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53
Flow and Stretch Metrics for Scheduling Continuous Job Streams
 In Proceedings of the 9th Annual ACMSIAM Symposium on Discrete Algorithms
, 1998
"... this paper, we isolate and study the problem of scheduling a continuous stream of requests of varying sizes. More precisely, assume a request or job j has ..."
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Cited by 126 (9 self)
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this paper, we isolate and study the problem of scheduling a continuous stream of requests of varying sizes. More precisely, assume a request or job j has
Connection Scheduling in Web Servers
 IN USENIX SYMPOSIUM ON INTERNET TECHNOLOGIES AND SYSTEMS
, 1999
"... Under high loads, a Web server may be servicing manyhundreds of connections concurrently. In traditional ..."
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Cited by 107 (7 self)
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Under high loads, a Web server may be servicing manyhundreds of connections concurrently. In traditional
A constantfactor approximation algorithm for the multicommodity rentorbuy problem
 In Proceedings of the 43rd Annual IEEE Symposium on Foundations of Computer Science
, 2002
"... We present the first constantfactor approximation algorithm for network design with multiple commodities and economies of scale. We consider the rentorbuy problem, a type of multicommodity buyatbulk network design in which there are two ways to install capacity on any given edge. Capacity can b ..."
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Cited by 83 (9 self)
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We present the first constantfactor approximation algorithm for network design with multiple commodities and economies of scale. We consider the rentorbuy problem, a type of multicommodity buyatbulk network design in which there are two ways to install capacity on any given edge. Capacity can be rented, with cost incurred on a perunit of capacity basis, or bought, which allows unlimited use after payment of a large fixed cost. Given a graph and a set of sourcesink pairs, we seek a minimumcost way of installing sufficient capacity on edges so that a prescribed amount of flow can be sent simultaneously from each source to the corresponding sink. Recent work on buyatbulk network design has concentrated on the special case where all sinks are identical; existing constantfactor approximation algorithms for this special case make crucial use of the assumption that all commodities ship flow to the same sink vertex and do not obviously extend to the multicommodity rentorbuy problem. Prior to our work, the best heuristics for the multicommodity rentorbuy problem achieved only logarithmic performance guarantees and relied on the machinery of relaxed metrical task systems or of metric embeddings. By contrast, we solve the network design problem directly via a novel primaldual algorithm. 1
Asymptotically optimal algorithm for job shop scheduling and packet routing
 J. Algorithms
, 1999
"... We propose asymptotically optimal algorithms for the job shop scheduling and packet routing problems. We propose a fluid relaxation for the job shop scheduling problem in which we replace discrete jobs with the flow of a continuous fluid. We compute an optimal solution of the fluid relaxation in clo ..."
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Cited by 51 (3 self)
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We propose asymptotically optimal algorithms for the job shop scheduling and packet routing problems. We propose a fluid relaxation for the job shop scheduling problem in which we replace discrete jobs with the flow of a continuous fluid. We compute an optimal solution of the fluid relaxation in closed form, obtain a lower bound Cmax to the job shop scheduling problem, and construct a feasible schedule from the fluid relaxation with objective value at most C � OŽ C. max ' max, where the constant in the OŽ. � notation is independent of the number of jobs, but it depends on the processing time of the jobs, thus producing an asymptotically optimal schedule as the total number of jobs tends to infinity. If the initially present jobs increase proportionally, then our algorithm produces a schedule with value at most C � OŽ. max 1. For the packet routing problem with fixed paths the previous algorithm applies directly. For the general packet routing problem we propose a linear programming relaxation that provides a lower bound Cmax and an asymptotically optimal algorithm that uses the optimal solution of the relaxation with objective value at most C � OŽ C. max ' max. Unlike asymptotically optimal algorithms that rely on probabilistic assumptions, our proposed algorithms make no probabilistic assumptions and they are asymptotically optimal for all instances with a large number of jobs Ž packets.. In computational experiments our algorithms produce schedules which are within 1 % of optimality even for moderately sized problems.
PATHS: Analysis of PATH Duration Statistics and their Impact on Reactive MANET Routing Protocols
 in Proc. of MobiHoc
, 2003
"... We develop a detailed approach to study how mobility impacts the performance of reactive MANET routing protocols. In particular we examine how the statistics of path durations including PDFs vary with the parameters such as the mobility model, relative speed, number of hops, and radio range. We find ..."
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Cited by 50 (4 self)
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We develop a detailed approach to study how mobility impacts the performance of reactive MANET routing protocols. In particular we examine how the statistics of path durations including PDFs vary with the parameters such as the mobility model, relative speed, number of hops, and radio range. We find that at low speeds, certain mobility models may induce multimodal distributions that reflect the characteristics of the spatial map, mobility constraints and the communicating tra#c pattern. However, our study suggests that at moderate and high velocities the exponential distribution with appropriate parameterizations is a good approximation of the path duration distribution for a range of mobility models. The reciprocal of the average path duration is analytically shown to have a strong linear relationship with the throughput and overhead that is confirmed by the simulation results for DSR.
Operator Scheduling in Data Stream Systems
 THE VLDB JOURNAL
, 2003
"... In many applications involving continuous data streams, data arrival is bursty and data rate fluctuates over time. Systems that seek to give rapid or realtime query responses in such an environment must be prepared to deal gracefully with bursts in data arrival without compromising system performan ..."
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Cited by 33 (1 self)
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In many applications involving continuous data streams, data arrival is bursty and data rate fluctuates over time. Systems that seek to give rapid or realtime query responses in such an environment must be prepared to deal gracefully with bursts in data arrival without compromising system performance. We discuss one strategy for processing bursty streams  adaptive, loadaware scheduling of query operators to minimize resource consumption during times of peak load. We show that the choice of an operator scheduling strategy can have significant impact on the runtime system memory usage as well as output latency. Our aim is to design a scheduling strategy that minimizes the maximum runtime system memory, while maintaining the output latency within prespecified bounds. We first present Chain scheduling, an operator scheduling strategy for data stream systems that is nearoptimal in minimizing runtime memory usage for any collection of singlestream queries involving selections, projections, and foreignkey joins with stored relations. Chain scheduling also performs well for queries with slidingwindow joins over multiple streams, and multiple queries of the above types. However, during bursts in input streams, when there is a buildup of unprocessed tuples, Chain scheduling may lead to high output latency. We study the online problem of minimizing maximum runtime memory, subject to a constraint on maximum latency. We present preliminary observations, negative results, and heuristics for this problem. A thorough
Great expectations: The value of spatial diversity in wireless networks
 PROCEEDINGS OF THE IEEE
, 2004
"... In this paper, the effect of spatial diversity on the throughput and reliability of wireless networks is examined. Spatial diversity is realized through multiple independently fading transmit/receive antenna paths in singleuser communication and through independently fading links in multiuser commu ..."
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Cited by 28 (7 self)
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In this paper, the effect of spatial diversity on the throughput and reliability of wireless networks is examined. Spatial diversity is realized through multiple independently fading transmit/receive antenna paths in singleuser communication and through independently fading links in multiuser communication. Adopting spatial diversity as a central theme, we start by studying its informationtheoretic foundations, then we illustrate its benefits across the physical (signal transmission/coding and receiver signal processing) and networking (resource allocation, routing, and applications) layers. Throughout the paper, we discuss engineering intuition and tradeoffs, emphasizing the strong interactions between the various network functionalities.
Backfilling with Lookahead to Optimize the Performance of Parallel Job Scheduling
"... The utilization of parallel computers depends on how jobs are packed together: if the jobs are not packed tightly, resources are lost due to fragmentation. ..."
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Cited by 23 (2 self)
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The utilization of parallel computers depends on how jobs are packed together: if the jobs are not packed tightly, resources are lost due to fragmentation.
A Comparative Study of Online Scheduling Algorithms for Networks of Workstations
"... Networks of workstations offer large amounts of unused processing time. Resource management systems are able to exploit this computing capacity by assigning computeintensive tasks to idle workstations. To avoid interferences between multiple, concurrently running applications, such resource mana ..."
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Cited by 17 (1 self)
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Networks of workstations offer large amounts of unused processing time. Resource management systems are able to exploit this computing capacity by assigning computeintensive tasks to idle workstations. To avoid interferences between multiple, concurrently running applications, such resource management systems have to schedule application jobs carefully. Continuously arriving jobs and dynamically changing amounts of available CPU capacity make traditional scheduling algorithms difficult to apply in workstation networks. Online scheduling algorithms promise better results by adapting schedules to changing situations. This paper compares six online scheduling algorithms by simulating several workload scenarios. Based on the insights gained by the simulations, the three online scheduling algorithms performing best were implemented in the Winner resource management system. Experiments conducted with Winner in a real workstation network confirm the simulation results obtained.
The Case for SRPT Scheduling in Web Servers
, 1998
"... The ShortestRemainingProcessingTime (SRPT) scheduling policy is known to be the optimal policy for minimizing mean response time, but it is rarely employed in computing systems for a number of reasons. These reasons include: lack of knowledge of task size, fear of starvation of the large tasks ..."
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Cited by 16 (5 self)
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The ShortestRemainingProcessingTime (SRPT) scheduling policy is known to be the optimal policy for minimizing mean response time, but it is rarely employed in computing systems for a number of reasons. These reasons include: lack of knowledge of task size, fear of starvation of the large tasks, concern over preemption overhead, and lack of empirical evidence on the performance benefits of switching to SRPT. In this paper we argue that the special characteristics of Web servers and Web workloads make the usual objections to SRPT less persuasive. We start by