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java.lang.Object org.alicebot.server.core.util.MersenneTwisterFast
public class MersenneTwisterFast
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  

MersenneTwisterFast()
Constructor using the default seed. 

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

static void 
main(java.lang.String[] args)
Tests the code. 
boolean 
nextBoolean()

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()

void 
nextBytes(byte[] bytes)

char 
nextChar()

double 
nextDouble()

float 
nextFloat()

double 
nextGaussian()

int 
nextInt()

int 
nextInt(int n)
Returns an integer drawn uniformly from 0 to n1. 
long 
nextLong()

short 
nextShort()

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.lang.Object 

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

public MersenneTwisterFast()
public MersenneTwisterFast(long seed)
Method Detail 

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


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