Transcript OR 335 - George Mason University
OR 335 / SYST 335
Introduction to ARENA
Introduction
Brant Horio [email protected]
Back to the Basics
Fundamentals of simulation methodology are the cornerstone of all simulation packages Basics are necessary for accurate model development and model output understanding Different packages then become only an issue of a new syntax
Model Development is an Art!
Incredible model flexibility with ‘over the counter’ simulation software packages Art of practice involved with interpretation of system Endless possibilities in ‘how’ to model a specific system
Model Development is an Art!
Essential Core of Simulation Analysis is Scientific Experimentation
Endless possibilities in ‘How’ to model a specific system You must determine best way to account for all relevant assumptions/variables and maintain end-user flexibility Maintain focus on problem as a whole
The Modeling Breakdown
10%:
Model Development
90%:
Problem Definition Data Collection / Analysis Scenario Experimentation Output Analysis Expected Success Measures Model Presentation
Success Story?
Aircraft Service Equipment Inventory Increase Is the increase necessary?
Is the expected service time improvement worth the associated massive capital expense?
These are questions Simulation Analysis is meant to answer
Success!
1 Simulation software license: Time to build model: Number of models built: Result: $18,000 3 months 1______ Priceless?
Nope, … Prevented capital expenditure of
~ $1 million
Introduction to ARENA
Windows driven interface Flowchart style model development Process blocks Process routing determined by connections between blocks Templates contain process blocks Example model construction of a One-Node system
Example One-Node System
Model is composed of 3 parts Creation/Introduction of entities to system Processing of entities in the system Exiting the entities from the system
Example Problem
The Sooty Dilemma
The Sooty Dilemma
CREATE: 43 new baby guinea pigs to be born at a rate of Triangular( 2, 5, 6 ) PROCESS: Baby guinea pigs are adopted at a rate of Triangular( 3, 5, 8 ) Question: What is the expected time for the entire litter to be adopted?
Note:
Distributions are unreasonable Assumptions of introduction of baby guinea pigs to system are inaccurate Emphasizes the point that:
GARBAGE IN, GARBAGE OUT!
Be Careful !!!
Basic Process
Template
Create
: Generate entities to system
Process
: Perform action on entities
Decide
: Routes entity based on condition
Dispose
: Exits entity from system
Additional Templates
CREATE
Module
Name
: Module name
Entity Type
: Unit to create for system
Time Between Arrivals
: Apply distribution or custom expression
Entities per Arrival
,
Max
and
First Creation
Spreadsheet Entry Available
Module parameter entry Flowchart view ( Double-click module block ) Selection of module block also opens specific spreadsheet view on bottom of screen
Spreadsheet Modules
Spreadsheet displays based on template Create and manage model components in centralized area
When in Doubt, Right Click
‘Build Expression’ provides flexibility Most useful for applying distributions Generate random numbers Create custom formulas
PROCESS
Module
Action:
Delay:
dd
Seize Delay:
dd
Seize Delay Release:
dd
Delay Release:
sds
PROCESS Module ‘Action’ Options
Delay
: Delays/Processes entity for a given time period ( No Queue )
Seize Delay ( Part 1 )
: Utilizes resource to process entity ( Queue )
Delay Release ( Part 2 )
: Utilizes captured resource to process, then releases resource
Seize Delay Release
: Utilizes resource to process entity, then allows resource to process another entity ( Queue )
PROCESS Module - Queues
Queues are customizable ( Dbl Click Queue )
DISPOSE
Module
Exits entity from system Automatically tracks entity throughput
Run Setup
Model Run
Remember time units!!!
General rule of thumb for replication is 30 Model will have automatic basic animations After run completion; report generation
Output Reports
Category by Replication Most data output is automatic Litter to be completely adopted in 272 days based on current assumptions!
ANIMATION!
Focus on basics for now Power of simulation is best embodied by its ability to communicate and justify recommendations to decision makers ‘Buy Off’ is of critical importance Animation is invaluable in assisting communication of the model May also act as a debugging tool
ANIMATION
Entity animation pictures are customizable under EDIT / ENTITY PICTURES Resource animation pictures are customizable through the ‘Animate’ button
Happy Modeling
Play around with Arena on your own Increased familiarity = increased model development proficiency