| /* |
| * 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; |
| |
| |
| /** This class implements the WELL44497b pseudo-random number generator |
| * from François Panneton, Pierre L'Ecuyer and Makoto Matsumoto. |
| |
| * <p>This generator is described in a paper by François Panneton, |
| * Pierre L'Ecuyer and Makoto Matsumoto <a |
| * href="http://www.iro.umontreal.ca/~lecuyer/myftp/papers/wellrng.pdf">Improved |
| * Long-Period Generators Based on Linear Recurrences Modulo 2</a> ACM |
| * Transactions on Mathematical Software, 32, 1 (2006). The errata for the paper |
| * are in <a href="http://www.iro.umontreal.ca/~lecuyer/myftp/papers/wellrng-errata.txt">wellrng-errata.txt</a>.</p> |
| |
| * @see <a href="http://www.iro.umontreal.ca/~panneton/WELLRNG.html">WELL Random number generator</a> |
| * @version $Revision: 1003892 $ $Date: 2010-10-02 23:28:56 +0200 (sam. 02 oct. 2010) $ |
| * @since 2.2 |
| |
| */ |
| public class Well44497b extends AbstractWell { |
| |
| /** Serializable version identifier. */ |
| private static final long serialVersionUID = 4032007538246675492L; |
| |
| /** Number of bits in the pool. */ |
| private static final int K = 44497; |
| |
| /** First parameter of the algorithm. */ |
| private static final int M1 = 23; |
| |
| /** Second parameter of the algorithm. */ |
| private static final int M2 = 481; |
| |
| /** Third parameter of the algorithm. */ |
| private static final int M3 = 229; |
| |
| /** Creates a new random number generator. |
| * <p>The instance is initialized using the current time as the |
| * seed.</p> |
| */ |
| public Well44497b() { |
| super(K, M1, M2, M3); |
| } |
| |
| /** Creates a new random number generator using a single int seed. |
| * @param seed the initial seed (32 bits integer) |
| */ |
| public Well44497b(int seed) { |
| super(K, M1, M2, M3, 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 Well44497b(int[] seed) { |
| super(K, M1, M2, M3, seed); |
| } |
| |
| /** Creates a new random number generator using a single long seed. |
| * @param seed the initial seed (64 bits integer) |
| */ |
| public Well44497b(long seed) { |
| super(K, M1, M2, M3, seed); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| protected int next(final int bits) { |
| |
| // compute raw value given by WELL44497a generator |
| // which is NOT maximally-equidistributed |
| final int indexRm1 = iRm1[index]; |
| final int indexRm2 = iRm2[index]; |
| |
| final int v0 = v[index]; |
| final int vM1 = v[i1[index]]; |
| final int vM2 = v[i2[index]]; |
| final int vM3 = v[i3[index]]; |
| |
| // the values below include the errata of the original article |
| final int z0 = (0xFFFF8000 & v[indexRm1]) ^ (0x00007FFF & v[indexRm2]); |
| final int z1 = (v0 ^ (v0 << 24)) ^ (vM1 ^ (vM1 >>> 30)); |
| final int z2 = (vM2 ^ (vM2 << 10)) ^ (vM3 << 26); |
| final int z3 = z1 ^ z2; |
| final int z2Prime = ((z2 << 9) ^ (z2 >>> 23)) & 0xfbffffff; |
| final int z2Second = ((z2 & 0x00020000) != 0) ? (z2Prime ^ 0xb729fcec) : z2Prime; |
| int z4 = z0 ^ (z1 ^ (z1 >>> 20)) ^ z2Second ^ z3; |
| |
| v[index] = z3; |
| v[indexRm1] = z4; |
| v[indexRm2] &= 0xFFFF8000; |
| index = indexRm1; |
| |
| // add Matsumoto-Kurita tempering |
| // to get a maximally-equidistributed generator |
| z4 = z4 ^ ((z4 << 7) & 0x93dd1400); |
| z4 = z4 ^ ((z4 << 15) & 0xfa118000); |
| |
| return z4 >>> (32 - bits); |
| |
| } |
| |
| } |