94 lines
2.8 KiB
Java
94 lines
2.8 KiB
Java
//******************************************************************************
|
|
//
|
|
// File: UniformPrng.java
|
|
// Package: edu.rit.numeric
|
|
// Unit: Class edu.rit.numeric.UniformPrng
|
|
//
|
|
// This Java source file is copyright (C) 2013 by Alan Kaminsky. All rights
|
|
// reserved. For further information, contact the author, Alan Kaminsky, at
|
|
// ark@cs.rit.edu.
|
|
//
|
|
// This Java source file is part of the Parallel Java 2 Library ("PJ2"). PJ2 is
|
|
// free software; you can redistribute it and/or modify it under the terms of
|
|
// the GNU General Public License as published by the Free Software Foundation;
|
|
// either version 3 of the License, or (at your option) any later version.
|
|
//
|
|
// PJ2 is distributed in the hope that it will be useful, but WITHOUT ANY
|
|
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
|
|
// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
|
|
//
|
|
// A copy of the GNU General Public License is provided in the file gpl.txt. You
|
|
// may also obtain a copy of the GNU General Public License on the World Wide
|
|
// Web at http://www.gnu.org/licenses/gpl.html.
|
|
//
|
|
//******************************************************************************
|
|
|
|
package edu.rit.numeric;
|
|
|
|
import edu.rit.util.Random;
|
|
|
|
/**
|
|
* Class UniformPrng provides a pseudorandom number generator (PRNG) that
|
|
* generates random numbers with a uniform(<I>a,b</I>) distribution. The
|
|
* probability density function is
|
|
* <BR> <I>f</I>(<I>x</I>) = 1/(<I>b</I> − <I>a</I>), <I>a</I> ≤ <I>x</I> ≤ <I>b</I>
|
|
* <BR> <I>f</I>(<I>x</I>) = 0, otherwise
|
|
* <P>
|
|
* Every call of the <TT>next()</TT> method results in one call of the
|
|
* underlying uniform PRNG's <TT>nextDouble()</TT> method.
|
|
*
|
|
* @author Alan Kaminsky
|
|
* @version 04-Aug-2011
|
|
*/
|
|
public class UniformPrng
|
|
extends DoublePrng
|
|
{
|
|
|
|
// Hidden data members.
|
|
|
|
private double a;
|
|
private double b_minus_a;
|
|
|
|
// Exported constructors.
|
|
|
|
/**
|
|
* Construct a new uniform PRNG.
|
|
*
|
|
* @param theUniformPrng The underlying uniform PRNG.
|
|
* @param a Interval lower bound.
|
|
* @param b Interval upper bound.
|
|
*
|
|
* @exception NullPointerException
|
|
* (unchecked exception) Thrown if <TT>theUniformPrng</TT> is null.
|
|
* @exception IllegalArgumentException
|
|
* (unchecked exception) Thrown if <I>a</I> ≥ <I>b</I>.
|
|
*/
|
|
public UniformPrng
|
|
(Random theUniformPrng,
|
|
double a,
|
|
double b)
|
|
{
|
|
super (theUniformPrng);
|
|
if (a >= b)
|
|
{
|
|
throw new IllegalArgumentException
|
|
("UniformPrng(): a ("+a+") >= b ("+b+") illegal");
|
|
}
|
|
this.a = a;
|
|
this.b_minus_a = b - a;
|
|
}
|
|
|
|
// Exported operations.
|
|
|
|
/**
|
|
* Returns the next random number.
|
|
*
|
|
* @return Random number.
|
|
*/
|
|
public double next()
|
|
{
|
|
return myUniformPrng.nextDouble()*b_minus_a + a;
|
|
}
|
|
|
|
}
|