package org.spaceroots.mantissa.random;
import java.util.Random;
/** This class implements a powerful pseudo-random number generator
* developed by Makoto Matsumoto and Takuji Nishimura during
* 1996-1997.
* This generator features an extremely long period
* (219937-1) and 623-dimensional equidistribution up to 32
* bits accuracy. The home page for this generator is located at
* http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html.
* This generator is described in a paper by Makoto Matsumoto and
* Takuji Nishimura in 1998: Mersenne
* Twister: A 623-Dimensionally Equidistributed Uniform Pseudo-Random
* Number Generator, ACM Transactions on Modeling and Computer
* Simulation, Vol. 8, No. 1, January 1998, pp 3--30
* The class is implemented as a specialization of the standard
* java.util.Random class. This allows to use it in
* algorithms expecting a standard random generator, and hence benefit
* from a better generator without code change.
* This class is mainly a Java port of the 2002-01-26 version of
* the generator written in C by Makoto Matsumoto and Takuji
* Nishimura. Here is their original copyright:
*
* Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
* All rights reserved. Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* - The names of its contributors may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
* OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
* USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
* @author Makoto Matsumoto and Takuji Nishimura (C version), Luc Maisonobe (Java port)
* @version $Id: MersenneTwister.java 1666 2005-12-15 16:37:55Z luc $
*/
public class MersenneTwister
extends Random {
/** Creates a new random number generator.
* The instance is initialized using the current time as the
* seed.
*/
public MersenneTwister() {
mt = new int[N];
setSeed(System.currentTimeMillis());
}
/** Creates a new random number generator using a single int seed.
* @param seed the initial seed (32 bits integer)
*/
public MersenneTwister(int seed) {
mt = new int[N];
setSeed(seed);
}
/** Creates a new random number generator using an int array seed.
* @param seed the initial seed (32 bits integers array), if null
* the seed of the generator will be related to the current time
*/
public MersenneTwister(int[] seed) {
mt = new int[N];
setSeed(seed);
}
/** Creates a new random number generator using a single long seed.
* @param seed the initial seed (64 bits integer)
*/
public MersenneTwister(long seed) {
mt = new int[N];
setSeed(seed);
}
/** Reinitialize the generator as if just built with the given int seed.
* The state of the generator is exactly the same as a new
* generator built with the same seed.
* @param seed the initial seed (32 bits integer)
*/
public void setSeed(int seed) {
// we use a long masked by 0xffffffffL as a poor man unsigned int
long longMT = seed;
mt[0]= (int) longMT;
for (mti = 1; mti < N; ++mti) {
// See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier.
// initializer from the 2002-01-09 C version by Makoto Matsumoto
longMT = (1812433253l * (longMT ^ (longMT >> 30)) + mti) & 0xffffffffL;
mt[mti]= (int) longMT;
}
}
/** Reinitialize the generator as if just built with the given int array seed.
* The state of the generator is exactly the same as a new
* generator built with the same seed.
* @param seed the initial seed (32 bits integers array), if null
* the seed of the generator will be related to the current time
*/
public void setSeed(int[] seed) {
if (seed == null) {
setSeed(System.currentTimeMillis());
return;
}
setSeed(19650218);
int i = 1;
int j = 0;
for (int k = Math.max(N, seed.length); k != 0; k--) {
long l0 = (mt[i] & 0x7fffffffl) | ((mt[i] < 0) ? 0x80000000l : 0x0l);
long l1 = (mt[i-1] & 0x7fffffffl) | ((mt[i-1] < 0) ? 0x80000000l : 0x0l);
long l = (l0 ^ ((l1 ^ (l1 >> 30)) * 1664525l)) + seed[j] + j; // non linear
mt[i] = (int) (l & 0xffffffffl);
i++; j++;
if (i >= N) {
mt[0] = mt[N - 1];
i = 1;
}
if (j >= seed.length) {
j = 0;
}
}
for (int k = N - 1; k != 0; k--) {
long l0 = (mt[i] & 0x7fffffffl) | ((mt[i] < 0) ? 0x80000000l : 0x0l);
long l1 = (mt[i-1] & 0x7fffffffl) | ((mt[i-1] < 0) ? 0x80000000l : 0x0l);
long l = (l0 ^ ((l1 ^ (l1 >> 30)) * 1566083941l)) - i; // non linear
mt[i] = (int) (l & 0xffffffffL);
i++;
if (i >= N) {
mt[0] = mt[N - 1];
i = 1;
}
}
mt[0] = 0x80000000; // MSB is 1; assuring non-zero initial array
}
/** Reinitialize the generator as if just built with the given long seed.
* The state of the generator is exactly the same as a new
* generator built with the same seed.
* @param seed the initial seed (64 bits integer)
*/
public void setSeed(long seed) {
if (mt == null) {
// this is probably a spurious call from base class constructor,
// we do nothing and wait for the setSeed in our own
// constructors after array allocation
return;
}
setSeed(new int[] { (int) (seed >>> 32), (int) (seed & 0xffffffffl) });
}
/** Generate next pseudorandom number.
* This method is the core generation algorithm. As per
* {@link java.util.Random Random } contract, it is used by all the
* public generation methods for the various primitive types {@link
* java.util.Random#nextBoolean nextBoolean}, {@link java.util.Random#nextBytes
* nextBytes}, {@link java.util.Random#nextDouble nextDouble}, {@link
* java.util.Random#nextFloat nextFloat}, {@link java.util.Random#nextGaussian
* nextGaussian}, {@link java.util.Random#nextInt() nextInt} and {@link
* java.util.Random#nextLong nextLong}.
* @param bits number of random bits to produce
*/
protected int next(int bits) {
int y;
if (mti >= N) { // generate N words at one time
int mtNext = mt[0];
for (int k = 0; k < N - M; ++k) {
int mtCurr = mtNext;
mtNext = mt[k + 1];
y = (mtCurr & 0x80000000) | (mtNext & 0x7fffffff);
mt[k] = mt[k + M] ^ (y >>> 1) ^ MAG01[y & 0x1];
}
for (int k = N - M; k < N - 1; ++k) {
int mtCurr = mtNext;
mtNext = mt[k + 1];
y = (mtCurr & 0x80000000) | (mtNext & 0x7fffffff);
mt[k] = mt[k + (M - N)] ^ (y >>> 1) ^ MAG01[y & 0x1];
}
y = (mtNext & 0x80000000) | (mt[0] & 0x7fffffff);
mt[N - 1] = mt[M - 1] ^ (y >>> 1) ^ MAG01[y & 0x1];
mti = 0;
}
y = mt[mti++];
// tempering
y ^= (y >>> 11);
y ^= (y << 7) & 0x9d2c5680;
y ^= (y << 15) & 0xefc60000;
y ^= (y >>> 18);
return y >>> (32 - bits);
}
private static final int N = 624;
private static final int M = 397;
private static final int[] MAG01 = { 0x0, 0x9908b0df };
private int[] mt;
private int mti;
private static final long serialVersionUID = 7666069655872848609L;
}
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