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67
Packet routing and jobshop scheduling in O(congestion+dilation) steps
 Combinatorica
, 1994
"... In this paper, we prove that there exists a schedule for routing any set of packets with edgesimple paths, on any network, in O(c+d) steps, where c is the congestion of the paths in the network, and d is the length of the longest path. The result has applications to packet routing in parallel machi ..."
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Cited by 119 (9 self)
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In this paper, we prove that there exists a schedule for routing any set of packets with edgesimple paths, on any network, in O(c+d) steps, where c is the congestion of the paths in the network, and d is the length of the longest path. The result has applications to packet routing in parallel machines, network emulations, and jobshop scheduling.
Adversarial Queuing Theory
, 2001
"... We consider packet routing when packets are injected continuously into a network. We develop an adversarial theory of queuing aimed at addressing some of the restrictions inherent in probabilistic analysis and queuing theory based on timeinvariant stochastic generation. We examine the stability of ..."
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Cited by 93 (0 self)
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We consider packet routing when packets are injected continuously into a network. We develop an adversarial theory of queuing aimed at addressing some of the restrictions inherent in probabilistic analysis and queuing theory based on timeinvariant stochastic generation. We examine the stability of queuing networks and policies when the arrival process is adversarial, and provide some preliminary results in this direction. Our approach sheds light on various queuing policies in simple networks, and paves the way for a systematic study of queuing with few or no probabilistic assumptions.
Approximation algorithms for disjoint paths and related routing and packing problems
 Mathematics of Operations Research
, 2000
"... Abstract. Given a network and a set of connection requests on it, we consider the maximum edgedisjoint paths and related generalizations and routing problems that arise in assigning paths for these requests. We present improved approximation algorithms and/or integrality gaps for all problems consi ..."
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Cited by 59 (1 self)
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Abstract. Given a network and a set of connection requests on it, we consider the maximum edgedisjoint paths and related generalizations and routing problems that arise in assigning paths for these requests. We present improved approximation algorithms and/or integrality gaps for all problems considered; the central theme of this work is the underlying multicommodity flow relaxation. Applications of these techniques to approximating families of packing integer programs are also presented. Key words and phrases. Disjoint paths, approximation algorithms, unsplittable flow, routing, packing, integer programming, multicommodity flow, randomized algorithms, rounding, linear programming. 1
A constantfactor approximation algorithm for packet routing, and balancing local vs. global criteria
 In Proceedings of the ACM Symposium on the Theory of Computing (STOC
, 1997
"... Abstract. We present the first constantfactor approximation algorithm for a fundamental problem: the storeandforward packet routing problem on arbitrary networks. Furthermore, the queue sizes required at the edges are bounded by an absolute constant. Thus, this algorithmbalances a global criterio ..."
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Cited by 55 (4 self)
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Abstract. We present the first constantfactor approximation algorithm for a fundamental problem: the storeandforward packet routing problem on arbitrary networks. Furthermore, the queue sizes required at the edges are bounded by an absolute constant. Thus, this algorithmbalances a global criterion (routing time) with a local criterion (maximum queue size) and shows how to get simultaneous good bounds for both. For this particular problem, approximating the routing time well, even without considering the queue sizes, was open. We then consider a class of such local vs. global problems in the context of covering integer programs and show how to improve the local criterion by a logarithmic factor by losing a constant factor in the global criterion.
Distributed Packet Switching in Arbitrary Networks
 In Proceedings of the 28th Annual ACM Symposium on Theory of Computing
, 1996
"... In a seminal paper Leighton, Maggs, and Rao consider the packet scheduling problem when a single packet has to traverse each path. They show that there exists a schedule where each packet reaches its destination in O(C + D) steps, where C is the congestion and D is the dilation. The proof relies o ..."
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Cited by 42 (2 self)
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In a seminal paper Leighton, Maggs, and Rao consider the packet scheduling problem when a single packet has to traverse each path. They show that there exists a schedule where each packet reaches its destination in O(C + D) steps, where C is the congestion and D is the dilation. The proof relies on the Lov'asz Local Lemma, and hence is not algorithmic. In a followup paper Leighton and Maggs use an algorithmic version of the Local Lemma due to Beck to give centralized algorithms for the problem. Leighton, Maggs, and Rao also give a distributed randomized algorithm where all packets reach their destinations with high probability in O(C +D log n) steps. In this paper we develop techniques to guarantee the high probability of delivering packets without resorting to the Lov'asz Local Lemma. We improve the distributed algorithm for problems with relatively high dilation to O(C) + (log n) O(log n) D + poly(log n). We extend the techniques to handle the case of infinite streams of ...
Better approximation guarantees for jobshop scheduling
 SIAM Journal on Discrete Mathematics
, 1997
"... Abstract. Jobshop scheduling is a classical NPhard problem. Shmoys, Stein, and Wein presented the first polynomialtime approximation algorithm for this problem that has a good (polylogarithmic) approximation guarantee. We improve the approximation guarantee of their work and present further impro ..."
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Cited by 32 (2 self)
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Abstract. Jobshop scheduling is a classical NPhard problem. Shmoys, Stein, and Wein presented the first polynomialtime approximation algorithm for this problem that has a good (polylogarithmic) approximation guarantee. We improve the approximation guarantee of their work and present further improvements for some important NPhard special cases of this problem (e.g., in the preemptive case where machines can suspend work on operations and later resume). We also present NC algorithms with improved approximation guarantees for some NPhard special cases.
A Packet Routing Protocol for Arbitrary Networks
 In Proceedings of the 12th Symposium on Theoretical Aspects of Computer Science
, 1995
"... . In this paper, we introduce an online protocol which routes any set of packets along shortest paths through an arbitrary Nnode network in O(congestion + diameter + log N) rounds, with high probability. This time bound is optimal up to the additive log N , and it was previously only reached for ..."
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Cited by 31 (14 self)
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. In this paper, we introduce an online protocol which routes any set of packets along shortest paths through an arbitrary Nnode network in O(congestion + diameter + log N) rounds, with high probability. This time bound is optimal up to the additive log N , and it was previously only reached for boundeddegree levelled networks. Further, we prove bounds on the congestion of random routing problems for Cayley networks and general node symmetric networks based on the construction of shortest paths systems. In particular, we give construction schemes for shortest paths systems and show that if every processor sends p packets to random destinations along the paths described in the paths system, then the congestion is bounded by O(p \Delta diameter + log N ), with high probability. Finally, we prove an (apparently suboptimal) congestion bound for random routing problems on randomly chosen regular networks. 1 Introduction Communication among the processors of a parallel computer usually ...
Path Coloring on the Mesh
 In Proc. of the 37th Annual IEEE Symposium on Foundations of Computer Science
, 1996
"... In the minimum path coloring problem, we are given a list of pairs of vertices of a graph. We are asked to connect each pair by a colored path. Paths of the same color must be edge disjoint. Our objective is to minimize the number of colors used. This problem was raised by Aggarwal et al [1] and Rag ..."
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Cited by 29 (0 self)
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In the minimum path coloring problem, we are given a list of pairs of vertices of a graph. We are asked to connect each pair by a colored path. Paths of the same color must be edge disjoint. Our objective is to minimize the number of colors used. This problem was raised by Aggarwal et al [1] and Raghavan and Upfal [22] as a model for routing in alloptical networks. It is also related to questions in circuit routing. In this paper, we improve the O(ln N ) approximation result of Kleinberg and Tardos [14] for path coloring on the N \Theta N mesh. We give an O(1) approximation algorithm to the number of colors needed, and a poly(ln ln N ) approximation algorithm to the choice of paths and colors. To the best of our knowledge, these are the first sublogarithmic bounds for any network other than trees, rings, or trees of rings. Our results are based on developing new techniques for randomized rounding. These techniques iteratively improve a fractional solution until it approaches integral...
Approximation Algorithms for Shop Scheduling Problems with Minsum Objective
, 1999
"... We consider a general class of multiprocessor shop scheduling problems, preemptive or nonpreemptive, with precedence constraints between operations, with job or operation release dates, andwith aclassofobjectivefunctions including weightedsums ofjob, operations and stage completion times. We present ..."
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Cited by 24 (6 self)
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We consider a general class of multiprocessor shop scheduling problems, preemptive or nonpreemptive, with precedence constraints between operations, with job or operation release dates, andwith aclassofobjectivefunctions including weightedsums ofjob, operations and stage completion times. We present a general approximation method combining a linear programming relaxation in the operation completion times, with any algorithm for the makespan version of these problems without release dates. If the latter produces a schedule with makespan no larger than ρ times the “trivial lower bound” consisting of the largest of all stage average loads (or “congestion”) and job lengths (or “dilation”), then our method produces a feasible schedule with minsum objective no larger than 2eρ times the optimum where 2e ≈ 5.44. This leads in particular to a polynomial time algorithm with polylogarithmic performance guarantee for the minsum multiprocessor dagshop problem J(P)rij,dag j  ∑ S wSCS where ∑ S wSCS is a general minsum objective including weighted sum of operation and job completion times, stages makespans and others, whereas the best known earlier performance guarantees were O(m) (where m is the number of stages) for the special cases J  ∑ Cj (Gonzalez and Sahni, 1978), F(P)rj  ∑ wjCj (Schulz, 1996) and O  ∑ Cj (Achugbue and Chin, 1982). We also obtain a O(1) performance guarantee for the acyclic job shop problem Jpij = 1,acyclic−dagj  ∑ S wSCS with unit processing times and weighted sum of operation (or job) completion time objective. Our results extend to a broad class of minsum objective functions including some convex objectives related to load balancing. We then present an improved 5.83approximation algorithm for the open shop problem Orj  ∑ wjCj with total weighted job completion time objective. We conclude with a very simple method which yields O(m)approximation algorithms for various job shop problems (preemptive, nonpreemptive, and nowait) with m singleprocessor stages and total weighted job completion time objective.
Approximation Algorithms Via Randomized Rounding: A Survey
 Series in Advanced Topics in Mathematics, Polish Scientific Publishers PWN
, 1999
"... Approximation algorithms provide a natural way to approach computationally hard problems. There are currently many known paradigms in this area, including greedy algorithms, primaldual methods, methods based on mathematical programming (linear and semidefinite programming in particular), local i ..."
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Approximation algorithms provide a natural way to approach computationally hard problems. There are currently many known paradigms in this area, including greedy algorithms, primaldual methods, methods based on mathematical programming (linear and semidefinite programming in particular), local improvement, and "low distortion" embeddings of general metric spaces into special families of metric spaces. Randomization is a useful ingredient in many of these approaches, and particularly so in the form of randomized rounding of a suitable relaxation of a given problem. We survey this technique here, with a focus on correlation inequalities and their applications.