107 lines
3.2 KiB
Java
107 lines
3.2 KiB
Java
//******************************************************************************
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//
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// File: BernoulliPrng.java
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// Package: edu.rit.numeric
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// Unit: Class edu.rit.numeric.BernoulliPrng
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//
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// This Java source file is copyright (C) 2013 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.numeric;
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import edu.rit.util.Random;
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/**
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* Class BernoulliPrng provides a pseudorandom number generator (PRNG) that
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* generates random values of type <TT>boolean</TT>. The probability of the
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* value true (heads) is <I>p</I>, specified to the constructor. The probability
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* of the value false (tails) is <I>q</I> = 1 − <I>p</I>.
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*
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* @author Alan Kaminsky
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* @version 07-Jun-2011
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*/
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public class BernoulliPrng
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{
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// Hidden data members.
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private final Random myUniformPrng;
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private final double myP;
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// Exported constructors.
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/**
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* Construct a new Bernoulli PRNG with heads probability = 0.5.
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*
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* @param theUniformPrng The underlying uniform PRNG.
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*
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* @exception NullPointerException
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* (unchecked exception) Thrown if <TT>theUniformPrng</TT> is null.
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*/
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public BernoulliPrng
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(Random theUniformPrng)
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{
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this (theUniformPrng, 0.5);
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}
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/**
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* Construct a new Bernoulli PRNG with the given heads probability.
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*
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* @param theUniformPrng The underlying uniform PRNG.
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* @param p Heads probability, 0 ≤ <I>p</I> ≤ 1.
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*
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* @exception NullPointerException
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* (unchecked exception) Thrown if <TT>theUniformPrng</TT> is null.
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* @exception IllegalArgumentException
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* (unchecked exception) Thrown if <I>p</I> < 0 or <I>p</I> > 1.
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*/
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public BernoulliPrng
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(Random theUniformPrng,
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double p)
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{
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if (theUniformPrng == null)
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{
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throw new NullPointerException
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("BernoulliPrng(): theUniformPrng is null");
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}
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if (0.0 > p || p > 1.0)
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{
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throw new IllegalArgumentException
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("BernoulliPrng(): p = "+p+" illegal");
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}
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myUniformPrng = theUniformPrng;
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myP = p;
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}
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// Exported operations.
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/**
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* Returns the next random value. True (heads) is returned with probability
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* <I>p</I>, false (tails) is returned with probability
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* 1 − <I>p</I>.
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*
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* @return Random value.
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*/
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public boolean next()
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{
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return myUniformPrng.nextDouble() < myP;
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}
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}
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