WSC` 12 Preparing Manuscripts
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1. An event oriented model is more efficient than a process oriented model because it minimises the number of active processes and avoids context switching However it is easier to follow complex model logic in a process oriented model In many such models it is the model s methods themselves that limit execution speed rather than the overhead of managing threads The best approach is to use an event oriented style the scheduleProcess method whenever possible and save the process oriented style the scheduleWait method for the more complex parts of the model Often it is useful to prototype new ob jects using scheduleWait methods and then after it works correctly optimize selected portions by con verting the code to use scheduleProcess When writing complex simulation models it is often necessary to interrupt a previously scheduled event and execute it immediately or to cancel it altogether The Entity methods for these functions are given in Table 4 Table 4 Interrupting and Terminating a Process Method Description getProcess Returns the active process executing the method The methods inter ruptProcess and killProcess are the only ones that require a process to be identified interruptProcess process Interrupts the given process and causes its next event to be executed im mediately killProcess process Interrupts the given process and terminates it With these few classes and methods discrete event simulat2. built in palettes of objects are provided in the Model Builder e Graphics components 2D and 3D components such as maps structures graphs text and model outputs 2D Overlay Graphics 2D components that appear in a fixed position in a View window Probability Distributions standard probability distributions and user defined distributions Basic Process Flow Components queue server source sink conveyor etc Mathematics and Control System Components integration addition PID controller etc Fluid Flow Components tanks pipes pumps fluids etc We frequently create new palettes of objects to support our modeling projects many of which are added to JaamSim More information on object palettes and the GUI can be found in the JaamSim User Manual 3 MODEL INPUTS AND OUTPUTS There is no question that the easiest and fastest way to build a simple model is to drag and drop the indi vidual objects and use the Input Editor to set their parameters However this method because less attrac tive for more complex models where the graphics become cluttered and the inputs very numerous For a really large model containing hundreds of objects it is usually necessary to build the model through an input file Sometimes a hybrid approach works best assemble the basic objects and graphical presenta tion using the GUI and then add more detailed inputs and additional objects using the input file Either way the only practical wa
3. 0 graphics card The JaamSim renderer was designed to operate independently from the simulation logic so that its ef fect on execution speed is as small as possible Each 3D window runs on a separate thread and interacts with the simulation only when it gathers the relevant information on the simulation state at the start of each rendering cycle The reduction in execution speed caused by opening one or more graphics win dows is only about 10 20 in most cases We often use a video clip to demonstrate the level of detail and quality of our simulation models to our clients To make video clip preparation more efficient this capability has been built directly into JaamSim Video content is captured off screen and to any specified resolution independent of what is shown on the computer monitor A capture rate of 10 frames per second is typically achieved at 1080p resolution At this speed a 3 minute video clip can be captured in less than 10 minutes 6 DISCRETE EVENT SIMULATION We now give a brief description of the JaamSim simulation engine that is intended to provide the reader with enough information to understand our approach and the engine s capabilities Table 1 lists the basic object classes that were created to implement the discrete event logic within Java King and Harrison Table 1 Basic Simulation Objects Object Description Simulation The overall simulation model Controls reading of input data s
4. Proceedings of the 2013 Winter Simulation Conference R Pasupathy S H Kim A Tolk R Hill and M E Kuhl eds OPEN SOURCE SIMULATION SOFTWARE JAAMSIM D H King Harvey S Harrison Ausenco Ausenco 855 Homer Street 855 Homer Street Vancouver BC V6B 2W2 CANADA Vancouver BC V6B 2W2 CANADA ABSTRACT JaamSim is a free open source simulation package written in the Java programming language A modern graphical user interface is provided that is comparable to commercial software including drag and drop model building an Input Editor Output Viewer and 3D graphics Users are able to create their own pal ettes of high level objects using standard Java and modern programming tools such as Eclipse If you are writing hundreds or thousands of lines of code in a proprietary programming language provided with your commercial software you would be far better off to write your code in Java and use JaamSim 1 INTRODUCTION This paper introduces JaamSim a free open source simulation package developed by the Ausenco a global engineering company JaamSim is aimed at a broad audience of professionals researchers and students and includes a modern graphical user interface GUI that is comparable to those provided by commercial off the shelf simulation software The software is written in the Java programming language and can be downloaded from Github The executable user manual programming manual and examples are available from th
5. TION SUM INPUTS AccelerationSum Controller Controller 1 AccelerationSum SequenceNumber 3 AccelerationSum InputValueList PositionIntegrator VelocityIntegrator AccelerationSum CoefficientList 0 2 0 01 The first three input lines define the Controller two Integrators and a WeightedSum object that cal culates the acceleration based on the present values for position and velocity and their coefficients corre sponding to the restoring and damping forces respectively The Controller object Controller 1 updates all the calculations and the SequenceNumber input determines the order in which each calculation is performed Although the graphics for this model appear to be two dimensional they are actually part of a three dimensional scene The objects are flat and lie in the x y plane These flat icons could be replaced by a 3D graphics if required 5 3D GRAPHICS JaamSim provides hardware accelerated 3D graphics through a built in rendering system that was written specifically for this application Graphics are displayed in real time and are fully interactive The user can pause the model at any time and query an Entity by clicking on its representation on the computer screen Model inputs and outputs can be checked using the Input Editor and the Output Viewer If necessary the values of all the internal variables of the Entity can be displayed using the Property View er If execution is resumed while these t
6. Tortuga Kuhl F The MITRE Corporation http code google com p tortugades YouTube channel for Ausenco Simulation http www youtube com user javasimulation AUTHOR BIOGRAPHIES HARRY KING is the Manager of the Simulation Department at Ausenco Ausenco is a full service en gineering company with a staff of approximately 3 500 people and head office in Brisbane Australia The Simulation department is based in Vancouver Canada and has a staff of 19 professionals Dr King holds a Ph D in Theoretical Physics from the University of Texas at Austin and has devoted his career to simulation modeling since 1979 His email address is harry king ausenco com HARVEY HARRISON is the Assistant Manager Software for the Simulation Department at Ausenco He was the lead programmer for the development of Ausenco s discrete event simulation software and has experience in many types of modeling including transportation demand models population change models vehicle micro simulation and toll revenue models He has an interest in systems programming and has many contributions to the Linux kernel His email address is harvey harrison ausenco com
7. ava Previous open source simulation engines in Java include CSIM DESMO J DEUS DSOL JavaSim JiST Jsim JSL SimJava Simkit SSJ and Tortuga However to the best of our knowledge JaamSim is the first to provide the modern GUI required for the software to have a wide appeal King and Harrison 2 INSTALLING AND USING JAAMSIM JaamSim is an extremely light weight application consisting of a single 10MB executable including all dependencies The executable can be copied directly to the user s computer No special installation pro gram is required JaamSim will run on most modern computers that support OpenGL graphics version 3 0 or later including laptop computers with Intel Core 15 and 17 series processors that rely on integrated graphics The graphical user interface GUD for JaamSim provides all the necessary tools for model building e Control Panel the main interface to JaamSim that controls the execution of models and provides access to the other GUI components Views one or more windows showing 3D views of the model universe Model Builder tool for dragging and dropping model components Object Selector provides access to each object in the model Input Editor displays the inputs to the selected object and permits editing Output Viewer displays the present value for the outputs from the selected object Property Viewer debugging tool that displays all the internal properties for the selected object A number of
8. e authors on request The key feature that makes JaamSim different from commercial off the shelf simulation software is that it promotes the development customized palettes of high level objects for new applications New ob jects automatically have 3D graphics can be dragged and dropped have their inputs editable through the Input Editor and their outputs displayed in the Output Viewer Programming is done in standard Java us ing modern development tools such as Eclipse Unlike commercial simulation software JaamSim is not restricted by the idiosyncrasies and limited feature set of a proprietary programming or scripting lan guage JaamSim was developed from Ausenco s Transportation Logistics Simulator TLS software that we use to model mine to port and port to port supply chain studies for the Mining and Oil amp Gas indus tries Everything in TLS that is generic in nature and not related to supply chains was transferred to JaamSim It includes all the discrete event logic input and output handling programming tools user interface 3D graphics and palettes of basic objects TLS became a collection of add on palettes for JaamSim containing objects for ships berths stockpiles railways etc A good way to assess the capabili ties of JaamSim is to view our TLS models on YouTube Apart from the specialized objects everything you see in these videos is available in JaamSim JaamSim is not the first open source simulation offering in J
9. iffers from a simple method call in that a new process is created allowing the method to be executed in parallel to the original method rather than in series scheduleProcess dur method argl arg2 The same function as startProcess except that the given method is called after the specified delay The new process is created at the end of the de lay minimizing the number of active processes Simulated time can be advanced using the Entity methods in Table 3 Table 3 Scheduled and Conditional Waits Method Description scheduleWait dur pri while condition waitUntil waitUntilEnded scheduleLast Stops the execution of the current method for the given duration in simu lated time Can be placed anywhere within a method and can be used multiple times within a method Code structure used to create conditional waits Two methods waitUntilQ and waitUntilEnded are used Stops execution of the current method un til the given condition is false Stops execution of the current method until all other events scheduled for the present simulated time have been executed JaamSim allows both the process and event orientation to be used freely in the construction of a simulation model e scheduleWait is the key method for writing a process orientated simulation model e scheduleProcess is the key method for writing an event oriented simulation model King and Harrison
10. ion becomes a simple extension of the Java programming language 7 CREATING NEW OBJECTS AND PALETTES Our key motivation in creating JaamSim was to give the simulation modeling community an easy way to create new palettes of high level objects that can be used in their modeling projects To make use of this capability the modeler must have some basic programming skills but does not have to be an expert in this field If fact the code for the objects in the various palettes is extremely simple and does not require much knowledge of the GUI to understand A good example of model code is that for the Server object which can be found in the file com jaamsim BasicObjects Server java Two methods contain the core logic for the Server addEnti ty ent Y and processEntities The first method addEntity ent is called when the entity ent arrives at the Server and is passed to its Queue a separate object that is stored in the property queue If the Server is idle it is re started by calling the method processEntities The following lines of code implement this logic Add an entity from upstream ey public void addEntity Entity ent queue addLast ent if busy this startProcess processEntities This method illustrates the need to start a new Process in some circumstances In this case a new Process is started when processEntities is called Thi
11. ools are open the entries are updated automatically as events are executed The renderer uses the JOGL2 implementation of OpenGL graphics for Java It provides modern shader based graphics that runs efficiently on games type graphics cards There is no need to use the more expensive workstation type graphics cards normally required for engineering software 3D models can be imported to JaamSim from Collada files dae Complex graphical models are typically created using 3ds Max or Maya and converted to Collada format using the appropriate OpenCol lada plug in Engineering content created in AutoCAD can be imported directly by 3ds Max and convert ed in the same way One of the goals for the JaamSim renderer was that it be capable of displaying fully detailed engi neering content directly from the CAD software without the manual tuning or re working that is normally required to get an acceptable frame rate Figure 3 shows an example for two liquefied natural gas ships King and Harrison Ausencs Figure 3 Graphics Example The two ships are highly detailed with approximately 200 000 polygons in each object Complex graphical models such as these can be used freely in JaamSim while maintaining a frame rate of 60 frames per second fps with a games type graphics card We have stress tested JaamSim with a scene containing 50 million polygons A usable frame rate of approximately 10 fps was achieved for this scene using an Nvidia GTX68
12. provided whenever possible depending on the type of input 4 EXAMPLE MODEL Having discussed the basics of a JaamSim model it is appropriate to show a simple example The fol lowing model for a simple harmonic oscillator is one of the example models provided with JaamSim LL AE Position and Velocity Position m Velocity m s Acceleration Velocity Position 0 012 _0 012 m s2 0 319 m s 0 076 m amp 0 01 06 Ausenco Figure 2 Harmonic Oscillator Example King and Harrison In this example the variables position velocity and acceleration are updated every 0 01 seconds by the controller shown in the bottom left of the screen The key inputs used to create this model excluding graphics are given by the following entries in the input file DEFINITIONS Define Controller Controller 1 Define Integrator VelocityIntegrator PositionIntegrator Define WeightedSum AccelerationSum CONTROLLER INPUTS Controller 1 SamplingTime 0 01 s VELOCITY INTEGRATOR INPUTS VelocityIntegrator Controller Controller 1 VelocityIntegrator SequenceNumber 1 VelocityIntegrator InputValue AccelerationSum VelocityIntegrator InitialValue 0 POSITION INTEGRATOR INPUTS PositionIntegrator Controller Controller 1 PositionIntegrator SequenceNumber 2 PositionIntegrator InputValue VelocityIntegrator PositionIntegrator InitialValue 1 ACCELERA
13. s step is necessary because the processing of en tities by the Server must be performed in parallel with the process that called the addEntity ent X meth od If the code had read simply King and Harrison this processEntities the method that had called addEntity ent would not continue to the next line of code until proces sEntities had terminated This rule differs from many other simulation software packages that return control to the calling method as soon as a time delay is reached The second method processEnitites loops through the entities in the queue and processes them one by one The method terminates when all the queued entities have been processed and the Server is set to idle y k k Process entities from the Queue vi public void processEntities busy true while queue getCount gt 0 servedEntity queue removeFirst double dt serviceTimeDistribution nextValue this scheduleWait dt numberProcessedtt this getNextComponent addEntity servedEntity servedEntity null busy false The processEntities method demonstrates how time is advanced by the method sched uleWait dt Note that this method can appear in the middle of a method and within program structures such as loops allowing for more readable code The Server object is wired into the GUI by the following lines in the autoload cfg file tha
14. t is auto matically loaded when JaamSim is first launched Defin Palett Basic Objects Defin ObjectType Server Server JavaClass com jaamsim BasicObjects Server Server Palett Basic Objects Server DefaultDisplayModel Rectangle These inputs use the same format as a normal input file The first two lines define the palette Basic Ob jects and the object type Server The third line identifies the Server object type with the Server class in the Java code files The last two lines assign the Server to the Basic Objects palette and set its default appearance to that of a rectangle The autoload cfg file is used to create nearly all the objects in JaamSim Only a few high level in stances such as Simulation and EventManager are created in the Java code 8 CONCLUSIONS This article has introduced the JaamSim software and has provided an overview of many of its features We invite interested readers to contact the authors of this paper to obtain the user manuals examples and other documentation for the software At its present level of development JaamSim is suitable for any model builder who is willing to pro gram and who finds the present generation of simulation software ill suited for the intended application If you are writing hundreds or thousands of lines of code in a proprietary programming language provided with your commercial software you would be far better off to write
15. tarting of the simulation run termination of the simulation run and printing of output reports EventManager Maintains simulated time and the list of future and conditional events to be executed Entity The basic object for the simulation Can be permanent or temporary during the simula tion run and can be either active or passive in the model logic Process A sub class of thread that allows an entity to execute a series of methods in simulated time while other entities execute their own series of methods Note that we have separated the two objects Entity and Process When an Entity is playing an active role in the simulation it will have one or more Processes underway When it is playing an inactive role or is temporarily dormant it will have no Process underway Unlike most other simulation software we have made the distinction between starting a new method which is done in series with the original method and starting a new process which is done in parallel with the original method Other simulation languages return control to the original method if the called method is halted by a wait equivalent to starting a new process each time a method is called New processes can be created and started using the Entity methods in Table 2 Table 2 Starting a Process Method Description startProcess method arg arg2 Calls the given method with the specified arguments i e this method arg1 arg2 However it d
16. uire more sophisticated tools and the use of standard programming languages such as Java and C We hope that the introduction of JaamSim will be a useful step in that direction REFERENCES Ausenco http www ausenco com Cliffs of Dover IC Maddox Games http www cpublishing eu game il 2 sturmovik cliffs of dover overview CSIM Mesquite Software http www mesquite com DESMO J Page B University of Hamburg http desmoj sourceforge net home html DEUS Agosti M University of Parma http code google com p deus DSOL Verbraeck A Delft University of Technology http sk 3 tbm tudelft nl simulation index php GitHub website for Ausenco Simulation https github com AusencoSimulation JavaSim Little M C Newcastle University http javasim codehaus org JiST Barr R Cornell University JiST Java in Simulation Time User Guide http jist ece cornell edu JOGL2 Jogamp Community http jogamp org JSL Rossetti M D University of Arkansas http www uark edu rossetti research research_interests simulation java_simulation_library_js OpenCollada http opencollada org Rfactor2 Image Space Incorporated http www imagespaceinc com SimJava Howell F University of Edinburgh http www dcs ed ac uk home hase simjava Simkit Buss A Naval Postgraduate School USA http diana nps edu Simkit SSJ L Ecuyer P University of Montreal http www iro umontreal ca simardr ssj indexe html
17. y to ensure that the inputs to a large model are correct is to audit the input file line by line JaamSim allows models to be constructed either through the GUI or an input file The input file uses an object keyword value structure For example the following lines of input Define Ship LargeShip LargeShip Length 300 m would define the object LargeShip an instance of Ship and assign the value three hundred meters to its Length input Note that all model inputs are assigned units where appropriate and unit conversions are done automatically by the program Internal calculations are done in SI units by JaamSim The Input Editor uses the same object keyword value structure as the input file The following figure shows an example of the Input Editor King and Harrison ut Editor Queve 1 1 180684 0 045160 0 000000 m 0 0 0 0 0 5 Figure 1 Input Editor In this example the Input Editor was opened for the object Queue 1 which has its keywords orga nized into the categories Basic Graphics and Key Inputs The tooltip pop up shows the definition of the keyword Alignment and an example of its use Definitions are given in this way for all model in puts and outputs The software uses annotations to encode this material thereby making the program largely self documenting Model inputs are changed by clicking on the entry in the Value column and typing an new value Drop down menus are
18. your code in Java and use JaamSim Model builders who are unwilling to program should stay with commercial software for the time be ing However the number and variety of objects available in JaamSim will increase over time and even tually it may become an attractive alternative to commercial software for all users Ausenco will continue to improve JaamSim as we develop new features and enhancements for our proprietary TLS software Our goal in creating JaamSim is to propel the field of simulation beyond the restrictions of proprie tary simulation programming languages into the next generation of sophisticated and detailed models King and Harrison These models will begin to resemble video games in the level of detail that is modeled and in the quality of their graphics In fact the most sophisticated simulation models available today are not those being written by simulation professionals such as ourselves but by the video game companies who create flying and car racing games The best of these games such as Cliffs of Dover and Rfactor2 model the physics controls instrumentation and graphics to an order of magnitude greater detail than the best engi neering models It would not be possible to build engineering models to this level of detail using the pre sent generation of off the shelf simulation software The games industry has shown us what is possible To develop the next generation of engineering simulation models will req
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