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Implications of Classical Scheduling Results For RealTime Systems
 IEEE COMPUTER
, 1995
"... Important classical scheduling theory results for realtime computing are identified. Implications of these results from the perspective of a realtime systems designer are discussed. Uniprocessor and multiprocessor results are addressed as well as important issues such as future release times, pre ..."
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Cited by 121 (1 self)
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Important classical scheduling theory results for realtime computing are identified. Implications of these results from the perspective of a realtime systems designer are discussed. Uniprocessor and multiprocessor results are addressed as well as important issues such as future release times, precedence constraints, shared resources, task value, overloads, static versus dynamic scheduling, preemption versus nonpreemption, multiprocessing anomalies, and metrics. Examples of what scheduling algorithms are used in actual applications are given.
Scheduling Dependent RealTime Activities
, 1990
"... A realtime application is typically composed of a number of cooperating activities that must execute within specific time intervals. Since there are usually more activities to be executed than there are processors on which to execute them, several activities must share a single processor. Necessari ..."
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Cited by 74 (1 self)
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A realtime application is typically composed of a number of cooperating activities that must execute within specific time intervals. Since there are usually more activities to be executed than there are processors on which to execute them, several activities must share a single processor. Necessarily, satisfying the activities' timing constraints is a prime concern in making the scheduling decisions for that processor.
Scheduling Algorithms
, 1997
"... Introduction Scheduling theory is concerned with the optimal allocation of scarce resources to activities over time. The practice of this field dates to the first time two humans contended for a shared resource and developed a plan to share it without bloodshed. The theory of the design of algorith ..."
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Cited by 63 (1 self)
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Introduction Scheduling theory is concerned with the optimal allocation of scarce resources to activities over time. The practice of this field dates to the first time two humans contended for a shared resource and developed a plan to share it without bloodshed. The theory of the design of algorithms for scheduling is younger, but still has a significant historythe earliest papers in the field were published more than forty years ago. Scheduling problems arise in a variety of settings, as is illustrated by the following examples: Example 1: Consider the central processing unit of a computer that must process a sequence of jobs that arrive over time. In what order should the jobs be processed in order to minimize, on average, the time that a job is in the system from arrival to completion? Example 2: Consider a team of five astronauts preparing for the reentry of their space shuttle into the at
On Maintaining Priorities in a Production Rule System
 In Proceedings of the Seventeenth International Conference on Very Large Data Bases
, 1991
"... We present a priority system which is particularly suited for production rules coupled to databases. In this system, there are default priorities between all rules and overriding userdefined priorities between particular rules. Rule processing using this system is repeatable: for a given set of rul ..."
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Cited by 31 (2 self)
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We present a priority system which is particularly suited for production rules coupled to databases. In this system, there are default priorities between all rules and overriding userdefined priorities between particular rules. Rule processing using this system is repeatable: for a given set of rules and priorities, the rules are considered for execution in the same order if the same set of transactions is executed twice on the same initial database state. The rule order adheres to the default order as closely as possible: rules are considered in the same order as the default order unless userdefined precedence constraints force an inversion. We present data structures and efficient algorithms for implementing such a priority system. We show how the data structures can be incrementally maintained as userdefined priorities are altered. We also discuss how the proposed scheme can be extended to build a multilevel hierarchical priority system. 1 Introduction Incorporation of producti...
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 21 (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...
A Parametrized BranchandBound Strategy for Scheduling PrecedenceConstrained Tasks on a Multiprocessor System
 Proc. of the Int'l Conf. on Parallel Processing
, 1997
"... In this paper we experimentally evaluate the performance of a parametrized branchandbound (B&B) algorithm for scheduling realtime tasks on a multiprocessor system. The objective of the B&B algorithm is to minimize the maximum task lateness in the system. We show that a lastinfirstout (LIFO) ve ..."
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Cited by 20 (7 self)
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In this paper we experimentally evaluate the performance of a parametrized branchandbound (B&B) algorithm for scheduling realtime tasks on a multiprocessor system. The objective of the B&B algorithm is to minimize the maximum task lateness in the system. We show that a lastinfirstout (LIFO) vertex selection rule clearly outperforms the commonly used leastlowerbound (LLB) rule for the scheduling problem. We also present a new adaptive lowerbound cost function that greatly improves the performance of the B&B algorithm when parallelism in the application cannot be fully exploited on the multiprocessor architecture. Finally, we evaluate a set of heuristic strategies, one of which generates nearoptimal results with performance guarantees and another of which generates approximate results without performance guarantees. 1 Introduction Since its introduction in the field of artificial intelligence, the branchandbound (B&B) strategy has been successfully used for finding optimal ...
Synthesis of Hard RealTime Application Specific Systems
, 1998
"... This paper presents a system level approach for the synthesis of hard realtime multitask application specific systems. The algorithm takes into account task precedence constraints among multiple hard realtime tasks and targets a multiprocessor system consisting of a set of heterogeneous offthesh ..."
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Cited by 19 (2 self)
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This paper presents a system level approach for the synthesis of hard realtime multitask application specific systems. The algorithm takes into account task precedence constraints among multiple hard realtime tasks and targets a multiprocessor system consisting of a set of heterogeneous offtheshelf processors. The optimization goal is to select a minimal cost multisubset of processors while satisfying all the required timing and precedence constraints. There are three design phases: resource allocation, assignment, and scheduling. Since the resource allocation is a search for a minimal cost multisubset of processors, we adopted an A* search based technique for the first synthesis phase. A variation of the forcedirected optimization technique is used to assign a task to an allocated processor. The final scheduling of a hardreal time task is done by the task level scheduler which is based on Earliest Deadline First (EDF) scheduling policy. Our task level scheduler incorporates forcedirected scheduling methodology to address the situations where EDF is not optimal. The experimental results on a variety of examples show that the approach is highly effective and efficient.
From Dynamic Programming to Greedy Algorithms
 Formal Program Development, volume 755 of Lecture Notes in Computer Science
, 1992
"... A calculus of relations is used to reason about specifications and algorithms for optimisation problems. It is shown how certain greedy algorithms can be seen as refinements of dynamic programming. Throughout, the maximum lateness problem is used as a motivating example. 1 Introduction An optimisat ..."
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Cited by 14 (3 self)
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A calculus of relations is used to reason about specifications and algorithms for optimisation problems. It is shown how certain greedy algorithms can be seen as refinements of dynamic programming. Throughout, the maximum lateness problem is used as a motivating example. 1 Introduction An optimisation problem can be solved by dynamic programming if an optimal solution is composed of optimal solutions to subproblems. This property, which is known as the principle of optimality, can be formalised as a monotonicity condition. If the principle of optimality is satisfied, one can compute a solution by decomposing the input in all possible ways, recursively solving the subproblems, and then combining optimal solutions to subproblems into an optimal solution for the whole problem. By contrast, a greedy algorithm considers only one decomposition of the argument. This decomposition is usually unbalanced, and greedy in the sense that at each step the algorithm reduces the input as much as poss...
Complexity Results for SingleMachine Problems with Positive FinishStart TimeLags
 Computing
, 1998
"... In a singlemachine problem with timelags a set of jobs has to be processed on a single machine in such a way that certain timing restrictions between the finishing and starting times of the jobs are satisfied and a given objective function is minimized. We consider the case of positive finishstart ..."
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Cited by 12 (0 self)
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In a singlemachine problem with timelags a set of jobs has to be processed on a single machine in such a way that certain timing restrictions between the finishing and starting times of the jobs are satisfied and a given objective function is minimized. We consider the case of positive finishstart timelags l ij which mean that between the finishing time of job i and the starting time of job j the minimal distance l ij has to be respected. New complexity results are derived for singlemachine problems with constant positive timelags l ij = l which also lead to new results for flowshop problems with unit processing times and job precedences. Key words: complexity results, timelags, single machine, flowshop problem Supported by the Deutsche Forschungsgemeinschaft, Project `Komplexe MaschinenSchedulingprobleme ' 1 Introduction In a singlemachine problem a set of jobs j = 1; : : : ; n has to be processed without preemption on a single machine in such a way that at most one jo...
On Scheduling Atomic and Composite Multimedia Objects
 IEEE TRANSACTIONS ON KNOWLEDGE AND DATA ENGINEERING
, 1995
"... In multiuser multimedia information systems (e.g., videoondemand, newsediting) the policy employed to activate queued requests has a significant impact on the average startup latency observed by the users. In this paper, we view the retrieval of an object as a task and study the problem of sched ..."
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Cited by 11 (0 self)
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In multiuser multimedia information systems (e.g., videoondemand, newsediting) the policy employed to activate queued requests has a significant impact on the average startup latency observed by the users. In this paper, we view the retrieval of an object as a task and study the problem of scheduling such tasks. In this scheduling problem, tasks are IObound and each may utilize multiple disks. Each task acquires and releases disks in a regular manner based on the layout of its referenced object on the disks. In addition, there might be temporal relationships among multiple tasks that constitute a composite task. While previous studies have focused on both scheduling subtasks localized to a single disk (e.g., GSS [YCK92]) and determining the regular pattern of disk utilization per task (e.g., striping [BGMJ94]), the method for selecting a task for activation has received little attention. In this study, we formalize a class of task scheduling problems that arise in a large class of...