umontreal.iro.lecuyer.simevents

Class Simulator

java.lang.Object

umontreal.iro.lecuyer.simevents.Simulator

Direct Known Subclasses:

ProcessSimulator

public class Simulator
extends java.lang.Object

Represents the executive of a discrete-event simulator. This class maintains a simulation clock, an event list, and starts executing the events in the appropriate order. Its methods permit one to start, stop, and (re)initialize the simulation, and read the simulation clock.

Usually, a simulation program uses a single simulation clock which is represented by an instance of this class. For more convenience and compatibility, this class therefore provides a mechanism to construct and return a default simulator which is used when an event is constructed without an explicit reference to a simulator, and when the simulator is accessed through the Sim class.

Note that this class is NOT thread-safe. Consequently, if a simulation program uses multiple threads, it should acquire a lock on a simulator (using a synchronized block) before accessing its state. Note however, that one can launch many simulations in parallel with as many threads, as long as each thread has its own Simulator.

Field Summary

Fields

Modifier and Type	Field and Description
static Simulator	defaultSimulator Represents the default simulator being used by the class Sim, and the no-argument constructor of Event.

Constructor Summary

Constructors

Constructor and Description
Simulator() Constructs a new simulator using a splay tree for the event list.
Simulator(EventList eventList) Constructs a new simulator using eventList for the event list.

Method Summary

Modifier and Type	Method and Description
ContinuousState	continuousState() Returns the current state of continuous variables being integrated during the simulation.
static Simulator	getDefaultSimulator() Returns the default simulator instance used by the deprecated class Sim.
EventList	getEventList() Gets the currently used event list.
void	init() Reinitializes the simulation executive by clearing up the event list, and resetting the simulation clock to zero.
void	init(EventList evlist) Same as init, but also chooses evlist as the event list to be used.
boolean	isSimulating() Determines if this simulator is currently running, i.e., executing scheduled events.
boolean	isStopped() Determines if this simulator was stopped by an event.
void	start() Starts the simulation executive.
void	stop() Tells the simulation executive to stop as soon as it takes control, and to return control to the program that called start.
double	time() Returns the current value of the simulation clock.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

defaultSimulator

public static Simulator defaultSimulator

Represents the default simulator being used by the class Sim, and the no-argument constructor of Event. This simulator is usually obtained with the getDefaultSimulator method, which initializes it if needed. But it might also be initialized differently, e.g., if process-driven simulation is required.

Constructor Detail

Simulator

public Simulator()

Constructs a new simulator using a splay tree for the event list.

Simulator

public Simulator(EventList eventList)

Constructs a new simulator using eventList for the event list.

Method Detail

time

public double time()

Returns the current value of the simulation clock.

Returns:

the current simulation time

init

public void init()

Reinitializes the simulation executive by clearing up the event list, and resetting the simulation clock to zero.

init

public void init(EventList evlist)

Same as init, but also chooses evlist as the event list to be used. For example, init (new DoublyLinked()) initializes the simulation with a doubly linked linear structure for the event list. To initialize the current Simulator with a not empty eventList is also possible, but the events scheduled in the eventList will be linked with the current simulator only.

Parameters:

evlist - selected event list implementation

getEventList

public EventList getEventList()

Gets the currently used event list.

Returns:

the currently used event list

isSimulating

public boolean isSimulating()

Determines if this simulator is currently running, i.e., executing scheduled events.

isStopped

public boolean isStopped()

Determines if this simulator was stopped by an event. The simulator may still be processing the event which has called the stop method; in this case, isSimulating returns true.

start

public void start()

Starts the simulation executive. There must be at least one Event in the event list when this method is called.

stop

public void stop()

Tells the simulation executive to stop as soon as it takes control, and to return control to the program that called start. This program will then continue executing from the instructions right after its call to start If an Event is currently executing (and this event has just called stop), the executive will take control when the event terminates its execution.

continuousState

public ContinuousState continuousState()

Returns the current state of continuous variables being integrated during the simulation. This state is used by the Continuous class when performing simulation of continuous variables; it defaults to an empty state, which is initialized only when this method is called.

Returns:

continuousState field

getDefaultSimulator

public static Simulator getDefaultSimulator()

Returns the default simulator instance used by the deprecated class Sim. If this simulator does not exist yet, it is constructed using the no-argument constructor of this class. One can specify a different default simulator by setting the defaultSimulator field directly.