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

Animation 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