Pub Date : 2001-10-14DOI: 10.1109/SFCS.2001.959928
Stavros G. Kolliopoulos, N. Young
In this paper we study approximation algorithms for solving a general covering integer program. An n-vector x of nonnegative integers is sought, which minimizes c/sup T//spl middot/x, subject to Ax/spl ges/b, x/spl les/d. The entries of A, b, c are nonnegative. Let m be the number of rows of A. Covering problems have been heavily studied in combinatorial optimization. We focus on the effect of the multiplicity constraints, x/spl les/d, on approximately. Two longstanding open questions remain for this general formulation with upper bounds on the variables. (i) The integrality gap of the standard LP relaxation is arbitrarily large. Existing approximation algorithms that achieve the well-known O(log m)-approximation with respect to the LP value do so at the expense of violating the upper bounds on the variables by the same O(log m) multiplicative factor. What is the smallest possible violation of the upper bounds that still achieves cost within O(log m) of the standard LP optimum? (ii) The best known approximation ratio for the problem has been O(log(max/sub j//spl Sigma//sub i/A/sub ij/)) since 1982. This bound can be as bad as polynomial in the input size. Is an O(log m)-approximation, like the one known for the special case of Set Cover, possible? We settle these two open questions. To answer the first question we give an algorithm based on the relatively simple new idea of randomly rounding variables to smaller-than-integer units. To settle the second question we give a reduction from approximating the problem while respecting multiplicity constraints to approximating the problem with a bounded violation of the multiplicity constraints.
{"title":"Tight approximation results for general covering integer programs","authors":"Stavros G. Kolliopoulos, N. Young","doi":"10.1109/SFCS.2001.959928","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959928","url":null,"abstract":"In this paper we study approximation algorithms for solving a general covering integer program. An n-vector x of nonnegative integers is sought, which minimizes c/sup T//spl middot/x, subject to Ax/spl ges/b, x/spl les/d. The entries of A, b, c are nonnegative. Let m be the number of rows of A. Covering problems have been heavily studied in combinatorial optimization. We focus on the effect of the multiplicity constraints, x/spl les/d, on approximately. Two longstanding open questions remain for this general formulation with upper bounds on the variables. (i) The integrality gap of the standard LP relaxation is arbitrarily large. Existing approximation algorithms that achieve the well-known O(log m)-approximation with respect to the LP value do so at the expense of violating the upper bounds on the variables by the same O(log m) multiplicative factor. What is the smallest possible violation of the upper bounds that still achieves cost within O(log m) of the standard LP optimum? (ii) The best known approximation ratio for the problem has been O(log(max/sub j//spl Sigma//sub i/A/sub ij/)) since 1982. This bound can be as bad as polynomial in the input size. Is an O(log m)-approximation, like the one known for the special case of Set Cover, possible? We settle these two open questions. To answer the first question we give an algorithm based on the relatively simple new idea of randomly rounding variables to smaller-than-integer units. To settle the second question we give a reduction from approximating the problem while respecting multiplicity constraints to approximating the problem with a bounded violation of the multiplicity constraints.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"29 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":"131843269","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.2001.959888
R. Canetti
We propose a novel paradigm for defining security of cryptographic protocols, called universally composable security. The salient property of universally composable definitions of security is that they guarantee security even when a secure protocol is composed of an arbitrary set of protocols, or more generally when the protocol is used as a component of an arbitrary system. This is an essential property for maintaining security of cryptographic protocols in complex and unpredictable environments such as the Internet. In particular, universally composable definitions guarantee security even when an unbounded number of protocol instances are executed concurrently in an adversarially controlled manner, they guarantee non-malleability with respect to arbitrary protocols, and more. We show how to formulate universally composable definitions of security for practically any cryptographic task. Furthermore, we demonstrate that practically any such definition can be realized using known techniques, as long as only a minority of the participants are corrupted. We then proceed to formulate universally composable definitions of a wide array of cryptographic tasks, including authenticated and secure communication, key-exchange, public-key encryption, signature, commitment, oblivious transfer, zero knowledge and more. We also make initial steps towards studying the realizability of the proposed definitions in various settings.
{"title":"Universally composable security: a new paradigm for cryptographic protocols","authors":"R. Canetti","doi":"10.1109/SFCS.2001.959888","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959888","url":null,"abstract":"We propose a novel paradigm for defining security of cryptographic protocols, called universally composable security. The salient property of universally composable definitions of security is that they guarantee security even when a secure protocol is composed of an arbitrary set of protocols, or more generally when the protocol is used as a component of an arbitrary system. This is an essential property for maintaining security of cryptographic protocols in complex and unpredictable environments such as the Internet. In particular, universally composable definitions guarantee security even when an unbounded number of protocol instances are executed concurrently in an adversarially controlled manner, they guarantee non-malleability with respect to arbitrary protocols, and more. We show how to formulate universally composable definitions of security for practically any cryptographic task. Furthermore, we demonstrate that practically any such definition can be realized using known techniques, as long as only a minority of the participants are corrupted. We then proceed to formulate universally composable definitions of a wide array of cryptographic tasks, including authenticated and secure communication, key-exchange, public-key encryption, signature, commitment, oblivious transfer, zero knowledge and more. We also make initial steps towards studying the realizability of the proposed definitions in various settings.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"112 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":"127617639","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.2001.959895
Michael Alekhnovich, A. Razborov
We show that neither Resolution nor tree-like Resolution is automatizable unless the class W[P] from the hierarchy of parameterized problems is fixed-parameter tractable by randomized algorithms with one-sided error.
{"title":"Resolution is not automatizable unless W[P] is tractable","authors":"Michael Alekhnovich, A. Razborov","doi":"10.1109/SFCS.2001.959895","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959895","url":null,"abstract":"We show that neither Resolution nor tree-like Resolution is automatizable unless the class W[P] from the hierarchy of parameterized problems is fixed-parameter tractable by randomized algorithms with one-sided error.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"63 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":"124481639","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.2001.959937
J. Håstad, Subhash Khot
For every integer k>1, we present a PCP characterization of NP where the verifier uses logarithmic randomness, queries 4k+k/sup 2/ bits in the proof, accepts a correct proof with probability 1 (i.e. it is has perfect completeness) and accepts any supposed proof of a false statement with a certain maximum probability. In particular, the verifier achieves optimal amortized query complexity of 1+/spl delta/ for arbitrarily small constant /spl delta/>0. Such a characterization was already proved by A. Samorodnitsky and L. Trevisan (2000), but their verifier loses perfect completeness and their proof makes an essential use of this feature. By using an adaptive verifier, we can decrease the number of query bits to 2k+k/sup 2/, the same number obtained by Samorodnitsky and Trevisan. Finally, we extend some of the results to larger domains.
{"title":"Query efficient PCPs with perfect completeness","authors":"J. Håstad, Subhash Khot","doi":"10.1109/SFCS.2001.959937","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959937","url":null,"abstract":"For every integer k>1, we present a PCP characterization of NP where the verifier uses logarithmic randomness, queries 4k+k/sup 2/ bits in the proof, accepts a correct proof with probability 1 (i.e. it is has perfect completeness) and accepts any supposed proof of a false statement with a certain maximum probability. In particular, the verifier achieves optimal amortized query complexity of 1+/spl delta/ for arbitrarily small constant /spl delta/>0. Such a characterization was already proved by A. Samorodnitsky and L. Trevisan (2000), but their verifier loses perfect completeness and their proof makes an essential use of this feature. By using an adaptive verifier, we can decrease the number of query bits to 2k+k/sup 2/, the same number obtained by Samorodnitsky and Trevisan. Finally, we extend some of the results to larger domains.","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":"122544288","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.2001.959907
Martin Pál, É. Tardos, T. Wexler
The authors give the first constant factor approximation algorithm for the facility location problem with nonuniform, hard capacities. Facility location problems have received a great deal of attention in recent years. Approximation algorithms have been developed for many variants. Most of these algorithms are based on linear programming, but the LP techniques developed thus far have been unsuccessful in dealing with hard capacities. A local-search based approximation algorithm (M. Korupolu et al., 1998; F.A. Chudak and D.P. Williamson, 1999) is known for the special case of hard but uniform capacities. We present a local-search heuristic that yields an approximation guarantee of 9 + /spl epsi/ for the case of nonuniform hard capacities. To obtain this result, we introduce new operations that are natural in this context. Our proof is based on network flow techniques.
针对具有非均匀硬容量的设施选址问题，给出了第一种常因子近似算法。近年来，设施选址问题受到了广泛的关注。已经为许多变体开发了近似算法。这些算法大多基于线性规划，但迄今为止开发的LP技术在处理硬容量方面并不成功。基于局部搜索的近似算法(M. Korupolu et al.， 1998;F.A. Chudak和D.P. Williamson(1999)以硬但统一的能力的特殊情况而闻名。我们提出了一个局部搜索启发式算法，对于非均匀硬容量的情况，它产生了9 + /spl epsi/的近似保证。为了获得这个结果，我们引入了在这个上下文中很自然的新操作。我们的证明是基于网络流技术。
{"title":"Facility location with nonuniform hard capacities","authors":"Martin Pál, É. Tardos, T. Wexler","doi":"10.1109/SFCS.2001.959907","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959907","url":null,"abstract":"The authors give the first constant factor approximation algorithm for the facility location problem with nonuniform, hard capacities. Facility location problems have received a great deal of attention in recent years. Approximation algorithms have been developed for many variants. Most of these algorithms are based on linear programming, but the LP techniques developed thus far have been unsuccessful in dealing with hard capacities. A local-search based approximation algorithm (M. Korupolu et al., 1998; F.A. Chudak and D.P. Williamson, 1999) is known for the special case of hard but uniform capacities. We present a local-search heuristic that yields an approximation guarantee of 9 + /spl epsi/ for the case of nonuniform hard capacities. To obtain this result, we introduce new operations that are natural in this context. Our proof is based on network flow techniques.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"45 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":"129087045","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.2001.959915
A. Meyerson, Kamesh Munagala, Serge A. Plotkin
We consider the problem of incrementally designing a network to route demand to a single sink on an underlying metric space. We are given cables whose costs per unit length scale in a concave fashion with capacity. Under certain natural restrictions on the costs (called the Access Network Design constraints), we present a simple and efficient randomized algorithm that is competitive to the minimum cost solution when the demand points arrive online. In particular, if the order of arrival is a random permutation, we can prove a O(1) competitive ratio. For the fully adversarial case, the algorithm is O(K) -competitive, where K is the number of different pipe types. Since the value of K is typically small, this improves the previous O(log n log log n)-competitive algorithm which was based on probabilistically approximating the underlying metric by a tree metric. Our algorithm also improves the best known approximation ratio and running time for the offline version of this problem.
我们考虑增量设计网络的问题，将需求路由到底层度量空间上的单个接收器。给定电缆，其单位长度的成本与容量呈凹形关系。在一定的自然成本限制下(称为接入网设计约束)，我们提出了一个简单有效的随机算法，当需求点到达在线时，该算法与最小成本解决方案竞争。特别是，如果到达顺序是随机排列，我们可以证明一个O(1)竞争比。对于完全对抗的情况，算法是O(K)竞争的，其中K是不同管道类型的数量。由于K的值通常很小，这改进了之前的O(log n log log n)竞争算法，该算法基于通过树度量概率近似底层度量。我们的算法还改进了该问题的离线版本的最著名的近似比和运行时间。
{"title":"Designing networks incrementally","authors":"A. Meyerson, Kamesh Munagala, Serge A. Plotkin","doi":"10.1109/SFCS.2001.959915","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959915","url":null,"abstract":"We consider the problem of incrementally designing a network to route demand to a single sink on an underlying metric space. We are given cables whose costs per unit length scale in a concave fashion with capacity. Under certain natural restrictions on the costs (called the Access Network Design constraints), we present a simple and efficient randomized algorithm that is competitive to the minimum cost solution when the demand points arrive online. In particular, if the order of arrival is a random permutation, we can prove a O(1) competitive ratio. For the fully adversarial case, the algorithm is O(K) -competitive, where K is the number of different pipe types. Since the value of K is typically small, this improves the previous O(log n log log n)-competitive algorithm which was based on probabilistically approximating the underlying metric by a tree metric. Our algorithm also improves the best known approximation ratio and running time for the offline version of this problem.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"176 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":"122784757","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.2001.959891
M. Andrews, Antonio Fernández, Ashish Goel, Lisa Zhang
We study routing and scheduling in packet-switched networks. We assume an adversary that controls the injection time, source, and destination for each packet injected. A set of paths for these packets is admissible if no link in the network is overloaded. We present the first on-line routing algorithm that finds a set of admissible paths whenever this is feasible. Our algorithm calculates a path for each packet as soon as it is injected at its source using a simple shortest path computation. The length of a link reflects its current congestion. We also show how our algorithm can be implemented under today's Internet routing paradigms. When the paths are known (either given by the adversary or computed as above) our goal is to schedule the packets along the given paths so that the packets experience small end-to-end delays. The best previous delay bounds for deterministic and distributed scheduling protocols were exponential in the path length. In this paper we present the first deterministic and distributed scheduling protocol that guarantees a polynomial end-to-end delay for every packet. Finally, we discuss the effects of combining routing with scheduling. We first show that some, unstable scheduling protocols remain unstable no matter how the paths are chosen. However, the freedom to choose paths can make a difference. For example, we show that a ring with parallel links is stable for all greedy scheduling protocols if paths are chosen intelligently, whereas this is not the case if the adversary specifies the paths.
{"title":"Source routing and scheduling in packet networks","authors":"M. Andrews, Antonio Fernández, Ashish Goel, Lisa Zhang","doi":"10.1109/SFCS.2001.959891","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959891","url":null,"abstract":"We study routing and scheduling in packet-switched networks. We assume an adversary that controls the injection time, source, and destination for each packet injected. A set of paths for these packets is admissible if no link in the network is overloaded. We present the first on-line routing algorithm that finds a set of admissible paths whenever this is feasible. Our algorithm calculates a path for each packet as soon as it is injected at its source using a simple shortest path computation. The length of a link reflects its current congestion. We also show how our algorithm can be implemented under today's Internet routing paradigms. When the paths are known (either given by the adversary or computed as above) our goal is to schedule the packets along the given paths so that the packets experience small end-to-end delays. The best previous delay bounds for deterministic and distributed scheduling protocols were exponential in the path length. In this paper we present the first deterministic and distributed scheduling protocol that guarantees a polynomial end-to-end delay for every packet. Finally, we discuss the effects of combining routing with scheduling. We first show that some, unstable scheduling protocols remain unstable no matter how the paths are chosen. However, the freedom to choose paths can make a difference. For example, we show that a ring with parallel links is stable for all greedy scheduling protocols if paths are chosen intelligently, whereas this is not the case if the adversary specifies the paths.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"2017 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":"128039410","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.2001.959893
Michael Alekhnovich, A. Razborov
We generalize recent linear lower bounds for Polynomial Calculus based on binomial ideals. We produce a general hardness criterion (that we call immunity) which is satisfied by a random function and prove linear lower bounds on the degree of PC refutations for a wide class of tautologies based on immune functions. As some applications of our techniques, we introduce mod/sub p/ Tseitin tautologies in the Boolean case (e.g. in the presence of axioms x/sub i//sup 2/=x/sub i/), prove that they are hard for PC over fields with characteristic different from p, and generalize them to Flow tautologies which are based on the MAJORITY function and are proved to be hard over any field. We also show the /spl Omega/(n) lower bound for random k-CNFs over fields of characteristic 2.
{"title":"Lower bounds for polynomial calculus: non-binomial case","authors":"Michael Alekhnovich, A. Razborov","doi":"10.1109/SFCS.2001.959893","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959893","url":null,"abstract":"We generalize recent linear lower bounds for Polynomial Calculus based on binomial ideals. We produce a general hardness criterion (that we call immunity) which is satisfied by a random function and prove linear lower bounds on the degree of PC refutations for a wide class of tautologies based on immune functions. As some applications of our techniques, we introduce mod/sub p/ Tseitin tautologies in the Boolean case (e.g. in the presence of axioms x/sub i//sup 2/=x/sub i/), prove that they are hard for PC over fields with characteristic different from p, and generalize them to Flow tautologies which are based on the MAJORITY function and are proved to be hard over any field. We also show the /spl Omega/(n) lower bound for random k-CNFs over fields of characteristic 2.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"76 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":"128072113","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.2001.959884
Sariel Har-Peled
For a set P of n points in R/sup d/, we define a new type of space decomposition. The new diagram provides an /spl epsi/-approximation to the distance function associated with the Voronoi diagram of P, while being of near linear size, for d/spl ges/2. This contrasts with the standard Voronoi diagram that has /spl Omega/ (n/sup [d/2]/) complexity in the worst case.
{"title":"A replacement for Voronoi diagrams of near linear size","authors":"Sariel Har-Peled","doi":"10.1109/SFCS.2001.959884","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959884","url":null,"abstract":"For a set P of n points in R/sup d/, we define a new type of space decomposition. The new diagram provides an /spl epsi/-approximation to the distance function associated with the Voronoi diagram of P, while being of near linear size, for d/spl ges/2. This contrasts with the standard Voronoi diagram that has /spl Omega/ (n/sup [d/2]/) complexity in the worst case.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"70 9-10","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114014048","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.2001.959916
Anupam Gupta, Amit Kumar
The study of the effect of priced information on basic algorithmic problems was initiated by M. Charikar et al. (2000). The authors continue the study of sorting and selection in the priced comparison model, i.e., when each comparison has an associated cost, and answer some of the open problems suggested by Charikar et al. If the comparison costs are allowed to be arbitrary, we show that one cannot get good approximation ratios. A different way to assign costs is based on the idea that one can distill out an intrinsic value for each item being compared, such that the cost of comparing two elements is some "well-behaved" or "structured" function of their values. We feel that most practical applications will have some structured cost property. The authors study the problems of sorting and selection (which includes finding the maximum and the median) in the structured cost model. We get a variety of approximation results for these problems, depending on the restrictions we put on the structured costs. We show that it is possible to get much improved results with the structured cost model than the case when we do not have any assumptions on comparison costs.
{"title":"Sorting and selection with structured costs","authors":"Anupam Gupta, Amit Kumar","doi":"10.1109/SFCS.2001.959916","DOIUrl":"https://doi.org/10.1109/SFCS.2001.959916","url":null,"abstract":"The study of the effect of priced information on basic algorithmic problems was initiated by M. Charikar et al. (2000). The authors continue the study of sorting and selection in the priced comparison model, i.e., when each comparison has an associated cost, and answer some of the open problems suggested by Charikar et al. If the comparison costs are allowed to be arbitrary, we show that one cannot get good approximation ratios. A different way to assign costs is based on the idea that one can distill out an intrinsic value for each item being compared, such that the cost of comparing two elements is some \"well-behaved\" or \"structured\" function of their values. We feel that most practical applications will have some structured cost property. The authors study the problems of sorting and selection (which includes finding the maximum and the median) in the structured cost model. We get a variety of approximation results for these problems, depending on the restrictions we put on the structured costs. We show that it is possible to get much improved results with the structured cost model than the case when we do not have any assumptions on comparison costs.","PeriodicalId":378126,"journal":{"name":"Proceedings 2001 IEEE International Conference on Cluster Computing","volume":"18 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":"131878410","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}
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