Julian Reitman

The winter simulation conference: perspectives of the founding fathers

In this paper the General Chairs and Program Chairs of the Winter Simulation Conference (WSC) during the period 1967–1974 continue the discussion started in the Keynote Address on the past, present, and future of WSC and the field of simulation.

The Engineering Role of Simulation

Engineers involved in the design and analysis of complex systems can use computer simulation as a systems analysis and synthesis tool. Discrete-event simulation, coupled with dynamic display while the model runs on the computer, provides new opportunities for insight into complex systems. One higher order simulation language GPSS was used as a foundation upon which were added data bases, human interactivity, and display graphics. Through the use of these additions, the user can dynamically interact with the system being simulated. While the simulation is in progress, a series of pictorial representations of the system are presented. These may be stopped, restarted with new data, or continued at the users command. To extend the simulation capability to include continuous system aspects, GPSS was coupled to a high-order continuous simulation language CSMP.

Production Management Information System

A Management Information System has been developed and implemented using General Purpose Simulation System (GPSS)/360. The system provided the following data for a solid-state production facility: 1) current location of wafers showing work orders started, total daily production, and rejects; 2) yesterdays and accumulated yield by step, and projection of number of finished wafers from this quantity; 3) location of dormant work orders, i.e., orders that had not moved for a specified time; 4) current utilization of equipment and manpower; 5) number of orders awaiting processing at each step and how long they have been waiting; 6) daily operations schedule of wafers to be processed each day according to a predetermined priority structure; and 7) delivery forecast for when orders would be shipped and how the date varies according to resources applied. The inventory status data were structured in GPSS/360 to provide a common data format for both current status and forecasting. This fully operational system was developed to satisfy specific solid-state management requirements. This system was organized in a general manner for flexibility and change and could be modified to be used as a management information system for other types of operations.

Languages for Simulation

Simulation languages are past adolescence and nearing maturity. This is seen in the two papers in this session that describe improved and extended versions of the widely-used simulation languages GPSS and GASP, and by the papers that bring linguistics and mathematics to bear in providing more useful and usable simulation tools.

Cost Effectiveness Modeling Applied to Integrated Circuits

A computer logic model has been used to anticipate the functioning of an electronic system over its complete life span. Performance, cost, and availability comparisons were made between an existing equipment, Conalog, and redesigns using advanced microcircuit techniques. Results from the model indicated reductions in: cost of ownership by one-third, number of failures to one-tenth, and skill level of maintenance. Ten years of system operation were simulated using the IBM GPSS language in two minutes of IBM 7094 II time.