001/* An actor that outputs a random sequence with a Exponential distribution.
002
003 Copyright (c) 2004-2016 The Regents of the University of California.
004 All rights reserved.
005 Permission is hereby granted, without written agreement and without
006 license or royalty fees, to use, copy, modify, and distribute this
007 software and its documentation for any purpose, provided that the above
008 copyright notice and the following two paragraphs appear in all copies
009 of this software.
010
011 IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
012 FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
013 ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
014 THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
015 SUCH DAMAGE.
016
017 THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
018 INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
019 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
020 PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
021 CALIFORNIA HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
022 ENHANCEMENTS, OR MODIFICATIONS.
023
024 PT_COPYRIGHT_VERSION_2
025 COPYRIGHTENDKEY
026
027 */
028package ptolemy.actor.lib.colt;
029
030import cern.jet.random.Exponential;
031import ptolemy.actor.parameters.PortParameter;
032import ptolemy.data.BooleanToken;
033import ptolemy.data.DoubleToken;
034import ptolemy.data.expr.SingletonParameter;
035import ptolemy.data.type.BaseType;
036import ptolemy.kernel.CompositeEntity;
037import ptolemy.kernel.util.IllegalActionException;
038import ptolemy.kernel.util.NameDuplicationException;
039
040///////////////////////////////////////////////////////////////////
041//// Exponential
042
043/**
044 Produce a random sequence with a Exponential distribution.  On each
045 iteration, a new random number is produced.  The output port is of
046 type DoubleToken.  The values that are generated are independent
047 and identically distributed with the lambda and the standard
048 deviation given by parameters.  In addition, the seed can be
049 specified as a parameter to control the sequence that is generated.
050
051 <p> This actor instantiates a
052 <a href="http://hoschek.home.cern.ch/hoschek/colt/V1.0.3/doc/cern/jet/random/Exponential.html">cern.jet.random.Exponential</a> object with
053 lambda set to 1.0.  The distribution is defined as
054 <pre>
055 p(x) = lambda*exp(-x*lambda) for x &ge; 0, lambda &gt; 0
056 </pre>
057 The above description of Exponential is
058 <a href="doc-files/colt-copyright.htm">copyrighted</a>.
059 Note that the mean is 1/lambda, and the standard deviation is 1/lambda^2.
060
061 <p>A definition of the Exponential distribution can be found at
062 <a href="http://www.cern.ch/RD11/rkb/AN16pp/node78.html#SECTION000780000000000000000"><code>http://www.cern.ch/RD11/rkb/AN16pp/node78.html#SECTION000780000000000000000</code></a>
063
064 @author David Bauer and Kostas Oikonomou (contributor: Edward A. Lee)
065 @version $Id$
066 @since Ptolemy II 4.1
067 @Pt.ProposedRating Red (cxh)
068 @Pt.AcceptedRating Red (cxh)
069 */
070public class ColtExponential extends ColtRandomSource {
071    /** Construct an actor with the given container and name.
072     *  @param container The container.
073     *  @param name The name of this actor.
074     *  @exception IllegalActionException If the actor cannot be contained
075     *   by the proposed container.
076     *  @exception NameDuplicationException If the container already has an
077     *   actor with this name.
078     */
079    public ColtExponential(CompositeEntity container, String name)
080            throws NameDuplicationException, IllegalActionException {
081        super(container, name);
082
083        output.setTypeEquals(BaseType.DOUBLE);
084
085        lambda = new PortParameter(this, "lambda", new DoubleToken(1.0));
086        lambda.setTypeEquals(BaseType.DOUBLE);
087        new SingletonParameter(lambda.getPort(), "_showName")
088                .setToken(BooleanToken.TRUE);
089
090        lambda.moveToFirst();
091    }
092
093    ///////////////////////////////////////////////////////////////////
094    ////                     ports and parameters                  ////
095
096    /** The mean value of the exponential.
097     *  This is a double with default value 1.0.
098     */
099    public PortParameter lambda;
100
101    ///////////////////////////////////////////////////////////////////
102    ////                         public methods                    ////
103
104    /** Send a random number with a Exponential distribution to the output.
105     *  This number is only changed in the prefire() method, so it will
106     *  remain constant throughout an iteration.
107     *  @exception IllegalActionException If there is no director.
108     */
109    @Override
110    public void fire() throws IllegalActionException {
111        lambda.update();
112        super.fire();
113        output.send(0, new DoubleToken(_current));
114    }
115
116    ///////////////////////////////////////////////////////////////////
117    ////                         protected methods                 ////
118
119    /** Method that is called after _randomNumberGenerator is changed.
120     */
121    @Override
122    protected void _createdNewRandomNumberGenerator() {
123        _generator = new Exponential(1.0, _randomNumberGenerator);
124    }
125
126    /** Generate a new random number.
127     *  @exception IllegalActionException If parameter values are incorrect.
128     */
129    @Override
130    protected void _generateRandomNumber() throws IllegalActionException {
131        double lambdaValue = ((DoubleToken) lambda.getToken()).doubleValue();
132        _current = _generator.nextDouble(lambdaValue);
133    }
134
135    ///////////////////////////////////////////////////////////////////
136    ////                         private variables                 ////
137
138    /** The random number for the current iteration. */
139    private double _current;
140
141    /** The random number generator. */
142    private Exponential _generator;
143}