sim/engine

This package holds the simulation core, consisting of the primary simulation
object (SimState), the schedule, and various utility objects which make
scheduling more convenient.


SimState.java

The top-level simulation object.  All elements of your model (excepting
visualization elements) will hang off of this object in one way or another.
This object can be serialized to disk to 'freeze dry' your entire simulation,
and unserialized to 'unfreeze' the simulation after you've moved it to,
for example, another computer.


MakesSimState.java 

A simple interface for objects which are capable of creating SimState
simulation models.  Largely used by the visualization toolkit: it's rare
that you'd need to use this.


Schedule.java

The representation of time in the simulation.  A discrete-event scheduler
on which you can schedule 'agents' (subclasses of Steppable) to be pulsed
at a future point in time, either once or repeatedly.


Steppable.java

An 'agent' in the simulation.  Subclasses of Steppable can be scheduled
on the schedule to have their 'step' methods called at future points in time.


Stoppable.java

Some agents can be scheduled to be stepped repeatedly for an indefinite
number of times in the future.  When this happens you'll be handed a
Stoppable object which enables you to stop an agent from being stepped
any more.


Sequence.java

A Steppable which holds an array of Steppables.  When the Sequence is
stepped, it iterates through this array and stepps each of the subsidiary
Steppables in turn.  You can add to, remove from, replace, and extend
this array if necessary.


RandomSequence.java

A Sequence which shuffles its array prior to iterating through it.


ParallelSequence.java

A Sequence which steps each of the Steppables in its array simultaneously
in separate threads, then waits for them to all complete.


MultiStep.java

A Steppable which holds a single subsidiary Steppable.  When stepped,
MultiStep either steps its subsidiary N times, or steps it only every
Nth time the MultiStep is stepped.


TentativeStep.java

A Steppable which holds a single subsidiary Steppable.  Prior to being
stepped, you can call stop() on the TentativeStep, which prevents it from
ever stepping its subsidiary.


WeakStep.java

A Steppable which holds a single subsidiary Steppable.  The subsidiary is
held as a weak reference, so it's free to be garbage collected if necessary,
in which case it's never stepped (of course).


AsynchronousSteppable.java

A Steppable which holds a single subsidiary Steppable.  When stepped, the
AsynchronousSteppable fires off a new thread in which the subsidiary is
stepped.  The AsynchronousSteppable doesn't wait for the subsidiary to
complete but rather immediately returns.  Options are available to block and
wait for the subsidiary to complete, among other things.
