AnyLogic and Java

Nathaniel Osgood
 Advantages of AnyLogic
(as compared to other Agent-Based Modeling Software)

• Primarily declarative specification

• Less code
• Great flexibility
• Access to Java libraries
• Support for multiple modeling types
• Support for mixture of modeling types
 Painful Sides of AnyLogic Education/Advanced

• Export of model results: Lack of trajectory files

• Lack of a built-in debugger
• Need for bits of Java code
• Many pieces of system
Internals of AnyLogic files: XML
 Java Code: When & How Much?
• “Java” is a popular cross-platform “object oriented”
programming language introduced by Sun
Microsystems
• Anylogic is written in Java and turns models into Java
• AnyLogic offers lots of ways to insert snippets (“hooks”)
of Java code
• You will need these if you want to e.g.
– Push AnyLogic outside the envelop of its typical support
• e.g. Enabling a network with diverse Agent types
– Exchange messages between Agents
– Put into place particular initialization mechanisms
– Collect custom statistics over the population
 Stages of the Anylogic Build
Modification Modification Not Possible
Possible JVM
Java Code Byte
Code

Person.class
 Inspecting the Java code
• As a step towards creating an executable
representation of the code, AnyLogic creates a Java
representation
– If you want to see the Java code for a model, you will
need to do a “build”
• Sometimes it can be helpful to look at this Java code
– To find errors about which AnyLogic may be complaining
– Advanced: To see how things are being accomplished or
“work”
Requesting Viewing of Java Code
 Examples of Where to Insert Code
Object Properties
• “Advanced”
 Examples of Where to Insert Code
Object Properties
• “General”
 Example of Where to Insert Code
Presentations Properties
• “Dynamic”
properties of
presentation
elements
(especially
of Agents)
Tips to Bear in Mind While Writing Code
• Click on the “light bulb” next to fields to get
contextual advice (e.g. on the variables that are
available from context
• While typing code, can hold down the Control key
and press the “Space” key to request
autocompletion
– This can help know what parameters are required for a
method, etc.
• Java is case sensitive!
• Can press “Control-J” to go to the point in Java
code associated with the current code snippet
• Can press “build” button after writing snippet to
increase confidence that code is understood
Example of Contextual Information
Autocompletion Info (via Control-Space)
 Finding the Enclosing “Main” class
from an Embedded Agent
• From within an embedded Agent, one can find
the enclosing “Main” class by calling get_Main()
– This will give a reference to the single instance
(object) of the Main class in which the agent is
embedded
– An alternative approach is to call ((Main) getOwner)
 Presentation Properties
• Both key customizable classes (“Main”, various
Agent classes) can be associated with
“Presentation” elements
• These elements are assembled during execution
into animations & presentations of the agents
• Many of these presentation elements have
properties that can be set to Java expressions
Enabling Programmatic Control
 Getting to the AnyLogic Help
• Choose “Help”/”Help Contents”
• AnyLogic help includes many components
– Tutorials
– User references
– AnyLogic “library” information
Getting Information on the Anylogic (Java)
Libraries
 The Notion of a Code “Library”
• A “library” lets third parties (e.g. xjtek) share
compiled code they have developed with others
• The classes built into our AnyLogic projects (e.g.
Agent, ActiveObject, NetworkResourcePool, etc.)
are contained in the library
• The available libraries that come with AnyLogic &
Java have many additional components that can
offer tremendous additional functionality
– By tapping into this functionality, we can avoid having to
write code ourselves
• To use a library, you need to know what is in it!
 Finding out Information
Interfaces for Library Elements 1
 Finding out Information
Interfaces for Library Elements 2
 Using Libraries
• There are two major libraries that are “built
in” and can be used without additional
reference: Java libraries & AnyLogic libraries
• To use an object in the Java libraries, you will
use an “import” statement
 Using External Libraries
• There are tremendous numbers of 3rd party
libraries available for Java
• The functionality associated with these libraries
is incredibly diverse
• Many of these libraries are available for free;
others are sold
• It is very easy to make use of the functionality of
3rd party libraries from AnyLogic
– In order to do this, AnyLogic needs to “know about”
the external library.
Adding External Libraries 1
Adding External Libraries 2
Common Contextual Variables that are
Used by Code Snippets
• In statistics: “item” indicates current agent
• In “On Message Received” handler for agent:
“msg” indicates received message
• In Dynamic properties of an Agent’s replicated
line property: “index” indicates current
person’s index
• In “Parameters” properties of Agent
populations (used to set properties of agents
within population): “index” indicates the
index of the current agent in the population
 Example code to Export Dataset
FileOutputStream fos = new
FileOutputStream(“Filename”);
PrintStream p = new PrintStream(fos);
p.println(datasetName.toString()); // outputs
comma delimited values
 Useful Bits of Java Code
• get_Main() gets reference to Main object
• ActiveObject.trace(str) outputs string to log
• Engine.getTime() gets the current time
• agents.size() gets number of objects in collection
agents
• agents.item(i) gets item i from agent collection
• uniform() generates a random number from 0..1
 Useful Bits of Java Code : General
Expressions
• ActiveObject.traceln(Stringstr) outputs string to log
• time() gets the current internal model time (different
from the time in the external world)
• Members of com.xj.anylogic.engine.Utilities
– uniform() generates a random number from 0..1
– uniform(x) gen. a random number in range 0 to x
– lognormal(double meanNormal, double sigmaStdDevNormal,
double minNormal) draws from a lognormal distribution
– normal(double meanNormal, double sigmaStdDevNormal)
draws from a normal distribution
– Many other probability distributions
Methods on Populations of Agents (in
Main class)
• population.size() gets number of objects in
collection population
• population.statName() retrieves the current value of
the population statistic statName, as computed for
population population.
• population.item(int i) gets item i from population
collection
• add_populationname() Adds agent to that
population
• remove_populationname() Removes agent from that
population
 Useful Java Code: Methods to Call on
(or from within, using “this”) an Agent
• a.getConnectionsNumber() returns number of
connections between this agent and others
• get_Main() gets reference to Main object
• toString() gets string rendition of agent
• a.getConnections() gets a collection (linked) list of agents
to which this agent is connected (& over which we can
iterate)
• a.connectTo(Agent b) connects a to b
• a.disconnectFrom(Agent b) disconnects b from a
• a.disconnectFromAll() disconnects all agents from a
• a.getConnectedAgent(int i) gets the ith agent connected
to a
• a.isConnectedTo(Agent b) indicates if a is connected to b
 Methods on Statecharts
(Called from within Agent code)
• isStateActive(intstatename) indicates whether
agent is in a given state (composite or simple)
• getActiveSimpleState() Get number of simple
state. Can then compare to different state
names, e.g. in switch statement.
 Methods on Process Flow Diagrams
• source.inject(int count) injects a count of
entities into the source object (i.e. into an
object of type Source)
 Gotchas
• Changing rates for leaving a state do not get
updated until leave & reenter state (including
by a self-transition)
Example Use of getActiveSimpleState
switch (TBProgressionStatechart.getActiveSimpleState())
{
case LTBI:
return Color.YELLOW;
case UnDiagnosedActiveTB:
return Color.RED;
case DiagnosedActiveTB:
return Color.ORANGE;
case TBSusceptible:
default:
return Color.BLACK;
}
 Useful Snippets: Handling Messages
• Sending
– sender.deliver(msg, receiver) immediately deliver a
message from sender to receiver
– sender.send(msg, receiver) deliver a message from sender
to receiver
– environment.deliverToRandom(msg) [within Main]
immediately deliver a message to a random agent in the
environment
– send( "Infection", RANDOM_CONNECTED) [within an agent]
send a message to a randomly selected agent connected to
this one (where those agents are selected w/uniform prob)
• Receive message
– TBProgressionStatechart.receiveMessage( msg) to forward
message received by agent to statechart
 Useful Snippets
• Fields of dynamic properties of line object for
Agent Presentation (Under “Dynamic” tab of line’s
properties)
– Replication: getConnectionsNumber()
– dX: getConnectedAgent(index).getX() - getX()
– dY: getConnectedAgent(index).getY() - getY()
– These basically allow for appropriate initiation of visual
properties of the inter-agent connections
• In Agent’s “On Message Received” Handler (Under “Agent”
tab of Person)
• statechartname.receiveMessage( msg )
• This forwards a message received by this agent to statechart; note
that if there are different messages, destined for different
statecharts, they can be dispatched here to different targets