CS 450 Modelling and Simulation Dr. X

Topics Time Discrete and Continuous Simulation Simulation Design Process

Simulation Accuracy Can it ever be perfect? When is it good enough?

Coin Toss Simulation

Time Time is nature’s way of keeping everything from happening all at once. -Anonymous

Time in Simulations Core of everything that happens Events are anchored by when they occur Independent variable that exists in ALL simulations

Event Timeline

Time in Simulations AnimationAnimation Timeline

Continuous Simulations Examples: – Physical processes – Chemical Processes How to: – Use mathematical functions – Convert analog to digital Sample rate Visualization

Discrete Simulations Distinct, identifiable events Events occur at specific times Time in between does not interest us Example: queuing models, tetris

When Discrete Becomes Continuous

Hybrid Simulations

How to simulate time Sequencing Set Data Collection Events Continuous State Evaluation Animation timeline

States and Events

Simulation Design: what is important? Can we include all the details of a real system? How do we decide what is important?

Needs Analysis Performance gap in training simulation – Scale – Risk – Complexity – Product Design

Needs Analysis When is simulation not appropriate? – Simple technology would work as well or better – Not enough data – Real life activity is less expensive, not dangerous – Incomplete understanding of the system – Uncertain objectives

Step-Wise Refinement 1.Original System 2.Observable Elements 3.Conceptual Model 4.Operational Model 5.Computer Implementation

Step-Wise Refinement

The OR Approach 1. Problem formulation 2. Construction of the model 3. Model validation 4. Using the model, evaluate various available alternatives (solution) 5. Implementation and maintenance of the solution

Fill the table Original System System Activities Observable Elements Obtainable Data Simulation Events Simulation Input Data Collectible Data Traffic Intersection Computer Network NY City under the attack of Vampires Ebola virus in Africa

References The Guide to Computer Simulations and Games, By Katrin Becker and J.R.Parker, Wiley (Chapter 5) Computer Simulation Techniques: The Definitive Introduction, by Harry Perros, CS 45024