Introduction to Simulation WS01/02 - L 04 1/40 Graham Horton
Discrete-Event
Simulation
14.11.2001
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Guidelines and tips
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Discrete Event Simulation, Essays (university) of Mathematical Modeling and Simulation
The paper emphasized directly on system events with a presentation of non-program flow charts but representations of system structure that may be used as a preliminary step in simulation model development;
Typology: Essays (university)
2016/2017
1 / 40
This page cannot be seen from the preview
Don't miss anything!
Related documents
Partial preview of the text
Download Discrete Event Simulation and more Essays (university) Mathematical Modeling and Simulation in PDF only on Docsity!
1/
Discrete-Event
Simulation
2/
Contents
- Models and some modelling terminology• How a discrete-event simulation works• The classic example - the queue in the bank• Example for a discrete-event simulation
4/
Advantages of Simulation
- Simulation has many advantages:
- study new designs without interrupting real system– study new designs without needing extra resources– Improve understanding of system– Manipulate time– Less dangerous / expensive / intrusive
5/
Model
- A model:
- is a set of assumptions about the operation of the
system
- These assumptions can be:
- algorithmic
(sequence of steps)
- mathematical
(equations)
- logical
(conditions)
- This model can be "run" in order to study the real
system
7/
Systems
System environment
A group of objectsthat interact
System
System
boundary
Placing the system boundary is the first difficult task inmodelling
8/
Example: Modelling a bank:
System environment
System
System
boundary
Customers
Cashiers
Special events Time of day
Systems
10/
Entities, Attributes & Activities
An entity is an object of interest in the systemAn attribute is a (relevant) property of an entity
customer
manager
cashier
account balance
gender
skills
Attributes are state variables
11/
Activities & Delays
An activity...
... is a duration of known length
check balance
drink coffee
serve customer
Activities form part of the model specificationA delay...
... is a duration of unknown length
Waiting time in queue Delays form part of the simulation result
13/
Events
An event...
Customerarrives fromoutside
Managerwakes up
... is an occurrence which
- is instantaneous• may change the state of the system
Service iscompleted
14/
Steps in a Simulation Study
Problemformulation
Set objectivesand plan
Conceptualmodel
Collectdata Create simulationmodel
Experimentaldesign
Productionruns & analysis
Documentation& report
Validation
Verification
16/
Input-Output Transformation
- View the (real or simulated) system as a "black box"
System
Inputvariables
Outputvariables
- Black box transforms input variables into output variables• Input variables are obtained by observing the real system• Output variables are obtained by observing the real system
and from the simulation experiment
17/
Model Specification
- Discrete-event modelling raises the following questions:• How does each event affect the system state and attributes?• How are activities defined?
- What events mark the beginning and the end?• What conditions (if any) must hold?
- How are delays defined?• How must the simulation be initialised?
- What events mark the beginning and the end?• What conditions (if any) must hold?
19/
- One possible problem formulation:
- "Customers have to wait too long in my bank"
- A typical objective:
- Determine the effect of an additional cashier on the
- A typical objective:
- "Customers have to wait too long in my bank"
mean queue length
- Data needed:
- Inter-arrival times of customers– Service times
A Simulation Classic
20/
- A typical simulation result:NQ
T
6 5 4 3 2 1 0