Showing papers on "Dynamic priority scheduling published in 1982"

On Manpower Scheduling Algorithms

Abstract: This paper provides a systematic review of several of the available manpower scheduling algorithms from a common framework. The five-stage framework is based on the recognition that the general scheduling problem can be decomposed into five separate but related subproblems or stages, namely, the determination of temporal manpower requirements, total manpower requirement, recreation blocks, recreation/work schedule, and shift schedule. One or more general models are developed at each stage to categorize the problem formulation(s) suggested by the various algorithms. Additionally, the algorithms are compared and their stage-specific solution methods are discussed.

Job shop scheduling heuristics and frequency of scheduling

Abstract: This paper presents a job scheduling problem. Two important aspects are included in the subsequent analysis. The first is the dynamic nature whereby new jobs arrive to be included intermittently through time. The second is the uncertainty, or error in estimating process times, and the likelihood of machine breakdown. An experiment is presented which shows the performance of a number of heuristics in the form of dispatching disciplines under different scheduling conditions which are determined by the scheduling period and the level of uncertainty in the process times and machine breakdowns. Various different measures of performance which could be of importance to management are considered. These include mean ratio of flow time to process time, mean queueing time, mean lateness, percentage of jobs late and net CPU times required to generate schedules in the simulation process. Results are presented showing the relationship between the performance of the heuristics relative to the different measures...

Priority Scheduling Rules for Repairable Inventory Systems

Abstract: Improved priority scheduling rules are presented for a repair shop supporting a multi-item repairable inventory system with a hierarchical product structure. A variety of scheduling rules are evaluated using a simulation of a representative shop and product structure. The results indicate that dynamic rules which use inventory status information perform better than other dynamic or static rules which ignore inventory status; moreover, dynamic rules which use work-in-process inventory information outperform dynamic rules which ignore work-in-process inventory levels. In the simulation, the use of improved scheduling rules provides performance equivalent to a 20% reduction in spares inventory.

The Two-Product, Single-Machine, Static Demand, Infinite Horizon Lot Scheduling Problem

Abstract: In this paper, we deal with the two-product, single-machine, static demand, infinite horizon lot scheduling problem. After a quick review of the literature, the necessary and sufficient conditions for feasibility are derived without imposing any preliminary requirements. Then, an optimal solution algorithm is presented. Finally, we show that a necessary condition for the feasibility of N-product schedules is that each cycle time be an integer multiple of some basic cycle time.

On Scheduling Independent Tasks with Restricted Execution Times

Abstract: We consider the problem of nonpreemptively scheduling n independent tasks on m identical and parallel machines with the objective of minimizing the overall finishing time. The problem has been shown to be NP-complete in the strong sense and hence there probably will not be any pseudopolynomial time algorithm for solving this problem. We show, however, that if the execution times are restricted to a fixed number, say k, of different values, then it can be solved in polynomial time. Our algorithm can be implemented to run in time 0log2p * log2m * n2k-1 and space 0log2m * nk-1 in the worst case, where p is the largest execution time.

Machine Scheduling with Precedence Constraints

Abstract: Machine scheduling theory is concerned with the allocation over time of scarce resources in the form of machines or processors to activities known as jobs or tasks. If the jobs can be performed in any order, they are said to be independent. However, this is often not the case; technological or other constraints may dictate that of two given jobs one must be performed before the other. Such precedence constraints of course impose a partial ordering on the jobs.

Note-On Anomalies in Dynamic Ratio Type Scheduling Rules: A Clarifying Analysis

Abstract: Previous authors have shown that dynamic ratio scheduling rules do not always behave as intended. A recent proposal by Adam and Surkis Adam, N. R., J. Surkis. 1980. Priority update intervals and anomalies in dynamic ratio type job shop scheduling rules. Management Sci.26 12, December 1227-1237. to correct such anomalies is shown to be in error. The reason why such anomalies occur is clarified and a rule which prevents such anomalies is presented.

Dominant Strategies in Stochastic Allocation and Scheduling Problems

Abstract: Some problems of stochastic allocation and scheduling have the property that there is a single strategy which minimizes the expected value of the costs incurred up to every finite time horizon. We present a sufficient condition for this to occur in the case where the problem can be modelled by a Markov decision process with costs depending only on the state of the process. The condition is used to establish the nature of the optimal strategies for problems of customer assignment, dynamic memory allocation, optimal gambling, maintenance and scheduling.

A Dual Heuristic for Vehicle Scheduling

Abstract: A heuristic method is used to solve the vehicle scheduling problem by maintaining local optimality whilst approaching the feasible region. Tests with published problems show that the technique gives results comparable with the best published algorithms. The practical requirements of real life scheduling are discussed, and the flexibility of the technique is demonstrated for a complex problem involving weekly cyclical deliveries.

A Stochastic Approach to Hierarchical Planning and Scheduling

Abstract: This paper surveys recent results for stochastic discrete programming models of hierarchical planning problems. Practical problems of this nature typically involve a sequence of decisions over time at an increasing level of detail and with increasingly accurate information. These may be modelled by multistage stochastic programmes whose lower levels (later stages) are stochastic versions of familiar NP-hard deterministic combinatorial optimization problems and hence require the use of approximations and heuristics for near-optimal solution. After a brief survey of distributional assumptions on processing times under which SEPT and LEPT policies remain optimal for m-machine scheduling problems, results are presented for various 2-level scheduling problems in which the first stage concerns the acquisition (or assignment) of machines. For example, heuristics which are asymptotically optimal in expectation as the number of jobs in the system increases are analyzed for problems whose second stages are either identical or uniform m-machine scheduling problems. A 3-level location, distribution and routing model in the plane is also discussed.

Two-Operation Crane Scheduling Problems

Abstract: For two-operation crane scheduling problems we consider two basic procedures; namely, batching and meshing. A minimum-ordered partition forms the basis of the batching procedure. A mesh-ordered relation forms the basis of the meshing procedure. Under certain necessary conditions, these procedures yield optimal schedules. Examples are provided to illustrate each procedure. Four mixed procedures are defined and combined to form an efficient algorithm whose solution is no worse than 4/3 the optimal solution.

Improved 0/1-interchange scheduling

Abstract: Consideration is given to the problem of nonpreemptively scheduling a set ofN independent tasks to a system ofM identical processors, with the objective to minimize the overall finish time. It is proved that the 0/1-INTERCHANGE scheduling heuristic can be modified, without increasing its time complexity fromO(N logM), so that its worst-case performance bound is reduced from 2 to 4/3 times optimal.

Critical Path Scheduling with Resource and Processor Constraints

Abstract: An investigation is made of the worst-case performance of two related algorithms for scheduling unit-execution-time task systems with resources. Unlike most previous scheduling results for task systems with resources, it is assumed that there are a fixed number of processors in the system. This assumption has both practical and theoretical interest. An upper bound is given for the worst-case performance of critical path scheduling for these task systems. This bound depends on both the number of processors and the number of resources. Moreover, it is shown that this is (asymptotically) the best possible upper bound. It is also noted that exactly the same bound holds for the worst-case performance of Coffman-Graham scheduling. 13 references.

Complexity and Solutions of Some Three-Stage Flow Shop Scheduling Problems

Abstract: It is well known that the minimal length non-preemptive scheduling problem for the general three-stage flow shop is NP-complete. This paper presents a study of a special type of flow shop in which a particular stage of each job is the longest (or the shortest as the case may be). In most cases, it is found that the problem remains strongly NP-complete. In other cases, polynomial scheduling algorithms are presented.

A linear time algorithm to minimize maximum lateness for the two-machine, unit-time, job-shop, scheduling problem

Abstract: A linear time algorithm is given for the two-machine, job-shop scheduling problem with n unit-time tasks in which maximum lateness is to be minimized. This algorithm generalizes a linear time algorithm for the corresponding makespan problem given by HEFETZ and ADIRI and improves an O(n log n)-algorithm developed by the author.

Deterministic and stochastic scheduling : proceedings of the NATO Advanced Study and Research Institute on Theoretical Approaches to Scheduling Problems, held in Durham, England, July 6-17, 1981

Abstract: I. Advanced Study Institute Proceedings.- Worst-Case Analysis of Heuristic Algorithms for Scheduling And Packing.- Recent Developments in Deterministic Sequencing and Scheduling: A Survey.- On Scheduling with Release Times and Deadlines.- Scheduling Uniform Machines with Release Times, Deadlines and Due Times.- Preemptive Scheduling of Precedence-Constrained Jobs on Parallel Machines.- Forwards Induction and Dynamic Allocation Indices.- Multiserver Stochastic Scheduling.- Stochastic Shop Scheduling: A Survey.- Multi-Server Queues.- Queueing Networks and their Computer System Applications: An Introductory Survey.- Stationary Properties of timed Vector Addition Systems.- The Multiproduct lot Scheduling Problem.- An Introduction to Proof Techniques for Bin-Packing Approximation Algorithms.- A Stochastic Approach to Hierarchical Planning and Scheduling.- On Stochastic Analysis of Project-Networks.- II. Advanced Research Institute, Proceedings.- Probabilistic Analysis of the Lpt Processor Scheduling Heuristic.- Sequential Project Selection (Multi-Armed Bandits) and the Gittins Index.- Dominant Strategies in Stochastic Allocation and Scheduling Problems.- On the Computational Complexity of Stochastic Scheduling Problems.- Deterministic and Stochastic Scheduling Problems with Treelike Precedence Constraints.- On the Evaluation of Non-Preemptive Strategies in Stochastic Scheduling.- Sequential Open-Loop Scheduling Strategies.- On the Delay Functions Achievable by Non-Preemptive Scheduling Strategies in M/G/L Queues.- Modelling for Multiprocessor Projects.- Addresses of Authors.- Name Index.

Distributed scheduling of resources on interconnection networks

Abstract: In this paper, we have studied the distributed scheduling of resources on interconnection networks. The resource scheduling problem is different from the conventional address mapping problem on interconnection networks because a request is not directed towards a particular destination address but to any one of a pool of destination addresses for free resources. To design an algorithm with the minimum transfer of control signals, priority is associated with the scheduling of multiple requests. This is illustrated by the distributed cross-bar switch which has one signal line in each direction of a switch node. For complete asynchronous operation, more signal lines are needed. This is illustrated by the distributed Omega and binary n-cube networks. Each exchange box in the network operates independently to resolve conflicts. The performance of the distributed scheduling algorithm for the Omega and cube networks is compared against the optimal centralized scheduling algorithm which has about 1% average blocking probability. The performance degradation is less than 20% in all cases. The theory of the design can be applied to other interconnection networks.

A multi-microprocessor architecture with hardware support for communication and scheduling

Abstract: We describe a multiprocessor system that attempts to enhance the system performance by incorporating into its architecture a number of key operating system concepts. In particular:— the scheduling and synchronization of concurrent activities are built in at the hardware level,— the interprocess communication functions are performed in hardware, and,— a coupling between the scheduling and communication functions is provided which allows efficient implementation of parallel systems that is precluded when the scheduling and communication functions are realized in software.

Multiple pipeline scheduling in vector supercomputers

Abstract: A parallel task scheduling model is proposed for multipipeline vector processors. This model can be applied to explore maximal concurrency in vector computers, such as the Cray-1, Cyber-205, Star-100, TI-ASC, and IBM 3838. The optimisation problem of simultaneously scheduling multiple pipelines with vector tasks is shown to be np-complete. Thus, several heuristic scheduling algorithms, which can be easily implemented in vector processors with low system overhead and high throughput performance, have been developed. 17 references.

Large scale implementation of a time oriented vehicle scheduling model

Abstract: The objective of this research project was the development of a vehicle scheduling model with three special properties: 1) the ability to solve large scale vehicle scheduling problems with time window and time dependent customer demand constraints; 2) the capability of being integrated within the Computer Assisted Routing, Scheduling, and Dispatching/Management Information System (CARSD/MIS) currently being developed by the Transportation Administration of Dade County, Florida for UMTA as a prototype for other coordinated paratransit services; and 3) the ability to provide operational solutions to vehicle scheduling problems obtained from the research literature and from CARSD/MIS database. This document reports the development of a time oriented vehicle scheduling model. The model is unique in its ability to incorporate easily time window and time dependent customer demand constraints. Solutions to the model are obtained through the use of a branch and bound procedure. A disjunctive graph model, similar to those employed in activity and job shop scheduling, is used in the solution procedure to obtain bounding information. The efficacy of this procedure is demonstrated on vehicle scheduling problems obtained from the research literature. The authors state that although the current implementation of the time oriented vehicle scheduling algorithm has been developed to meet the operational requirements of the scheduling module of the CARSD/MIS system, delays in the CARSD/MIS project prevented the required operational interface and testing.

A Hardware Task Scheduling Mechanism for a Real-Time Multi-Microprocessor Architecture.

Abstract: Efficient task scheduling and resource allocation schemes which take advantage of concurrent operations are crucial to the use of multiple microprocessor architectures in real-time applications. Since the data processing overhead associated with algorithmic scheduling mechanisms increases as the number of processors and tasks within the system increases, these scheduling mechanisms could prove to be the limiting factor on a machine's real-time performance capabilities. This paper presents the design of a hardware task scheduler, which by the efficient routing of control tokens, is able to map a problem space onto a distributed architecture. A possible single-chip implementation of the task scheduler and a discussion of the scheduler's expected performance is also presented. 7 references.