Description about simulation softwares

1. Simulation
Software
DISCRETE-EVENT SYSTEM SIMULATION

3. Comparison of Simulation Packages with Programming
Languages

4. CLASSIFICATION OF SIMULATION
SOFTWARE
General-purpose vs. Application-Oriented packages
– Traditionally: simulation languages and simulators
Languages were flexible but required programming, simulators were easy to
use but not very flexible
– Now, almost all simulation software uses graphical interface so is relatively easy to
use and to learn
– Distinction now is between general-purpose simulation software and applications-
oriented package
Specific applications include manufacturing, call centers, telecommunications,
etc.

5. CLASSIFICATION OF SIMULATION
SOFTWARE
Modeling approaches
– Event-scheduling approach
Can uses general programming languages, or some simulation languages
During processing of an event, no simulated time passes
– Process-interaction approach
 Now used by most simulation software
 Instead of identifying events, identify entities (a.k.a. processes) that are created, flow around or through the
system
 May have multiple realizations of an entity/process
 May have different kinds of entities/processes
 “Program” consists of a description of what happens to the different kinds of processes (including their entry and
exit)
 Usually expressed graphically, like a flowchart
 During processing of an entity/process, simulated time usually passes

6. CLASSIFICATION OF SIMULATION
SOFTWARE
Common modeling elements
– Entities – represent customers, parts, messages, paperwork, airplane, etc.
– Attributes – Information stored with each entity
Usually, every individual entity has the same set of attributes, but the values differ
to distinguish the entities
Some attributes are automatic, others are user-defined and user-maintained
– Resources – servers, machines, workers, nodes,
links, runways, gates, agents, clerks, etc.
– Queues – where entities wait if resources are not
available

7. World Views of Simulation Model
Event-Scheduling View
◦ Focus on processing each event
Process-interaction View
◦ View model as a set of processes through which an entity “flows”
◦ Life-cycle approach – time-sequenced list of events, activities, & delays
◦ Common in simulation environments
Activity Scanning Approach
◦ Focus on activities & conditions that allow it to begin
◦ At each clock advance, scan conditions to start any activity that can begin
◦ Approach is simple, but scan is slow
◦ New 3-phase approach includes some event scheduling – somewhat more complex but
more efficient

8. Categories of Simulation Software
General Purpose Languages
◦ C, C++, Java
Simulation Languages
◦ GPSS, SIMAN, SLAM, SSF
Simulation Environments
◦ Enterprise Dynamics, Arena, SIMUL8

9. Features of Simulation Languages
Some focus on a single type of application
Built in features include
◦ Statistics collection
◦ Time management
◦ Queue management
◦ Event generation
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10. Features of Simulation Environments
Hardware and software requirements
– Matches platform/OS – Windows, UNIX, MacOS
Animation and dynamic graphics
– Concurrent vs. postprocessing
– 2D vs. 3D
– Import CAD drawings
– Display statistics, graphs dynamically during execution
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Some focus on one type of application
Icon based
Analysis of I/O
Advanced Statistics
Optimization
Support for Experimentation

11. DESIRABLE SOFTWARE FEATURES
General capabilities
– Modeling flexibility – ability to drill down to lower levels of programming,
create custom modeling constructs
– Ease of use
– Hierarchical modeling – submodels containing submodels, etc.
– Fast execution speed
– Ability to create user-friendly front/back ends for template creation
– Run-time version for wide distribution of model
– Import/export data from/to other applications
– Automatic execution of models for different input-parameter combinations
– Combined discrete/continuous modeling
– Ability to initialize in other than empty & idle
state
– Save state at end to re-start later
– Affordable

12. DESIRABLE SOFTWARE FEATURES
Statistical capabilities
– Adequate random-number generator for basic U(0, 1) variates
Statistical properties, cycle length, adequate streams and substreams
RNG seeds should have good defaults, be fixed – not dependent on clock
– Comprehensive list of input probability distributions
Continuous, discrete, empirical
– Ability to make independent replications
– Confidence-interval formation for output performance measures
– Experimental design
– Optimum-seeking
 • Customer support and documentation
 • Output reports and graphics
– Standard defaults, customizable – stored in
database for postprocessing

13. Evaluating Software
Consider multiple issues
◦ Ease of use, support, applicability
Speed of execution
◦ Experimental runs – Debugging
Beware of demos & advertising
◦ Will focus on strengths only
◦ Ask for demo of YOUR problem
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14. Evaluating Software
Carefully consider comparison checklists with yes/no answers
Can software link to external languages
Carefully consider trade-off between graphical model building
& simulation programming language
Costs – one-time vs. licensing
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15. GENERAL-PURPOSE SIMULATION
PACKAGES
• See text for discussion of two popular general-purpose
simulation packages – Arena and Extend
– In each, builds a model of a small manufacturing system
• Mentions some additional general-purpose simulation
packages
– AweSim, Micro Saint, GPSS/SLX, SIMPLE++, SIMUL8, Taylor
Enterprise Dynamics
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16. GPSS
General Purpose Simulation System
Highly Structured
Process Approach
Queuing Systems
Block Diagrams
40 standard blocks
Block corresponds to a statement
Transactions FLOW through the system
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17. Other Simulation Software
SSF – Scalable Simulation Framework
◦ Application Program Interface (API)
◦ Object-oriented, process view
◦ 5 Base Classes
Process, Entity, Event, InChannel, OutChannel
◦ Designed for high-performance computers
◦ Bridges pure Java & simulation languages
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18. Simulation Environments ~~
Common Features
GUI
Animation
Automatic statistics
Output (tables, graphs, custom)
Analysis
Process world view
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Some allow
Event Scheduling
Mixed continuous-discrete
models
Animations – 2D & 3D
Business Graphics

19. Simulation Environments
AnyLogic
Arena
AutoMod
Enterprise
Dynamics
ExtendSim
Flexsim
ProModel
SIMUL8
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20. AnyLogic
Supports: discrete event, agent-based, system dynamics (& combination)
Hybrid: discrete & continuous
Object library
Java models, publish as applets
Animation, Statistics, optimization, debugger
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21. Arena
Discrete & Continuous systems
Object-based; GUI
2D, 3D Animation
Business & Manufacturing processes
Supports Analysis
OptQuest for optimization
Based on SIMAN; embedded Visual Basic
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22. SIMSCRIPT
SIMSCRIPT, a general programming system specially adapted to the problems
of writing simulation programs. The advantages of SIMSCRIPT are that it
reduces the time needed to program simulations of even moderate complexity
and provides increased flexibility in modifying such models in accordance with
the findings of preliminary analysis and other circumstances.
The SIMSCRIPT programming system is especially designed to facilitate the
writing of simulation programs. Digital simulations generally consist of a
numerical description of "status", which is modified at various points in
simulated time called "events".
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23. AutoMod
Manufacturing & Materials handling
Detailed large models for planning, decision support, control
systems
AutoStat - Experimentation & analysis
AutoView - Make movies of 3D animations
Full simulation language included
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24. Object oriented
Discrete Events
Open GL 3D visualization engine
4D Script programming language
Interfaces with databases
OptQuest optimization
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25. ExtendSim
Block-diagram approach
Versions for mixed and for continuous only
Includes C-like programming language
Supports linking to external languages
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26. Flexsim
Dynamic-flow systems - manufacturing
Discrete-event, Object-oriented simulator; developed in C++ using Open GL
Animation: 2D, 3D, Virtual reality
Drag & Drop
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27. ProModel
Manufacturing Systems
Simulation & Animation (2D & 3D)
Output viewer – graphs, tables
SimRunner – optimizer based on evolutionary algorithm technique
OptQuest is also available
MedModel, ServiceModel
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28. SIMUL8
Service industries, transaction processing
Drop & Drag model development
Saves in XML format
Pre-built templates for common applications
3D virtual reality graphics
Links to database
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29. Experimentation & Statistical
Analysis Tools
Included in all most all simulation systems
Add-ons also available
Features
◦ Optimization – define fitness or cost function
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30. Arena
Output & Process Analyzer
Confidence intervals
Comparison of systems
Warm-up determinations
Graphs (all types) – 2D & 3D
Scenario definition
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31. AutoStat (from AutoMod)
Warm-up determination
Steady state determination
Confidence intervals
Sensitivity analysis
Optimization via evolutionary strategy
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32. OptQuest
Based on scatter search, tabu search, linear-integer programming, data
mining, neural nets (evolutionary)
Uncertainty problems
Global optimums
Handles non-linear and discontinuous relationships
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33. SimRunner (from ProModel)
Based evolutionary models & genetic algorithms
Optimizations
3D graphics
Warm-up (steady state) determination
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34. Conclusion
Many simulation software environments available
Many do have trial versions to download for trying
Before deciding, consider the features and the add-ons available that will
suit your particular environment
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35. GPSS Block Diagram for Example
Each entity has a name
Name each queue, server, etc.
In rectangle, parameters (as necessary)
Right attachment, name of entity
Far right column – GPSS Command
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36. GPSS Syntax
Assembly-like
Label OpCode Subfields ; comment
Label: col. 1, <= 9 alphanumeric, alpha start
OpCode: 4+ characters of command
Subfields: as necessary, separated by commas
Comment: after ; or with * in column 1
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37. GPSS Program
Declaration Section
Customized vs. Standard Output
Code Section
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38. 38
Generate rvexpo (1,&IAT)
Queue Systime
Queue Line
Seize Checkout
Depart Line
Advance rvnorm(1,&mean,&stdev)
Release Checkout
Depart Systime
Test_GE M1, 4, Term
Blet &Count = &Count +1
Ter Terminate 1
Start &Limit