| /* |
| * 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; |
| |
| |
| /** This abstract class implements the WELL class of 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 abstract class AbstractWell extends BitsStreamGenerator implements Serializable { |
| |
| /** Serializable version identifier. */ |
| private static final long serialVersionUID = -817701723016583596L; |
| |
| /** Current index in the bytes pool. */ |
| protected int index; |
| |
| /** Bytes pool. */ |
| protected final int[] v; |
| |
| /** Index indirection table giving for each index its predecessor taking table size into account. */ |
| protected final int[] iRm1; |
| |
| /** Index indirection table giving for each index its second predecessor taking table size into account. */ |
| protected final int[] iRm2; |
| |
| /** Index indirection table giving for each index the value index + m1 taking table size into account. */ |
| protected final int[] i1; |
| |
| /** Index indirection table giving for each index the value index + m2 taking table size into account. */ |
| protected final int[] i2; |
| |
| /** Index indirection table giving for each index the value index + m3 taking table size into account. */ |
| protected final int[] i3; |
| |
| /** Creates a new random number generator. |
| * <p>The instance is initialized using the current time as the |
| * seed.</p> |
| * @param k number of bits in the pool (not necessarily a multiple of 32) |
| * @param m1 first parameter of the algorithm |
| * @param m2 second parameter of the algorithm |
| * @param m3 third parameter of the algorithm |
| */ |
| protected AbstractWell(final int k, final int m1, final int m2, final int m3) { |
| this(k, m1, m2, m3, System.currentTimeMillis()); |
| } |
| |
| /** Creates a new random number generator using a single int seed. |
| * @param k number of bits in the pool (not necessarily a multiple of 32) |
| * @param m1 first parameter of the algorithm |
| * @param m2 second parameter of the algorithm |
| * @param m3 third parameter of the algorithm |
| * @param seed the initial seed (32 bits integer) |
| */ |
| protected AbstractWell(final int k, final int m1, final int m2, final int m3, final int seed) { |
| this(k, m1, m2, m3, new int[] { seed }); |
| } |
| |
| /** Creates a new random number generator using an int array seed. |
| * @param k number of bits in the pool (not necessarily a multiple of 32) |
| * @param m1 first parameter of the algorithm |
| * @param m2 second parameter of the algorithm |
| * @param m3 third parameter of the algorithm |
| * @param seed the initial seed (32 bits integers array), if null |
| * the seed of the generator will be related to the current time |
| */ |
| protected AbstractWell(final int k, final int m1, final int m2, final int m3, final int[] seed) { |
| |
| // the bits pool contains k bits, k = r w - p where r is the number |
| // of w bits blocks, w is the block size (always 32 in the original paper) |
| // and p is the number of unused bits in the last block |
| final int w = 32; |
| final int r = (k + w - 1) / w; |
| this.v = new int[r]; |
| this.index = 0; |
| |
| // precompute indirection index tables. These tables are used for optimizing access |
| // they allow saving computations like "(j + r - 2) % r" with costly modulo operations |
| iRm1 = new int[r]; |
| iRm2 = new int[r]; |
| i1 = new int[r]; |
| i2 = new int[r]; |
| i3 = new int[r]; |
| for (int j = 0; j < r; ++j) { |
| iRm1[j] = (j + r - 1) % r; |
| iRm2[j] = (j + r - 2) % r; |
| i1[j] = (j + m1) % r; |
| i2[j] = (j + m2) % r; |
| i3[j] = (j + m3) % r; |
| } |
| |
| // initialize the pool content |
| setSeed(seed); |
| |
| } |
| |
| /** Creates a new random number generator using a single long seed. |
| * @param k number of bits in the pool (not necessarily a multiple of 32) |
| * @param m1 first parameter of the algorithm |
| * @param m2 second parameter of the algorithm |
| * @param m3 third parameter of the algorithm |
| * @param seed the initial seed (64 bits integer) |
| */ |
| protected AbstractWell(final int k, final int m1, final int m2, final int m3, final long seed) { |
| this(k, m1, m2, m3, new int[] { (int) (seed >>> 32), (int) (seed & 0xffffffffl) }); |
| } |
| |
| /** 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(final int seed) { |
| setSeed(new int[] { seed }); |
| } |
| |
| /** 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(final int[] seed) { |
| |
| if (seed == null) { |
| setSeed(System.currentTimeMillis()); |
| return; |
| } |
| |
| System.arraycopy(seed, 0, v, 0, Math.min(seed.length, v.length)); |
| |
| if (seed.length < v.length) { |
| for (int i = seed.length; i < v.length; ++i) { |
| final long l = v[i - seed.length]; |
| v[i] = (int) ((1812433253l * (l ^ (l >> 30)) + i) & 0xffffffffL); |
| } |
| } |
| |
| index = 0; |
| |
| } |
| |
| /** 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(final long seed) { |
| setSeed(new int[] { (int) (seed >>> 32), (int) (seed & 0xffffffffl) }); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| protected abstract int next(final int bits); |
| |
| } |