154 lines
4.3 KiB
Java
154 lines
4.3 KiB
Java
//******************************************************************************
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//
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// File: Simulation.java
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// Package: edu.rit.sim
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// Unit: Class edu.rit.sim.Simulation
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//
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// This Java source file is copyright (C) 2014 by Alan Kaminsky. All rights
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// reserved. For further information, contact the author, Alan Kaminsky, at
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// ark@cs.rit.edu.
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//
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// This Java source file is part of the Parallel Java 2 Library ("PJ2"). PJ2 is
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// free software; you can redistribute it and/or modify it under the terms of
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// the GNU General Public License as published by the Free Software Foundation;
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// either version 3 of the License, or (at your option) any later version.
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//
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// PJ2 is distributed in the hope that it will be useful, but WITHOUT ANY
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// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
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// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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//
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// A copy of the GNU General Public License is provided in the file gpl.txt. You
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// may also obtain a copy of the GNU General Public License on the World Wide
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// Web at http://www.gnu.org/licenses/gpl.html.
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//
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//******************************************************************************
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package edu.rit.sim;
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import edu.rit.util.PriorityQueue;
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/**
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* Class Simulation provides a discrete event simulation. To write a discrete
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* event simulation program:
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* <OL TYPE=1>
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* <P><LI>
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* Create a Simulation object.
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* <P><LI>
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* Create one or more {@linkplain Event}s and add them to the simulation (by
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* calling the {@link #doAt(double,Event) doAt()} or {@link
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* #doAfter(double,Event) doAfter()} methods).
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* <P><LI>
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* Run the simulation (by calling the {@link #run() run()} method). The
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* simulation performs events, by calling each event's {@link Event#perform()
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* perform()} method, in order according to the events' simulation times, as
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* returned by each event's {@link Event#time() time()} method. Performing an
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* event may cause further events to be created and added to the simulation.
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* <P><LI>
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* When there are no more events, the simulation is finished. At this point the
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* simulation's {@link #run() run()} method returns.
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* </OL>
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*
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* @author Alan Kaminsky
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* @version 12-Apr-2014
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*/
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public class Simulation
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{
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// Hidden data members.
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// Minimum-priority queue of events.
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private PriorityQueue<Event> queue = new PriorityQueue<Event>();
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// Simulation time.
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private double T = 0.0;
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// Exported constructors.
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/**
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* Construct a new simulation.
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*/
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public Simulation()
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{
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}
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// Exported operations.
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/**
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* Returns the current simulation time.
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*
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* @return Simulation time.
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*/
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public double time()
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{
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return T;
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}
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/**
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* Schedule the given event to be performed at the given time in this
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* simulation.
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*
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* @param t Simulation time for <TT>event</TT>.
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* @param event Event to be performed.
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*
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* @exception IllegalArgumentException
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* (unchecked exception) Thrown if <TT>t</TT> is less than the current
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* simulation time.
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* @exception NullPointerException
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* (unchecked exception) Thrown if <TT>event</TT> is null.
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*/
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public void doAt
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(double t,
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Event event)
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{
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if (t < T)
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{
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throw new IllegalArgumentException
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("Simulation.doAt(): t = "+t+" less than simulation time ="+T+
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", illegal");
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}
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if (event == null)
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{
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throw new NullPointerException
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("Simulation.doAt(): event = null");
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}
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event.sim = this;
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event.time = t;
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queue.add (event);
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}
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/**
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* Schedule the given event to be performed at a time <TT>dt</TT> in the
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* future (at current simulation time + <TT>dt</TT>) in this simulation.
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*
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* @param dt Simulation time delta for <TT>event</TT>.
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* @param event Event to be performed.
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*
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* @exception IllegalArgumentException
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* (unchecked exception) Thrown if <TT>dt</TT> is less than zero.
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* @exception NullPointerException
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* (unchecked exception) Thrown if <TT>event</TT> is null.
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*/
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public void doAfter
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(double dt,
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Event event)
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{
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doAt (T + dt, event);
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}
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/**
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* Run the simulation. At the start of the simulation, the simulation time
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* is 0. The <TT>run()</TT> method returns when there are no more events.
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*/
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public void run()
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{
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while (! queue.isEmpty())
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{
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Event event = queue.remove();
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T = event.time;
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event.perform();
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}
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}
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}
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