Showing papers on "Flow shop scheduling published in 1968"

Project scheduling with resource constraints.

Abstract: : Critical path and network flow techniques can solve project scheduling problems of a realistic size when there are no resource constraints; the introduction of the latter, however, changes the problem into one in which the number of variables and constraints depends on the number of time periods, and which existing methods can solve only for a very small size. The purpose of this paper is to reformulate the scheduling problem with resource constraints in a way that should eliminate the dependence of problem size on the number of time periods and should make this problem amenable to critical path - and network flow techniques. Thus, scheduling with resource constraints is shown to be equivalent to the problem of finding an optimal selection of arcs in a disjunctive graph with stability conditions. 'Simple' machine sequencing and machine sequencing with sets of identical machines are shown to be special cases of this model. The scheduling problem with resource constraints can thus be solved by generating a sequence of PERT networks which satisfy certain stability conditions. (Author)

A modified si rule in job shop scheduling

Abstract: SUMMARY A job shop is defined as a production centre consisting of several machines, each of which may be required for processing jobs of different makeups. The scheduling problem is concerned with determining the sequence in which these jobs should be processed on each machine, and this has led to several studies of alternative loading or priority rules. One rule, which has been found to be effective in reducing the average throughput time of jobs, is the SI rule, which can be described as follows: of jobs waiting in a queue to be processed on any given machine, select first the one with the shortest imminent processing time. The study described in this paper involved a simulation of a hypothetical shop with several machines. A number of alternative rules and variations on the SI rule were investigated. One modification of the SI rule called for the creation of two queues, one having a priority over the other and each queue involving an SI discipline. The decision as to which queue a job should belong to...

Operating Systems: On overcoming high-priority paralysis in multiprogramming systems: a case history

Abstract: High-priority paralysis is the degradation that can occur in multiprogramming systems when scheduling is based primarily on preassigned priorities. It can be alleviated by modifying the scheduling algorithm to maximize the number of programs active at one time. The case history given in this paper indicates two general methods by which simultaneity can be increased. Possible refinements in the scheduling algorithm for future improvements are considered briefly.

Job shop type production scheduling by simulation

Abstract: The primary purpose of this paper is to introduce the audience to a concept that is not always appreciated by those skilled in the art of simulation. In contrast to the traditional use of simulation as a study tool, the following discussion will emphasize the potential role of simulation for operational production scheduling in job shop-like environments rather than the research-oriented role now primarily assigned to it.Simulation techniques have been employed to study nearly all phases of the manufacturing process including forecasting, long-range planning, order release, and the flow of jobs on the production floor. This paper discusses production floor scheduling of discrete production facilities with job shop characteristics. A job shop is defined as having the following characteristics: 1)there is a set of production or service facilities; 2) jobs consisting of several tasks move between facilities for service; 3) one or more tasks are performed at each facility; 4) the service time for tasks may vary from job to job; and 5) the routing between facilities may vary from job to job.

Application of GPSS/360 to job shop scheduling

Abstract: Pertinent characteristics of the job shop scheduling problem are reviewed. Two GPSS/360 models assessing a total of eight alternative rules for constructing job shop schedules are presented. These rules have been studied by earlier investigators; hence this is a state-of-the-art paper illustrating the approach to an old problem using a relatively new capability, GPSS/360. Selected model output is exhibited, results are summarized, and assembly and execution times are indicated. Several references to appropriate earlier investigations are included. The models shown here are remarkably compact in comparison with earlier simulation models used to investigate the same or similar scheduling rules.