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java.lang.Object java.util.Random org.alicebot.server.core.util.MersenneTwister
public class MersenneTwister
Version 3, based on version MT199937(99/10/29) of the Mersenne Twister algorithm found at The Mersenne Twister Home Page. By Sean Luke, June 2000.
MersenneTwister is a dropin subclass replacement for java.util.Random. It is properly synchronized and can be used in a multithreaded environment.
MersenneTwisterFast is not a subclass of java.util.Random. It has the same public methods as Random does, however, and it is algorithmically identical to MersenneTwister. MersenneTwisterFast has hardcode inlined all of its methods directly, and made all of them final (well, the ones of consequence anyway). Further, these methods are not synchronized, so the same MersenneTwisterFast instance cannot be shared by multiple threads. But all this helps MersenneTwisterFast achieve over twice the speed of MersenneTwister.
This is a Java version of the Cprogram for MT19937: Integer version. The MT19937 algorithm was created by Makoto Matsumoto and Takuji Nishimura, who ask: "When you use this, send an email to: matumoto@math.keio.ac.jp with an appropriate reference to your work". Indicate that this is a translation of their algorithm into Java.
Reference. Makato Matsumoto and Takuji Nishimura, "Mersenne Twister: A 623Dimensionally Equidistributed Uniform PseudoRandom Number Generator", ACM Transactions on Modeling and Computer Simulation, Vol. 8, No. 1, January 1998, pp 330.
This code is based on standard MT19937 C/C++ code by Takuji Nishimura, with suggestions from Topher Cooper and Marc Rieffel, July 1997. The code was originally translated into Java by Michael Lecuyer, January 1999, and is Copyright (c) 1999 by Michael Lecuyer. The included license is as follows:
The basic algorithmic work of this library (appearing in nextInt() and setSeed()) is free software; you can redistribute it and or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.This library 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 Library General Public License for more details. You should have received a copy of the GNU Library General Public License along with this library; if not, write to the Free Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 021111307 USA
This implementation implements the bug fixes made in Java 1.2's version of Random, which means it can be used with earlier versions of Java. See the JDK 1.2 java.util.Random documentation for further documentation on the randomnumber generation contracts made. Additionally, there's an undocumented bug in the JDK java.util.Random.nextBytes() method, which this code fixes.
Just like java.util.Random, this generator accepts a long seed but doesn't use all of it. java.util.Random uses 48 bits. The Mersenne Twister instead uses 32 bits (int size). So it's best if your seed does not exceed the int range.
MersenneTwister can be used reliably on JDK version 1.1.5 or above. Earlier Java versions have serious bugs in java.util.Random; only MersenneTwisterFast (and not MersenneTwister nor java.util.Random) should be used with them. And why would you use 'em anyway? They're very slow, as you'll see. Here are some timings in milliseconds on a Sun Creator3D/Ultra 60 running SunOS 5.6.
Constructor Summary  

MersenneTwister()
Constructor using the default seed. 

MersenneTwister(long seed)
Constructor using a given seed. 
Method Summary  

static void 
main(java.lang.String[] args)
Tests the code. 
protected int 
next(int bits)
Returns an integer with bits bits filled with a random number. 
boolean 
nextBoolean()
This method is missing from jdk 1.0.x and below. 
boolean 
nextBoolean(double probability)
This generates a coin flip with a probability probability of returning true, else returning false. 
boolean 
nextBoolean(float probability)
This generates a coin flip with a probability probability of returning true, else returning false. 
byte 
nextByte()
For completeness' sake, though it's not in java.util.Random. 
void 
nextBytes(byte[] bytes)
A bug fix for all versions of the JDK. 
char 
nextChar()
For completeness' sake, though it's not in java.util.Random. 
double 
nextDouble()
A bug fix for versions of JDK 1.1 and below. 
float 
nextFloat()
A bug fix for versions of JDK 1.1 and below. 
double 
nextGaussian()
A bug fix for all JDK code including 1.2. 
int 
nextInt(int n)
This method is missing from JDK 1.1 and below. 
short 
nextShort()
For completeness' sake, though it's not in java.util.Random. 
void 
setSeed(int[] array)
An alternative, more complete, method of seeding the pseudo random number generator. 
void 
setSeed(long seed)
Initalize the pseudo random number generator. 
void 
setSeedOld(long seed)
Initalize the pseudo random number generator. 
Methods inherited from class java.util.Random 

nextInt, nextLong 
Methods inherited from class java.lang.Object 

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait 
Constructor Detail 

public MersenneTwister()
public MersenneTwister(long seed)
Method Detail 

public void setSeedOld(long seed)
public void setSeed(int[] array)
public void setSeed(long seed)
setSeed
in class java.util.Random
protected int next(int bits)
next
in class java.util.Random
public boolean nextBoolean()
nextBoolean
in class java.util.Random
public boolean nextBoolean(float probability)
public boolean nextBoolean(double probability)
public int nextInt(int n)
nextInt
in class java.util.Random
public double nextDouble()
nextDouble
in class java.util.Random
public float nextFloat()
nextFloat
in class java.util.Random
public void nextBytes(byte[] bytes)
nextBytes
in class java.util.Random
public char nextChar()
public short nextShort()
public byte nextByte()
public double nextGaussian()
nextGaussian
in class java.util.Random
public static void main(java.lang.String[] args)


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