Page 248 - DCAP601_SIMULATION_AND_MODELING

Simulation and Modelling

Notes
!
Caution The use of the term bootstrapping can be contrasted with its use in both statistics
and computing.

Statistics
The simulation typically keeps track of the system’s statistics, which quantify the aspects of
interest. In the bank example, it is of interest to track the mean service times.

Ending Condition
Because events are bootstrapped, theoretically a discrete-event simulation could run forever. So
the simulation designer must decide when the simulation will end. Typical choices are “at time
t” or “after processing n number of events” or, more generally, “when statistical measure X
reaches the value x”.

Simulation Engine Logic
The main loop of a discrete-event simulation is something like this:

Start

1. Initialize Ending Condition to FALSE.
2. Initialize system state variables.
3. Initialize Clock (usually starts at simulation time zero).

4. Schedule an initial event (i.e., put some initial event into the Events List).
“Do loop” or “While loop”

While (Ending Condition is FALSE) then do the following:
1. Set clock to next event time.
2. Do next event and remove from the Events List.
3. Update statistics.

4. End
5. Generate statistical report.

Application Areas/Common Uses

Well-known examples of Simulation are Flight Simulators, Fleet Management and Business
games. However, there are a large number of potential areas for Discrete Event Simulation. One
of the main areas currently being explored is in designing new manufacturing areas, especially
where high capital investment is involved. For example, if a company wishes to build a new
production line, then the line can be first simulated to assess feasibility and efficiency. The
diagram below shows the key stages in using Discrete Event Simulation. It can be noted that this
bears a strong resemblance to other simulation techniques and other analysis program
development methodologies (prototype method) [Somerville, 1992].

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