/* An actor that outputs a random sequence with a Binomial 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
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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
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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.IntToken;
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.Binomial;
//////////////////////////////////////////////////////////////////////////
//// Binomial
/**
Produce a random sequence with a Binomial 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 mean 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/Binomial.html">cern.jet.random.Binomial</a> object with
n, the number of trials (also known as the sample size) set to 1
and p, the probability of success, set to 0.5.
A definition of Binomial by Wolfgang Hoschek can be found at
<a href="http://hoschek.home.cern.ch/hoschek/colt/V1.0.3/doc/cern/jet/stat/Probability.html#binomial(int,%20int,%20double)"><code>http://hoschek.home.cern.ch/hoschek/colt/V1.0.3/doc/cern/jet/stat/Probability.html#binomial(int,%20int,%20double)</code></a>:
<blockquote>
<h3>
binomial</h3>
<pre>public static double <b>binomial</b>(int k,
int n,
double p)</pre>
<p>Returns the sum of the terms <tt>0</tt> through <tt>k</tt> of the Binomial
probability density.
<pre> k
-- ( n ) j n-j
> ( ) p (1-p)
-- ( j )
j=0
</pre>
The terms are not summed directly; instead the incomplete
beta integral is employed, according to the formula
<p>
<tt>y = binomial( k, n, p ) = Gamma.incompleteBeta( n-k, k+1, 1-p )</tt>.
</p><p>
All arguments must be positive,</p>
<p><b>Parameters:</b>
<br><code>k</code> - end term.
<br><code>n</code> - the number of trials.
<br><code>p</code> - the probability of success (must be in <tt>(0.0,1.0)</tt>).
</blockquote>
The above description of binomial() is
<a href="doc-files/colt-copyright.htm">copyrighted</a>.
@author David Bauer and Kostas Oikonomou
@version $Id$
@since Ptolemy II 4.1
@Pt.ProposedRating Red (cxh)
@Pt.AcceptedRating Red (cxh)
*/
public class ColtBinomial 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 ColtBinomial(CompositeEntity container, String name)
throws NameDuplicationException, IllegalActionException {
super(container, name);
output.setTypeEquals(BaseType.INT);
n = new PortParameter(this, "n", new IntToken(1));
n.setTypeEquals(BaseType.INT);
new SingletonParameter(n.getPort(), "_showName")
.setToken(BooleanToken.TRUE);
p = new PortParameter(this, "p", new DoubleToken(0.5));
p.setTypeEquals(BaseType.DOUBLE);
new SingletonParameter(p.getPort(), "_showName")
.setToken(BooleanToken.TRUE);
p.moveToFirst();
n.moveToFirst();
}
///////////////////////////////////////////////////////////////////
//// ports and parameters ////
/** n.
* This has type int with default 1.
*/
public PortParameter n;
/** p.
* This has type double with default 0.5.
*/
public PortParameter p;
///////////////////////////////////////////////////////////////////
//// public methods ////
/** Send a random number with a Binomial 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 {
n.update();
p.update();
super.fire();
output.send(0, new IntToken(_current));
}
///////////////////////////////////////////////////////////////////
//// protected methods ////
/** Method that is called after _randomNumberGenerator is changed.
*/
protected void _createdNewRandomNumberGenerator() {
_generator = new Binomial(1, 0.5, _randomNumberGenerator);
}
/** Generate a new random number.
* @exception IllegalActionException If parameter values are incorrect.
*/
protected void _generateRandomNumber() throws IllegalActionException {
// The following logic protects the binomial generation call
// because the Colt library will throw an exception (even
// though they are valid limit cases). The limits can occur
// during the course of a simulation, and this actor should
// produce valid results if they do occur.
int nValue = ((IntToken) n.getToken()).intValue();
if (nValue == 0) {
_current = 0;
} else {
double pValue = ((DoubleToken) p.getToken()).doubleValue();
if (pValue == 0.0) {
_current = 0;
} else if (pValue == 1.0) {
_current = nValue;
} else {
_current = _generator.nextInt(nValue, pValue);
}
}
}
///////////////////////////////////////////////////////////////////
//// private variables ////
/** The random number for the current iteration. */
private int _current;
/** The random number generator. */
private Binomial _generator;
}