vertices, one of the trees contains a shortest (or near-shortest) path between them. The concept of tree covers appears to have many interesting applications.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"72 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114523098","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}
Pub Date : 2001-10-14DOI: 10.1109/SFCS.2001.959921
P. Drineas, R. Kannan
Given an m ? n matrix A and an n ? p matrix B, we present 2 simple and intuitive algorithms to compute an approximation P to the product A ? B, with provable bounds for the norm of the "error matrix" P - A ? B. Both algorithms run in 0(mp+mn+np) time. In both algorithms, we randomly pick s = 0(1) columns of A to form an m ? s matrix S and the corresponding rows of B to form an s ? p matrix R. After scaling the columns of S and the rows of R, we multiply them together to obtain our approximation P. The choice of the probability distribution we use for picking the columns of A and the scaling are the crucial features which enable us to fairly elementary proofs of the error bounds. Our first algorithm can be implemented without storing the matrices A and B in Random Access Memory, provided we can make two passes through the matrices (stored in external memory). The second algorithm has a smaller bound on the 2-norm of the error matrix, but requires storage of A and B in RAM. We also present a fast algorithm that "describes" P as a sum of rank one matrices if B = AT.
{"title":"Fast Monte-Carlo algorithms for approximate matrix multiplication","authors":"P. Drineas, R. Kannan","doi":"10.1109/SFCS.2001.959921","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959921","url":null,"abstract":"Given an m ? n matrix A and an n ? p matrix B, we present 2 simple and intuitive algorithms to compute an approximation P to the product A ? B, with provable bounds for the norm of the \"error matrix\" P - A ? B. Both algorithms run in 0(mp+mn+np) time. In both algorithms, we randomly pick s = 0(1) columns of A to form an m ? s matrix S and the corresponding rows of B to form an s ? p matrix R. After scaling the columns of S and the rows of R, we multiply them together to obtain our approximation P. The choice of the probability distribution we use for picking the columns of A and the scaling are the crucial features which enable us to fairly elementary proofs of the error bounds. Our first algorithm can be implemented without storing the matrices A and B in Random Access Memory, provided we can make two passes through the matrices (stored in external memory). The second algorithm has a smaller bound on the 2-norm of the error matrix, but requires storage of A and B in RAM. We also present a fast algorithm that \"describes\" P as a sum of rank one matrices if B = AT.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"421 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132872857","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}
Pub Date : 2001-10-14DOI: 10.1109/SFCS.2001.959904
Hubert Comon-Lundh, Guillem Godoy, R. Nieuwenhuis
The confluence property of ground (i.e., variable-free) term rewrite systems (GTRS) is well-known to be decidable. This was proved independently by M. Dauchet et al. (1987; 1990) and by M. Oyamaguchi (1987) using tree automata techniques and ground tree transducer techniques (originated from this problem), yielding EXPTIME decision procedures (PSPACE for strings). Since then, it has been a well-known longstanding open question whether this bound is optimal. The authors give a polynomial-time algorithm for deciding the confluence of GTRS, and hence alsofor the particular case of suffix- and prefix string rewrite systems or Thue systems. We show that this bound is optimal for all these problems by proving PTIME-hardness for the string case. This result may have some impact on other areas of formal language theory, and in particular on the theory of tree automata.
众所周知，地面(即无变量)项重写系统(GTRS)的合流特性是可确定的。M. Dauchet et al. (1987;1990)和M. yamaguchi(1987)使用树自动机技术和地面树传感器技术(起源于这个问题)，产生EXPTIME决策程序(字符串的PSPACE)。从那以后，这个界限是否最优一直是一个众所周知的长期悬而未决的问题。作者给出了一个多项式时间算法来决定GTRS的合流，从而也适用于后缀和前缀字符串重写系统或Thue系统的特殊情况。我们通过证明弦的ptime -硬度来证明这个界对于所有这些问题都是最优的。这一结果可能会对形式语言理论的其他领域产生一些影响，特别是在树自动机理论方面。
{"title":"The confluence of ground term rewrite systems is decidable in polynomial time","authors":"Hubert Comon-Lundh, Guillem Godoy, R. Nieuwenhuis","doi":"10.1109/SFCS.2001.959904","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959904","url":null,"abstract":"The confluence property of ground (i.e., variable-free) term rewrite systems (GTRS) is well-known to be decidable. This was proved independently by M. Dauchet et al. (1987; 1990) and by M. Oyamaguchi (1987) using tree automata techniques and ground tree transducer techniques (originated from this problem), yielding EXPTIME decision procedures (PSPACE for strings). Since then, it has been a well-known longstanding open question whether this bound is optimal. The authors give a polynomial-time algorithm for deciding the confluence of GTRS, and hence alsofor the particular case of suffix- and prefix string rewrite systems or Thue systems. We show that this bound is optimal for all these problems by proving PTIME-hardness for the string case. This result may have some impact on other areas of formal language theory, and in particular on the theory of tree automata.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"11 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133986560","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}
Pub Date : 2001-10-14DOI: 10.1109/SFCS.2001.959924
Aaron Archer, É. Tardos
The authors show how to design truthful (dominant strategy) mechanisms for several combinatorial problems where each agent's secret data is naturally expressed by a single positive real number. The goal of the mechanisms we consider is to allocate loads placed on the agents, and an agent's secret data is the cost she incurs per unit load. We give an exact characterization for the algorithms that can be used to design truthful mechanisms for such load balancing problems using appropriate side payments. We use our characterization to design polynomial time truthful mechanisms for several problems in combinatorial optimization to which the celebrated VCG mechanism does not apply. For scheduling related parallel machines (Q/spl par/C/sub max/), we give a 3-approximation mechanism based on randomized rounding of the optimal fractional solution. This problem is NP-complete, and the standard approximation algorithms (greedy load-balancing or the PTAS) cannot be used in truthful mechanisms. We show our mechanism to be frugal, in that the total payment needed is only a logarithmic factor more than the actual costs incurred by the machines, unless one machine dominates the total processing power. We also give truthful mechanisms for maximum flow, Q/spl par//spl Sigma/C/sub j/ (scheduling related machines to minimize the sum of completion times), optimizing an affine function over a fixed set, and special cases of uncapacitated facility location. In addition, for Q/spl par//spl Sigma/w/sub j/C/sub j/ (minimizing the weighted sum of completion times), we prove a lower bound of 2//spl radic/3 for the best approximation ratio achievable by truthful mechanism.
{"title":"Truthful mechanisms for one-parameter agents","authors":"Aaron Archer, É. Tardos","doi":"10.1109/SFCS.2001.959924","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959924","url":null,"abstract":"The authors show how to design truthful (dominant strategy) mechanisms for several combinatorial problems where each agent's secret data is naturally expressed by a single positive real number. The goal of the mechanisms we consider is to allocate loads placed on the agents, and an agent's secret data is the cost she incurs per unit load. We give an exact characterization for the algorithms that can be used to design truthful mechanisms for such load balancing problems using appropriate side payments. We use our characterization to design polynomial time truthful mechanisms for several problems in combinatorial optimization to which the celebrated VCG mechanism does not apply. For scheduling related parallel machines (Q/spl par/C/sub max/), we give a 3-approximation mechanism based on randomized rounding of the optimal fractional solution. This problem is NP-complete, and the standard approximation algorithms (greedy load-balancing or the PTAS) cannot be used in truthful mechanisms. We show our mechanism to be frugal, in that the total payment needed is only a logarithmic factor more than the actual costs incurred by the machines, unless one machine dominates the total processing power. We also give truthful mechanisms for maximum flow, Q/spl par//spl Sigma/C/sub j/ (scheduling related machines to minimize the sum of completion times), optimizing an affine function over a fixed set, and special cases of uncapacitated facility location. In addition, for Q/spl par//spl Sigma/w/sub j/C/sub j/ (minimizing the weighted sum of completion times), we prove a lower bound of 2//spl radic/3 for the best approximation ratio achievable by truthful mechanism.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127454442","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}
Pub Date : 2001-10-14DOI: 10.1109/SFCS.2001.959910
Amir Shpilka
We prove lower bounds on the number of product gates in bilinear and quadratic circuits that compute the product of two n /spl times/ n matrices over finite fields. In particular we obtain the following results: 1. We show that the number of product gates in any bilinear (or quadratic) circuit that computes the product of two n /spl times/ n matrices over GF(2) is at least 3n/sup 2/ o(n/sup 2/). 2. We show that the number of product gates in any bilinear circuit that computes the product of two n /spl times/ n matrices over GF(p) is at least (2.5 + 1.5/p/sup 3/-1)n/sup 2/ - o(n/sup 2/). These results improve the former results of N.H. Bshouty (1997) and M. Blaser (1999) who proved lower bounds of 2.5n/sup 2/ o(n/sup 2/).
{"title":"Lower bounds for matrix product","authors":"Amir Shpilka","doi":"10.1109/SFCS.2001.959910","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959910","url":null,"abstract":"We prove lower bounds on the number of product gates in bilinear and quadratic circuits that compute the product of two n /spl times/ n matrices over finite fields. In particular we obtain the following results: 1. We show that the number of product gates in any bilinear (or quadratic) circuit that computes the product of two n /spl times/ n matrices over GF(2) is at least 3n/sup 2/ o(n/sup 2/). 2. We show that the number of product gates in any bilinear circuit that computes the product of two n /spl times/ n matrices over GF(p) is at least (2.5 + 1.5/p/sup 3/-1)n/sup 2/ - o(n/sup 2/). These results improve the former results of N.H. Bshouty (1997) and M. Blaser (1999) who proved lower bounds of 2.5n/sup 2/ o(n/sup 2/).","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129624616","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}
Pub Date : 2001-10-14DOI: 10.1109/SFCS.2001.959929
Frank McSherry
Problems such as bisection, graph coloring, and clique are generally believed hard in the worst case. However, they can be solved if the input data is drawn randomly from a distribution over graphs containing acceptable solutions. In this paper we show that a simple spectral algorithm can solve all three problems above in the average case, as well as a more general problem of partitioning graphs based on edge density. In nearly all cases our approach meets or exceeds previous parameters, while introducing substantial generality. We apply spectral techniques, using foremost the observation that in all of these problems, the expected adjacency matrix is a low rank matrix wherein the structure of the solution is evident.
{"title":"Spectral partitioning of random graphs","authors":"Frank McSherry","doi":"10.1109/SFCS.2001.959929","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959929","url":null,"abstract":"Problems such as bisection, graph coloring, and clique are generally believed hard in the worst case. However, they can be solved if the input data is drawn randomly from a distribution over graphs containing acceptable solutions. In this paper we show that a simple spectral algorithm can solve all three problems above in the average case, as well as a more general problem of partitioning graphs based on edge density. In nearly all cases our approach meets or exceeds previous parameters, while introducing substantial generality. We apply spectral techniques, using foremost the observation that in all of these problems, the expected adjacency matrix is a low rank matrix wherein the structure of the solution is evident.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124699040","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}
Pub Date : 2001-10-14DOI: 10.1109/SFCS.2001.959882
P. Agarwal, B. Aronov, M. Sharir
We obtain improved bounds on the complexity of m distinct faces in an arrangement of n circles and in an arrangement of n unit circles. The bounds are worst-case tight for unit circles, and, for general circles, they nearly coincide with the best known bounds for the number of incidences between m points and n circles.
{"title":"On the complexity of many faces in arrangements of circles","authors":"P. Agarwal, B. Aronov, M. Sharir","doi":"10.1109/SFCS.2001.959882","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959882","url":null,"abstract":"We obtain improved bounds on the complexity of m distinct faces in an arrangement of n circles and in an arrangement of n unit circles. The bounds are worst-case tight for unit circles, and, for general circles, they nearly coincide with the best known bounds for the number of incidences between m points and n circles.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124634304","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：