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
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 System2. Observable Elements3. Conceptual Model4. Operational Model5. Computer Implementation
Step-Wise Refinement
Step-Wise Refinement
The OR Approach
1. Problem formulation2. Construction of the model3. Model validation4. 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 VampiresEbola virus in Africa
CS 450 24
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, http://www4.ncsu.edu/~hp/simulation.pdf