/*
* This file is part of JGAP.
*
* JGAP offers a dual license model containing the LGPL as well as the MPL.
*
* For licensing information please see the file license.txt included with JGAP
* or have a look at the top of class org.jgap.Chromosome which representatively
* includes the JGAP license policy applicable for any file delivered with JGAP.
*/
package org.jgap.impl;
import java.util.*;
import java.io.*;
import org.jgap.*;
/**
* Cauchy probability density function (cumulative distribution function).
*
* @author Klaus Meffert
* @since 1.1
*/
public class CauchyRandomGenerator
implements RandomGenerator {
/** String containing the CVS revision. Read out via reflection!*/
private final static String CVS_REVISION = "$Revision: 1.15 $";
private double m_scale;
private double m_location;
private Random m_rn;
/**
* Defaults to location = 0.0 and scale = 1.0.
*
* @author Klaus Meffert
* @since 1.1
*/
public CauchyRandomGenerator() {
this(0.0d, 1.0d);
}
/**
* @param a_location cauchy parameter, 0 is standard
* @param a_scale cauchy parameter, 1 is standard
*
* @author Klaus Meffert
* @since 1.1
*/
public CauchyRandomGenerator(final double a_location, final double a_scale) {
m_location = a_location;
m_scale = a_scale;
m_rn = new Random();
}
public int nextInt() {
return Math.min(Integer.MAX_VALUE - 1,
(int) Math.round(nextCauchy() * Integer.MAX_VALUE));
}
public int nextInt(final int a_ceiling) {
return Math.min(a_ceiling - 1,
(int) Math.round(nextCauchy() * a_ceiling));
}
public long nextLong() {
return Math.min(Long.MAX_VALUE - 1,
Math.round(nextCauchy() * Long.MAX_VALUE));
}
public double nextDouble() {
return nextCauchy();
}
public float nextFloat() {
return Math.min(Float.MAX_VALUE - 1,
(float) (nextCauchy() * Float.MAX_VALUE));
}
public boolean nextBoolean() {
return nextCauchy() >= 0.5d;
}
/**
* Calculate Cumulative Cauchy distribution function.
*
* @return the probability that a stochastic variable x is less than X
*
* @author Klaus Meffert
* @since 1.1
*/
public double nextCauchy() {
return 0.5
+ Math.atan( (m_rn.nextDouble() - m_location) / m_scale) / Math.PI;
}
/**
* @return the cauchy standard deviation
*
* @author Klaus Meffert
* @since 1.1
*/
public double getCauchyStandardDeviation() {
return m_scale;
}
/**
* When deserializing, initialize the seed because otherwise we could get
* duplicate evolution results when doing distributed computing!
*
* @param a_inputStream the ObjectInputStream provided for deserialzation
*
* @throws IOException
* @throws ClassNotFoundException
*
* @author Klaus Meffert
* @since 3.01
*/
private void readObject(ObjectInputStream a_inputStream)
throws IOException, ClassNotFoundException {
//always perform the default de-serialization first
a_inputStream.defaultReadObject();
m_rn.setSeed(System.currentTimeMillis());
}
}