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Scheduling TimeConstrained Communication in Linear Networks
 IN PROC. 10TH ANN. ACM SYMP. ON PARALLEL ALGORITHMS AND ARCHITECTURES
, 1998
"... We study the problem of centrally scheduling multiple messages in a linear network, when each message has both a release time and a deadline. We show that the problem of transmitting optimally many messages is NPhard, both when messages may be buffered in transit and when they may not be; for eithe ..."
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Cited by 35 (1 self)
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We study the problem of centrally scheduling multiple messages in a linear network, when each message has both a release time and a deadline. We show that the problem of transmitting optimally many messages is NPhard, both when messages may be buffered in transit and when they may not be; for either case, we present efficient algorithms that produce approximately optimal schedules. In particular, our bufferless scheduling algorithm achieves throughput that is within a factor of two of optimal. We show that buffering can improve throughput in general by a logarithmic factor (but no more), but that in several significant special cases, such as when all messages can be released immediately, buffering can help by only a small constant factor. Finally, we show how to convert our centralized, offline bufferless schedules to equally productive fully...
A StateOfTheArt Review Of JobShop Scheduling Techniques
, 1998
"... A great deal of research has been focused on solving the jobshop problem (P J ), over the last forty years, resulting in a wide variety of approaches. Recently, much effort has been concentrated on hybrid methods to solve P J as a single technique cannot solve this stubborn problem. As a result muc ..."
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Cited by 32 (0 self)
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A great deal of research has been focused on solving the jobshop problem (P J ), over the last forty years, resulting in a wide variety of approaches. Recently, much effort has been concentrated on hybrid methods to solve P J as a single technique cannot solve this stubborn problem. As a result much effort has recently been concentrated on techniques that combine myopic problem specific methods and a metastrategy which guides the search out of local optima. These approaches currently provide the best results. Such hybrid techniques are known as iterated local search algorithms or metaheuristics. In this paper we seek to assess the work done in the jobshop domain by providing a review of many of the techniques used. The impact of the major contributions is indicated by applying these techniques to a set of standard benchmark problems. It is established that methods such as Tabu Search, Genetic Algorithms, Simulated Annealing should be considered complementary rather than competitive...
Task Scheduling in Networks
, 1994
"... Scheduling a set of tasks on a set of machines so as to yield an efficient schedule is a basic problem in computer science and operations research. Most of the research on this problem incorporates the potentially unrealistic assumption that communication between the different machines is instantane ..."
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Cited by 24 (6 self)
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Scheduling a set of tasks on a set of machines so as to yield an efficient schedule is a basic problem in computer science and operations research. Most of the research on this problem incorporates the potentially unrealistic assumption that communication between the different machines is instantaneous. In this paper we remove this assumption and study the problem of network scheduling, where each job originates at some node of a network, and in order to be processed at another node must take the time to travel through the network to that node. Our main contribution is to give approximation algorithms and hardness proofs for fully general forms of the fundamental problems in network scheduling. We consider two basic scheduling objectives: minimizing the makespan, and minimizing the average completion time. For the makespan we prove small constant factor hardnesstoapproximate and approximation results. For the average completion time, we give a logsquared approximation algorithm for...
An Adversarial Model for Distributed Dynamic Load Balancing
, 1998
"... We study the problem of balancing the load on processors of an arbitrary network. If jobs arrive or depart during the process of load balancing, we have the dynamic load balancing problem; otherwise, we have the static load balancing problem. While static load balancing on arbitrary and special netw ..."
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Cited by 19 (2 self)
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We study the problem of balancing the load on processors of an arbitrary network. If jobs arrive or depart during the process of load balancing, we have the dynamic load balancing problem; otherwise, we have the static load balancing problem. While static load balancing on arbitrary and special networks has been well studied, very little is known about dynamic load balancing. The difficulty lies in modeling the arrivals and departures of jobs in a clean manner. In this paper, we initiate the study of dynamic load balancing by modeling job traffic using an adversary. Our main result is that a simple, local control distributed load balancing algorithm maintains the load of the network within a stable level against this powerful adversary. Our results hold for different models of traffic patterns and processor communication. 1 Introduction An important problem in a distributed system is to balance the total workload among the various processors of the underlying system. Such load balan...
Online Algorithms for the Channel Assignment Problem in Cellular Networks
 In Proc. of the 4th ACM International Workshop on Discrete Algorithms and Methods for Mobile Computing (DIALM
, 2002
"... We consider the online channel assignment problem in the case of cellular networks and we formalize this problem as an online load balancing problem of temporary tasks with restricted assignment. For the latter problem, we provide a general solution (denoted as the cluster algorithm) and we charac ..."
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Cited by 17 (1 self)
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We consider the online channel assignment problem in the case of cellular networks and we formalize this problem as an online load balancing problem of temporary tasks with restricted assignment. For the latter problem, we provide a general solution (denoted as the cluster algorithm) and we characterize its competitive ratio in terms of the combinatorial properties of the graph representing the network. We then compare the cluster algorithm with the greedy one when applied to the channel assignment problem: It turns out that the competitive ratio of the cluster algorithm is strictly better than the competitive ratio of the greedy algorithm. The cluster method is general enough to be applied to other online load balancing problems and, for some topologies, it can be proved to be optimal.
Optimal, Distributed DecisionMaking: The Case of No Communication
 In Proceedings of the 12th International Symposium on Fundamentals of Computation Theory
, 1999
"... Abstract. We present a combinatorial framework for the study of a natural class of distributed optimization problems that involve decisionmaking by a collection of n distributed agents in the presence of incomplete information; such problems were originally considered in a load balancing setting b ..."
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Cited by 6 (2 self)
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Abstract. We present a combinatorial framework for the study of a natural class of distributed optimization problems that involve decisionmaking by a collection of n distributed agents in the presence of incomplete information; such problems were originally considered in a load balancing setting by Papadimitriou and Yannakakis (Proceedings of the 10th Annual ACM Symposium on Principles of Distributed Computing, pp. 61{64, August 1991). For any given decision protocol and assuming no communication among the agents, our framework allows to obtain a combinatorial inclusionexclusion expression for the probability that no \overflow " occurs, called the winning probability, in terms of the volume of some simple combinatorial polytope. Within our general framework, we oer a complete resolution to the special cases of oblivious algorithms, for which agents do not \look at " their inputs, and nonoblivious algorithms, for which they do, of the general optimization problem. In either case, we derive optimality conditions
Rapid Convergence of a Local Load Balancing Algorithm for Asynchronous Rings
 Theo. Comp. Sci
, 1998
"... We consider the problem of load balancing in a ring network. We present an analysis of the following local algorithm. In each step, each node of the ring examines the number of tokens at its clockwise neighbor and sends a token to the neighbor if the neighbor has fewer tokens. We show that in a s ..."
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Cited by 4 (1 self)
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We consider the problem of load balancing in a ring network. We present an analysis of the following local algorithm. In each step, each node of the ring examines the number of tokens at its clockwise neighbor and sends a token to the neighbor if the neighbor has fewer tokens. We show that in a synchronous model, for any initial token distribution b on an nnode ring, the algorithm converges to a completely balanced distribution within 4OPT(b)+n steps, where OPT(b) is the time taken by the optimal centralized algorithm to balance b completely. Our main result is an analysis of the algorithm in an asynchronous model in which local computations and messages may be arbitrarily delayed, subject to the constraint that each message is eventually delivered and each computation is eventually performed. By generalizing our analysis for the synchronous model, we show that for any initial token distribution b, the algorithm converges to a completely balanced distribution within 8OPT(b)...
Scheduling on a Ring with Unit Capacity Links
, 1994
"... We consider the problem of scheduling unitsized jobs on a ring of processors with the objective of minimizing the completion time of the last job. Unlike much previous work we place restrictions on the capacity of the network links connecting processors. We give a polynomial time centralized algori ..."
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Cited by 1 (0 self)
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We consider the problem of scheduling unitsized jobs on a ring of processors with the objective of minimizing the completion time of the last job. Unlike much previous work we place restrictions on the capacity of the network links connecting processors. We give a polynomial time centralized algorithm that produces optimal length schedules. We also give a simple distributed 2approximation algorithm. 1 Preliminaries We consider the problem of scheduling unit sized jobs on a network of processors arranged in a ring. An instance, I, of network scheduling can be described by I = (G; J) where G = (V; E) is an undirected graph representing the network and J is the set of jobs to be processed. Using the scheduling nomenclature we say there are m processors (or machines) labeled p 1 ; p 2 ; : : : pm , and n jobs. Each vertex in V corresponds to a processor and each edge corresponds to a network link (notice this means there are m nodes in the graph). Each edge has an associated capacity w...
Abstract Scheduling TimeConstrained Communication in Linear Networks
"... We study the problem of centrally scheduling multiple messages in a linear network, when each message has both a release time and a deadline. We show that the problem of transmitting optimally many messages is NPhard, both when messages may be buffered in transit and when they may not be; for eithe ..."
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We study the problem of centrally scheduling multiple messages in a linear network, when each message has both a release time and a deadline. We show that the problem of transmitting optimally many messages is NPhard, both when messages may be buffered in transit and when they may not be; for either case, we present efficient algorithms that produce approximately optimal schedules. In particular, our bufferless scheduling algorithm achieves throughput that is within a factor of two of optimal. We show that buffering can improve throughput in general by a logarithmic factor (but no more), but that in several significant special cases, such as when all messages can be released immediately, buffering can help by only a small constant factor. Finally, we show how to convert our centralized, offline bufferless schedules to equally productive fully
On Balancing Computational Load on Rings of Processors
, 1994
"... . We consider a very simple, deterministic policy for scheduling certain genres of dynamically evolving computations  specifically, computations in which tasks that spawn produce precisely two offspring  on rings of processors. Such computations include, for instance, treestructured branching ..."
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. We consider a very simple, deterministic policy for scheduling certain genres of dynamically evolving computations  specifically, computations in which tasks that spawn produce precisely two offspring  on rings of processors. Such computations include, for instance, treestructured branching computations. We believe that our policy yields good parallel speedup on most computations of the genre, but we have not yet been able to verify this. In the current paper, we show that when the evolving computations end up having the structure of complete binary trees or of twodimensional pyramidal grids, our strategy yields almost optimal parallel speedup. Specifically, a ring having p processors can execute a computation that evolves into the heightn complete binary tree (which has 2 n \Gamma 1 nodes) in time T tree (n; p) 1 p (2 n \Gamma 1) + ff n p + p; for some constant ff p ! 2 that depends only on p. Similarly, the ring can execute a computation that evolves into the si...