| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.commons.math.random; |
| |
| import java.io.Serializable; |
| |
| import org.apache.commons.math.util.FastMath; |
| |
| |
| /** This class implements a powerful pseudo-random number generator |
| * developed by Makoto Matsumoto and Takuji Nishimura during |
| * 1996-1997. |
| |
| * <p>This generator features an extremely long period |
| * (2<sup>19937</sup>-1) and 623-dimensional equidistribution up to 32 |
| * bits accuracy. The home page for this generator is located at <a |
| * href="http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html"> |
| * http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html</a>.</p> |
| |
| * <p>This generator is described in a paper by Makoto Matsumoto and |
| * Takuji Nishimura in 1998: <a |
| * href="http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/ARTICLES/mt.pdf">Mersenne |
| * Twister: A 623-Dimensionally Equidistributed Uniform Pseudo-Random |
| * Number Generator</a>, ACM Transactions on Modeling and Computer |
| * Simulation, Vol. 8, No. 1, January 1998, pp 3--30</p> |
| |
| * <p>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:</p> |
| |
| * <table border="0" width="80%" cellpadding="10" align="center" bgcolor="#E0E0E0"> |
| * <tr><td>Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura, |
| * All rights reserved.</td></tr> |
| |
| * <tr><td>Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * <ol> |
| * <li>Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer.</li> |
| * <li>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.</li> |
| * <li>The names of its contributors may not be used to endorse or promote |
| * products derived from this software without specific prior written |
| * permission.</li> |
| * </ol></td></tr> |
| |
| * <tr><td><strong>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.</strong></td></tr> |
| * </table> |
| |
| * @version $Revision: 990655 $ $Date: 2010-08-29 23:49:40 +0200 (dim. 29 août 2010) $ |
| * @since 2.0 |
| |
| */ |
| public class MersenneTwister extends BitsStreamGenerator implements Serializable { |
| |
| /** Serializable version identifier. */ |
| private static final long serialVersionUID = 8661194735290153518L; |
| |
| /** Size of the bytes pool. */ |
| private static final int N = 624; |
| |
| /** Period second parameter. */ |
| private static final int M = 397; |
| |
| /** X * MATRIX_A for X = {0, 1}. */ |
| private static final int[] MAG01 = { 0x0, 0x9908b0df }; |
| |
| /** Bytes pool. */ |
| private int[] mt; |
| |
| /** Current index in the bytes pool. */ |
| private int mti; |
| |
| /** Creates a new random number generator. |
| * <p>The instance is initialized using the current time as the |
| * seed.</p> |
| */ |
| 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. |
| * <p>The state of the generator is exactly the same as a new |
| * generator built with the same seed.</p> |
| * @param seed the initial seed (32 bits integer) |
| */ |
| @Override |
| 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. |
| * <p>The state of the generator is exactly the same as a new |
| * generator built with the same seed.</p> |
| * @param seed the initial seed (32 bits integers array), if null |
| * the seed of the generator will be related to the current time |
| */ |
| @Override |
| public void setSeed(int[] seed) { |
| |
| if (seed == null) { |
| setSeed(System.currentTimeMillis()); |
| return; |
| } |
| |
| setSeed(19650218); |
| int i = 1; |
| int j = 0; |
| |
| for (int k = FastMath.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. |
| * <p>The state of the generator is exactly the same as a new |
| * generator built with the same seed.</p> |
| * @param seed the initial seed (64 bits integer) |
| */ |
| @Override |
| public void setSeed(long seed) { |
| setSeed(new int[] { (int) (seed >>> 32), (int) (seed & 0xffffffffl) }); |
| } |
| |
| /** Generate next pseudorandom number. |
| * <p>This method is the core generation algorithm. It is used by all the |
| * public generation methods for the various primitive types {@link |
| * #nextBoolean()}, {@link #nextBytes(byte[])}, {@link #nextDouble()}, |
| * {@link #nextFloat()}, {@link #nextGaussian()}, {@link #nextInt()}, |
| * {@link #next(int)} and {@link #nextLong()}.</p> |
| * @param bits number of random bits to produce |
| * @return random bits generated |
| */ |
| @Override |
| 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); |
| |
| } |
| |
| } |
