/* An actor that outputs a random sequence with a Exponential distribution.
Copyright (c) 2004-2006 The Regents of the University of California.
All rights reserved.
Permission is hereby granted, without written agreement and without
license or royalty fees, to use, copy, modify, and distribute this
software and its documentation for any purpose, provided that the above
copyright notice and the following two paragraphs appear in all copies
of this software.
IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
CALIFORNIA HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
ENHANCEMENTS, OR MODIFICATIONS.
PT_COPYRIGHT_VERSION_2
COPYRIGHTENDKEY
*/
package ptolemy.actor.lib.colt;
import ptolemy.actor.parameters.PortParameter;
import ptolemy.data.BooleanToken;
import ptolemy.data.DoubleToken;
import ptolemy.data.expr.SingletonParameter;
import ptolemy.data.type.BaseType;
import ptolemy.kernel.CompositeEntity;
import ptolemy.kernel.util.IllegalActionException;
import ptolemy.kernel.util.NameDuplicationException;
import cern.jet.random.Exponential;
//////////////////////////////////////////////////////////////////////////
//// Exponential
/**
Produce a random sequence with a Exponential distribution. On each
iteration, a new random number is produced. The output port is of
type DoubleToken. The values that are generated are independent
and identically distributed with the lambda and the standard
deviation given by parameters. In addition, the seed can be
specified as a parameter to control the sequence that is generated.
<p> This actor instantiates a
<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
lambda set to 1.0. The distribution is defined as
<pre>
p(x) = lambda*exp(-x*lambda) for x >= 0, lambda > 0
</pre>
The above description of Exponential is
<a href="doc-files/colt-copyright.htm">copyrighted</a>.
<p>A definition of the Exponential distribution can be found at
<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>
@author David Bauer and Kostas Oikonomou (contributor: Edward A. Lee)
@version $Id: ColtExponential.java,v 1.27 2006/08/20 19:55:32 cxh Exp $
@since Ptolemy II 4.1
@Pt.ProposedRating Red (cxh)
@Pt.AcceptedRating Red (cxh)
*/
public class ColtExponential extends ColtRandomSource {
/** Construct an actor with the given container and name.
* @param container The container.
* @param name The name of this actor.
* @exception IllegalActionException If the actor cannot be contained
* by the proposed container.
* @exception NameDuplicationException If the container already has an
* actor with this name.
*/
public ColtExponential(CompositeEntity container, String name)
throws NameDuplicationException, IllegalActionException {
super(container, name);
output.setTypeEquals(BaseType.DOUBLE);
lambda = new PortParameter(this, "lambda", new DoubleToken(1.0));
lambda.setTypeEquals(BaseType.DOUBLE);
new SingletonParameter(lambda.getPort(), "_showName")
.setToken(BooleanToken.TRUE);
lambda.moveToFirst();
}
///////////////////////////////////////////////////////////////////
//// ports and parameters ////
/** The mean value of the exponential.
* This is a double with default value 1.0.
*/
public PortParameter lambda;
///////////////////////////////////////////////////////////////////
//// public methods ////
/** Send a random number with a Exponential distribution to the output.
* This number is only changed in the prefire() method, so it will
* remain constant throughout an iteration.
* @exception IllegalActionException If there is no director.
*/
public void fire() throws IllegalActionException {
lambda.update();
super.fire();
output.send(0, new DoubleToken(_current));
}
///////////////////////////////////////////////////////////////////
//// protected methods ////
/** Method that is called after _randomNumberGenerator is changed.
*/
protected void _createdNewRandomNumberGenerator() {
_generator = new Exponential(1.0, _randomNumberGenerator);
}
/** Generate a new random number.
* @exception IllegalActionException If parameter values are incorrect.
*/
protected void _generateRandomNumber() throws IllegalActionException {
double lambdaValue = ((DoubleToken) lambda.getToken()).doubleValue();
_current = _generator.nextDouble(lambdaValue);
}
///////////////////////////////////////////////////////////////////
//// private variables ////
/** The random number for the current iteration. */
private double _current;
/** The random number generator. */
private Exponential _generator;
}