Introduction to simulation

The purpose of this tutorial is to introduce the basic concepts of discrete simulation as a decision making aide. The advantages and disadvantages of simulation are discussed as well as the basic steps in the simulation process. Factors to be considered as well as pitfalls to avoid are presented. 1 WHAT IS SIMULATION Simulation is one of the most powerful analysis tools available to those responsible for the design and operation of complex processes or systems. In an increasingly competitive world, simulation has become a very powerful tool for the planning, design, and control of complex systems. No longer regarded as the approach of “last resort” it is today viewed as an indispensable problem solving methodology for engineers, designers and managers. To simulate, according to Webster’s Collegiate Dictionary, is “to feign, to obtain the essence of, without the reality.” Thus according to Schriber [198’71, “Simulation involves the modeling of a process or system in such a way that the model mimics the response of the actual system to events that take place over time.” We will define Simulation as the process of designing a model of a real system and conducting expen”ments with this model for the purpose of either understanding the behavior of the system and/or evaluating various strate~-es for the operation of the system. We consider simulation to include both the construction of the model and the experimental use of the model for studying a problem. Thus, we ean think of simulation modeling as an experimental and applied methodology which seeks tcx * Describe the behavior of systems. * Construct theories or hypothesis that account for the observed behavior. * Use the model to predict future behavior, that is, the effects that will be produced by changes in the system or in its method of operation. 2 WHAT CAN BE SIMULATED ? In every research study on the utility and use of operations research techniques [Shannon et al 1981, Ford et al 1987], simulation has always turned up either first or second. The reason is its great versatility, flexibtity and power. When considering the question of what kinds of systems can be simulated, the answer is that almost any type has or can be studied. The broad range of applications of this methodology is almost impossible to classify. Rather than try to give an exhaustive list, we will simply try to point out some representative areas of previous applications. COMPUTER SYSTEMS hardware components, software systems, networks of hardware, data base structure and management, information processing, reliability of hardware and software, etc.. MANUFACTURING material handling systems, assembly lines, automated production facilities, automated storage facilities, inventory control systems, reliability and maintenance studies, plant layout, machine design, etc.. BUSINESS stock and commodhy analysis, pricing policy, marketing strategies, acquisition studies, cash flow analysis, forecasting, transportation alternatives, manpower planning etc.. GOVERNMENT military weapons and their use, mititary tactic-s, population forecasting, kmd use, health are delivery, f~e protection, police services, criminal justice, roadway design, traffic control, sanitation