Showing papers on "Dynamic priority scheduling published in 1985"

A Time-Driven Scheduling Model for Real-Time Operating Systems.

Abstract: Process scheduling in real-time systems has almost invariably used one or more of three algorithms: fixed priority, FIFO, or round robin. The reasons for these choices are simplicity and speed in the operating system, but the cost to the system in terms of reliability and maintainability have not generally been assessed. This paper originates from the notion that the primary distinguishing characteristic of a real-time system is the concept that completion of a process or a set of processes has a value to the system which can be expressed as a function of time. This notion is described in terms of a time-driven scheduling model for real-time operating systems and provides a tool for measuring the effectiveness of most of the currently used process schedulers in real-time systems. Applying this model, we have constructed a multiprocessor real-time system simulator with which we measure a number of well-known scheduling algorithms such as Shortest Process Time (SPT), Deadline, Shortest Slack Time, FIFO, and a fixed priority scheduler, with respect to the resulting total system values. This approach to measuring the process scheduling effectiveness is a first step in our longer term effort to produce a scheduler which will explicitly schedule real-time processes in such a way that their execution times maximize their collective value to the system, either in a shared memory multiprocessing environment or in multiple nodes of a distributed processing environment.

Evaluation of a flexible task scheduling algorithm for distributed hard real-time systems

Abstract: Most systems which are required to operate under severe real-time constraints assume that all tasks and their characteristics are known a priori. Scheduling of such tasks can be done statistically. Further, scheduling algorithms operating under such conditions are usually limited to multiprocessor configurations. The authors present a scheduling algorithm which works dynamically and on loosely coupled distributed systems for tasks with hard real-time constraints; i.e., the tasks must meet their deadlines. It uses a scheduling component local to every node and a distributed scheduling scheme which is specifically suited to hard real-time constraints and other timing considerations. Periodic tasks, nonperiodic tasks, scheduling overheads, communication overheads due to scheduling and preemption are all accounted for in the algorithm. Simulation studies are used to evaluate the performance of the algorithm.

Multi-Project Scheduling: Analysis of Project Performance

Abstract: Application of heuristic solution procedures to the resource-constrained, multi-project scheduling problem is analyzed under equal and unequal penalties. The performance of ten scheduling rules is categorized with respect to four project summary measures, namely, resource-constrainedness, location of the peak requirements, and problem size. It is shown that the choice of a scheduling rule can be based upon the resource-constrainedness, problem size, and penalty. These results are based on scheduling, in detail, over 3000 multi-project scheduling problems, each containing three projects and from 24 to 66 activities.

Method and apparatus for scheduling the execution of multiple processing tasks in a computer system

Abstract: A task schedular for scheduling the execution of a plurality of tasks within a computer system. The task scheduler utilizes a combination of externally assigned priorities and internally calculated priorities to optimize the responsiveness of the computer to external interactions.

Stability and Distributed Scheduling Algorithms

Abstract: Many distributed scheduling algorithms have been developed and reported in the current literature. However, very few of them explicitly treat stability issues. This paper first discusses stability issues for distributed scheduling algorithms in general terms. Two very different distributed scheduling algorithms which contain explicit mechanisms for stability are then presented and evaluated with respect to individual specific stability issues. One of the agorithms is based on stochastic learning automata and the other on bidding. The results indicate how very specific the treatment of stability is to the algorithm and environnent under consideration.

Analysis of flexible manufacturing systems with priority scheduling: PMVA

Abstract: A new methodology for performance analysis of flexible manufacturing systems (FMSs) with priority scheduling is presented. The analytic model developed extends the mean value analysis of closed networks of queues with multiple product types, various non-preemptive priority service disciplines, and with parallel machine stations. Performance measures derived include the expected throughput per product and per station, utilization of machines and transporters, queuing times and queue length measures for various configurations. Extensive numerical calculations have shown that the algorithm used for solving the problem converges rapidly and retains numerical stability for large models. The paper also illustrates the application of the model to a system with a mixture of FCFS and HOL disciplines which gives insights into various priority assignment policies in FMSs. Special attention was given to the problem of scheduling the robot carriers (transporters).

A Graph Partitioning Approach to Airline Crew Scheduling

Abstract: In this paper, we present a computerized procedure for scheduling airline crews. The procedure performs set partitioning on a graph by decomposing the problem into a series of subproblems which are solved as matching problems. Computational tests of the algorithm reveal consistent performance in producing efficient solutions to the air crew scheduling problem.

Cyclo-static multiprocessor scheduling for the optimal realization of shift-invariant flow graphs

Abstract: Cyclo-static processor solutions overcome the weaknesses of systolic processors and of SSIMD and PSSIMD solutions for the class of algorithms that can be described by cyclic shift-invariant flow graphs. Cyclo-static solutions are a broad family of processor (efficiency) optimal, synchronous, multiprocessor realizations that by appropriate design choices can be rate optimal, input-output delay optimal and communications optimal. For a given algorithm the cyclo-static family of solutions contains many classes which includes SSIMD and PSSIMD solutions as special cases, when they exist.

An Optimal Instruction-Scheduling Model for a Class of Vector Processors

Abstract: An integer programming model that portrays the architectural features of a class of vector and array processors has been developed. This model is used to produce optimal schedules for low-level-instruction codes of such processors. Optimal schedules are produced for both straight codes and instruction loops. Loop scheduling is separately considered because of special consideration that must be given to the effects of the instructions of consecutive loop iterations on each other that are hidden when static instruction scheduling approach is used. Using the model, a number of experiments have been conducted in optimal scheduling of Cray assembly codes.

An Algorithm for Scheduling a Large Pumped Storage Plant

Abstract: The Michigan Electric Coordination Center (MEPCC), operated by Consumers Power and Detroit Edison Companies, has the responsibility for scheduling the Ludington pumped storage plant. Ludington has an extremely large economic effect on the Consumers Power and Detroit Edison Companies' system due to its size (over 1800 MW net demonstrated generating capability). This paper presents a dynamic programming algorithm for scheduling large pumped storage plants and shows how this method can be coordinated with the commitment of the thermal units of the system.

Optimal Scheduling of Periodic Activities

Abstract: This paper studies the scheduling of multiple activities that require periodic processing on a single facility for an infinite horizon. It first formulates this scheduling problem as an integer linear programming (ILP) model, and then uses the Chinese Remainder Theorem to efficiently partition the original into smaller independent models. For a small problem involving about 10 activities, the solution can be obtained very simply by hand. An example is given to illustrate the approach.

Technical Note-Optimal Scheduling of Periodic Activities

Abstract: This paper studies the scheduling of multiple activities that require periodic processing on a single facility for an infinite horizon. It first formulates this scheduling problem as an integer linear programming ILP model, and then uses the Chinese Remainder Theorem to efficiently partition the original into smaller independent models. For a small problem involving about 10 activities, the solution can be obtained very simply by hand. An example is given to illustrate the approach.

Dynamic model for scheduling maintenance of transportation facilities

Abstract: The optimum scheduling of maintenance for transportation facilities is addressed. The problem is described as a multiple-period resource allocation problem with constraints on both resource availability and state and decision variables. The problem is formulated as a nonlinear optimization problem and solved by using the generalized reduced gradient method. The model uses recursive formulas similar to those used in dynamic programming in order to calculate the partial derivatives of the objective function. The model is applied to an example based, in part, on actual data provided by the Japanese National Railways. Several tests are made to show the performance of the model, and the results are compared with those of two alternative solutions. The results show the usefulness of the model in a wide variety of applications and its superiority to the alternative solutions examined.

The two-processor scheduling problem is in R-NC

Abstract: The two-processor scheduling problem is perhaps the most basic problem in scheduling theory, and several efficient algorithms have been discovered for it. However, these algorithms are inherently sequential in nature. We give a fast parallel (R-NC) algorithm for this problem. Interestingly enough, our algorithm for this purely combinatoric-looking problem draws on some powerful algebraic methods.

Stability and distributed scheduling algorithms

Abstract: Many distributed scheduling algorithms have been developed and reported in the current literature. However, very few of them explicitly treat stability issues. This paper first discusses stability issues for distributed scheduling algorithms in general terms. Two very different distributed scheduling algorithms which contain explicit mechanisms for stability are then presented and evaluated with respect to individual specific stability issues. One of the agorithms is based on stochastic learning automata and the other on bidding. The results indicate how very specific the treatment of stability is to the algorithm and environnent under consideration.

Cru-sched--a computer based bus crew scheduling system using integer programming. from the book computer scheduling of public transport 2

Abstract: The crew scheduling system CRU-SCHED developed by the authors and implemented by Coras Iompair Eireann is described. Traditional approaches to crew scheduling via set partitioning and set covering are extended to a model which is more applicable to the scheduling task. The scheduling system is designed to be easy to use by schedulers with little computer experience. The system is menu driven and provides comprehensive data processing support including the provision of screen forms for data entry and amendment. The experience of regular use of the system has demonstrated the success of this approach to crew scheduling.

Enhancements to the hastus crew scheduling algorithm. from the book computer scheduling of public transport 2

Abstract: This paper provides an update to an earlier description of the HASTUS algorithm. It describes improvements which have already been implemented (e.g. the marching algorithm) and other improvements still under research and development.

Capacity Allocation in Multiple Access Networks

Abstract: The theoretical issues of scheduling for capacity allocation in multiple access networks using in-band and out-of-band signaling are addressed. The analysis is carried out under the hypothesis that the "scheduling epochs" consist of bandwidth-dependent and bandwidthindependent components. The ultimate limitation on channel capacity rests with the bandwidth-independent component. It is shown that over the range of practical interest, scheduling using a separate side channel is superior to in-band scheduling in that, under similar conditions, the former attains a higher usable channel capacity.

A Multifactor Priority Rule for Jobshop Scheduling Using Computer Search

Abstract: Priority rules are widely used in jobshop scheduling to determine the sequence in which jobs are to be processed. The research in this area has been directed at developing generally applicable priority rules. This paper presents a method for determining an effective priority rule specific to the jobshop scheduling problem to be solved. First, a generalized objective function is formulated which is the sum of costs of tardiness, carrying in-process inventory and machine idleness. Second, a multifactor priority rule is developed which is a weighted average of four factors used in simple priority rules. Third, a method is presented for using a computer search technique to determine the best weights to use in the priority rule. Finally, a computer simulation for testing this approach versus using other priority rules is described and the experimental results are reported.

On some matching problems arising in vehicle scheduling models

Abstract: Two bipartite matching problems arising in Vehicle Scheduling are considered: the capacitated matching and the multicommodity matching. For the former, given a reasonable cost structure, we can exhibit a polynomial time algorithm, while the general case is conjectured to be NP-hard. The latter problem is shown to be NP-hard. A heuristic algorithm based on Lagrangean relaxation for the capacitated version of the multicommodity matching is also presented together with experimental results.