Showing papers on "Scheduling (computing) published in 1975"

A Comparison of Heuristic and Optimum Solutions in Resource-Constrained Project Scheduling

Abstract: The problem addressed is that of scheduling the activities of a project network to minimize project duration under conditions of multiple limited resource requirements and availabilities. Various heuristic sequencing rules have been applied to this problem, and the effectiveness of these rules relative to one another has been previously compared in the literature. However, there have been no previous comparisons of the effectiveness of these rules relative to an optimum solution. This paper makes such a comparison of eight different heuristic scheduling rules, including those found most effective in previous research on this problem. Results are presented for a total of eighty-three different multi-resource problems.

Dynamic Scheduling of a Multiclass Queue: Discount Optimality

Abstract: We consider a single-server queuing system with several classes of customers who arrive according to independent Poisson processes. The service time distributions are arbitrary, and we assume a linear cost structure. The problem is to decide, at the completion of each service and given the state of the system, which class (if any) to admit next into service. The objective is to maximize the expected net present value of service rewards received minus holding costs incurred over an infinite planning horizon, the interest rate being positive. One very special type of scheduling rule, called a modified static policy, simply enforces a (nonpreemptive) priority ranking except that certain classes are never served. It is shown that there is a modified static policy that is optimal, and a simple algorithm for its computation is presented.

Generator maintenance scheduling via successive approximations dynamic programming

Abstract: Host currently used thermal-generator maintenance scheduling methods schedule each unit at a time, leading in many cases to a poor local optimum or to an unfeasible solution. Considering simultaneously all units in the scheduling process, a computationally impractical method results. In this paper a piece-wise compromising method of solution is presented, which conveniently groups generating units and uses successive approximations dynamic programming. The optimal maintenance scheduling problem is formulated by employing a suitable state-space representation; most common constraints used in practice are described and a multiple objective function is presented. The effectiveness of the optimizing method is illustrated by solving a problem with data obtained from a real system. The grouping criterion presented appears to be the cornerstone of the superior performance of the proposed method.

A Preliminary Evaluation of the Critical Path Method for Scheduling Tasks on Multiprocessor Systems

Abstract: The problem of scheduling tasks on a system of independent identical processors is discussed and the performance of a suboptimal method is evaluated. The computation is modeled by an acyclic directed graph G(T,<), where node set T represents the set of tasks to be completed and edge set < defines the precedence between tasks. The objective is to minimize the finishing time of the computation graph. Known theoretical results are reviewed and a general branch-and-bound algorithm for finding optimal solutions is presented. The schedules produced by a simple critical path priority method are shown to be near optimal for randomly generated computation graphs.

A Queuing-Linear Programming Approach to Scheduling Police Patrol Cars

Abstract: In any city the arrival rate of calls for police patrol-car service varies considerably through the day. Using queuing theory and integer linear programming, we present a method for scheduling patrol cars so that specified service standards are met at each hour of the day. Two models are used. The first is an M/M/n queuing model with time-dependent parameters that is solved numerically. The second is an integer linear program in which the decision variables are the number of patrol cars working each tour and the times at which they go out of service for meals. The program's constraints are determined by the output of the queuing model. Use of the method with data from the New York City Police Department indicates that it can lead to substantial improvements in police service.

Project Network Summary Measures Constrained- Resource Scheduling

Abstract: This paper describes some summary measures which might be used in specifying the size, shape, logic, time and resource characteristics of project networks of the PERT/CPM type. The results of an investigation to determine relationships between some selected such measures and project duration increase under constrained-resource scheduling are presented, and procedures for estimating project duration increase in advance of scheduling are described.

Fundamentals of operating systems

Abstract: Functions and characteristics of an operating system concurrent processes the system nucleus memory management input and output the filing system resource allocation and scheduling protection reliability job control graphical user interfaces.

Critical Ratio Scheduling: An Experimental Analysis

Abstract: Critical Ratio scheduling has been implemented in job shops that manufacture component parts for stock replenishment as well as direct customer orders. Proponents of this technique argue that scheduling performance is improved by gathering and processing two different types of operating information on a routine basis for use in making priority scheduling decisions: queue waiting time information for individual machines and stock status information from the shop's inventory system. Simulation experiments are reported here which describe the effect on the performance of a shop and its associated inventor' system when using this type of information with an Order Point inventory control system. The results indicate that the additional information provided by the increased data collection and processing functions does not contribute a statistically significant improvement in the overall performance of the production system.

Scheduling with earliest start and due date constraints on multiple machines

Abstract: We consider the scheduling of n jobs on m identical machines when the jobs become available for processing at ready times ai, ai, ⩾ 0, require di time units for processing and must be completed by times bi for i = 1, 2, … n. The objective chosen is that of minimizing the total elapsed time to complete all jobs subject to the ready time and due date constraints, preemption is not allowed. We present a multi-stage solution algorithm for this problem that is based on an implicit enumeration procedure and also uses the labelling type algorithm which solves the problem when preemption is allowed.

Adaptive optimization of a time-sharing system's performance

Abstract: The complex task of managing a virtual memory multiprogramming system is considered as one which can be achieved by allowing the operating system to make use of measurement data gathered on-line in the scheduling decisions it has to make. System performance optimization is achieved by continuous monitoring of critical system parameters and workload characteristics and by use of this information in a real-time adaptive feedback control policy. As a specific application of this approach, the maximization of system throughput by the regulation of the degree of multiprogramming in a virtual memory system is examined. The specific form of this performance measure as a function of the number of active processes sharing main memory is used in the design of an adaptive and statistical maximum-seeking algorithm designed to respond to abrupt changes in program locality. The data gathering and smoothing procedures and the optimization policy are then implemented in a simulator of a virtual memory time-sharing system and evaluated in simulation runs with a random and time-varying workload. These experiments are used to tune the various parameters of the algorithm and to demonstrate its ability to maintain the system at an optimal level of performance. Statistical confidence intervals for these simulation runs are given in order to provide a measure of significance to the experiments.

Coordinating Aggregate and Detailed Scheduling in the One-Machine Job Shop: II—Computation and Structure

Abstract: A previous research report of the authors presented a formal model of the one-machine job-shop scheduling problem with variable labor capacity. This report presents some computational experience with the algorithm proposed previously and a discussion of the structural aspects of the problem. Extensions and refinements of the algorithm are introduced to deal with nonsimultaneous job arrivals and the production smoothing problem. These results provide insight into the structure of the aggregate-detailed cost trade-off problem and suggest a good heuristic decision rule for problems of realistic size and complexity.

A heuristic algorithm for resource leveling in multi-project, multi-resource scheduling

Abstract: The utility of conventional project management techniques, such as PERT and CPM, is hampered by significant and realistic network attributes and managerial considerations. There are many situations which involve more than one project and numerous resources. Of major concern in such situations is the reduction of the maximum quantity of each required resource. The algorithm presented here is capable of scheduling the individual activities in multiple projects with multiple resources and leveling the overall quantity of each resource which is required. The basis of the algorithm is a sequencing procedure for examining various combinations of activity start times. The measure of effectiveness for each combination is the sum of the squares of the required quantity of each resource in each time period.

On Scheduling Chains of Jobs on One Processor with Limited Preemption

Abstract: A scheduling rule is given for determining the processing order of tasks which have the precedence structure of chains. It is assumed that the service times follow known distributions, that they are all independent, that costs are accrued by tasks at a constant rate until their service requirements are satisfied, that all the tasks are available at time 0 and that the service is interruptible at task-specific sets of points. The rule consists of computing for each chain an “optimal assignment” for its tasks and a rank function which depends on this assignment. Choosing at each point in time the chain with the smallest rank produces an optimal schedule. It is proved that the “optimal assignments” have the desirable property that as long as a task does not exceed its allotted service time, no preemption should take place.

Apparatus and method for schedule monitoring and control

Abstract: For the scheduling of activities, particularly construction activities by the Critical Path Method, an apparatus is provided with a mechanical simulation of the network associated with the method, and is adapted to support a network chart of activities and events. It has a progress bar for monitoring such activities and events, which is power driven at a constant rate for indicating the scheduled progress of the entire project at any given time, whereby the scheduler can determine at a glance at the board what adjustments, if any, need be made in the timing and progress of the various activities of the project.

Optimal schedules for special structure flowshops

Abstract: This paper considers the problem of scheduling a given number of jobs on a specified number of machines in a flowshop where the objective function is to minimize the total throughput time in which all jobs complete processing on all machines. Based on the combinatorial analysis of the problem, several simple algorithms are developed for solving special structure flowshop scheduling problems where the process times are not completely random, but bear a well-defined relationship to one another. The proposed algorithms are both simple and computationally efficient and can optimally solve large-sized problems even with manual computational devices.

The Utah TENEX scheduler

Abstract: A scheduling algorithm which is a modification of the standard TENEX scheduler is described. This algorithm differs from those commonly used in time-sharing systems in that it treats the case of multiple critical resources. The Utah scheduler considers CPU usage and real core occupancy, but the same techniques can be applied to cases of more than two critical resources. Similar scheduling tehniques can be applied to interactive batch-processing systems and to resource sharing systems.

Selecting a scheduling rule that meets pre-specified response time demands

Abstract: In this paper we study the problem of designing scheduling strategies when the demand on the system is known and waiting time requirements are pre-specified. This important synthesis problem has received little attention in the literature, and contrasts with the common analytical approach to the study of computer service systems. This latter approach contributes only in-directly to the problem of finding satisfactory scheduling rules when the desired (or required) response-time performance is specifiable in advance.

An algorithm for scheduling parallel processors

Abstract: SUMMARY This paper deals with optimal scheduling of jobs on identical parallel processors. The paper develops an algorithm for determining the optimal schedule and gives a proof of the algorithm. The criterion used is that of minimizing the total cost for processing all jobs when the jobs are assigned non-decreasing waiting costs which are non-linear. Extension of the algorithm for jobs with due dates is also given. Computational results are given which indicate the effectiveness of the algorithm as compared to complete enumeration.

Models of memory scheduling

Abstract: Queueing theoretic models of single and multi-processor computer systems have received wide attention in the computer science literature. Few of these models consider the effect of finite memory size of a machine and its impact on the memory scheduling problem. In an effort to formulate an analytical model for memory scheduling we propose four simple models and examine their characteristics using simulation. In this paper, we discuss some interesting results of these simulations.

Job Shop Scheduling with Due Dates and Operation Overlap Feasibility

Abstract: The job shop problem with due dates is formulated to allow overlaps among successive operations on a job. Multiple transports of sub lots and existence of setup times are two applications where this formulation can result in technologically feasible schedules. A procedure is described for generating overlap schedules and it is applied to eight test problems from the literature. The resulting schedules are compared to alternative schedules involving tardiness or overtime. The results indicate that the procedure is effective in generating multiple transport schedules for the manager's consideration. The comparative data provide useful tradeoff information for evaluation of alternatives and indicate that multiple transport scheduling may sometimes be a very economical way to try to meet due dates without using overtime operations.

Scheduling a Single Machine System: A Multi-product Multi-item Case

Abstract: A scheduling problem having the characteristics: is reported in this paper. A systematic procedure is presented for tackling such scheduling problems. An example has been solved to illustrate the method.

On Two—Processor Scheduling of One— or Two—Unit Time Tasks with Precedence Constraints

Abstract: This paper is concerned with the problem of scheduling on two processors tasks with 1- or 2-unit execution time and having arbitrary precedence constraints. An analysis is made of the algorithm (called f LPTS-schedule) which chooses as the next task to be scheduled, that task for which the sum of the execution times of all its successors is maximal. It is shown that LPTS produces a schedule with an error where f * and f are the finish times of an optimal and LPTS schedules, respectively. An example is given which shows that the error bound is tight, even for the case when all tasks have 1-unit execution time. A comparison of the LPTS algorithm with other scheduling algorithms is also presented.

An implicit enumeration algorithm for complex scheduling problems

Abstract: Several algorithms have been presented for handling complex scheduling problems. These methods are computationally impractical when confronted with large problems. New algorithms have been developed for solving job-shop problems. They are more efficient than the previous ones because they use dominance and better bound ideas. The purpose of this paper is to present an efficient algorithm for complex scheduling problems generalizing those ideas.

Capacity Bounds for Multi-Resource Queues

Abstract: A multi-resource queueing system is a single congestion point associated with a number of resources which may be of different types. Arriving jobs require some combination of these resources simultaneously for the duration of the processing time of the job. The capacity bound for such a system, given the characteristics of the input -stream. is defined as the smallest input rate which is guaranteed to saturate the system regardless of the scheduling rule which is employed. An algorithm for calculating this bound is presented which also specifies the proportion of time that the system should spend in processing various job combinations in order to achieve the capacity bound. The implications of this result are discussed for a number of resource allocation problems arising in computer systems.

A semantic model for parallel systems with scheduling

Abstract: This paper presents a semantic model for parallel systems with a scheduling mechanism that is useful for expressing and proving a wider range of properties than semantic models that do not consider scheduling.We formally describe a number of properties related to scheduling and deadlock, including "Fairness" and "Fullness", and show that schedulers with these properties behave in desirable ways.Lastly, we prove and conjecture some proof rules for scheduled systems and outline briefly the relation of this work to modelling protection in parallel systems.

Parallel processing : proceedings of the Sagamore Computer Conference, August 20-23, 1974

Abstract: On a class of scheduling algorithms for multiprocessors computing systems.- Scheduling unit-time tasks with limited resources.- Programmable radar signal processing using the RAP.- Analysis and design of a cost-effective associative processor for weather computations.- The implementation of APL on an associative processor.- A unified associative and von-neumann processor EGPP and EGPP-array.- Discriminating content addressable memories.- A fundamental theorem of asynchronous parallel computation.- The hyperplane method for an array computer.- Syntactic recognition of parallel processes in formally defined complexes of interacting digital systems.- A control structure for parallel processing.- Toward the design of a network manager for a distributed computer network.- The typeset-10 message exchange facility a case study in systemic design.- Optimal resource allocation and scheduling among parallel processes.- A recognizer and post-recognizer for optimizing execution times of programs.- Analytic and implementation considerations of two-facility sequencing in computer systems.- Computer models with constrained parallel processors.- Implementation of data manipulating functions on the staran associative processor.- Mixed mode arithmetic for STARAN.- Aapl: An array processing language.- The evolution of a parallel active tracking program.- Implementation of the AWACS passive tracking algorithms on a Goodyear STARAN.- Experiences with an operational associative processor.- Matrix computations on an associative processor.- Optimal searching algorithms for parallel-pipelined computers.- A new parallel algorithm for network flow problems.- Parallel processing by virtual instruction.- An approach to restructurable computer systems.- On programmable parallel data routing networks via cross-bar switches for multiple element computer architectures.- A reconfigurable parallel arithmetic unit.- Architectural considerations in interfacing a parallel processor to the air traffic control system.- An efficient implementation of conflict prediction in a parallel processor.- An associative processor architecture for air traffic control.- Application of an associative processor to aircraft tracking.- Analysis of parallel processing for air defense and air traffic control for Thailand.