source: src/main/java/agents/org/apache/commons/math/random/AbstractWell.java

Last change on this file was 1, checked in by Wouter Pasman, 7 years ago

Initial import : Genius 9.0.0
File size: 7.4 KB
Line 
1/*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17package agents.org.apache.commons.math.random;
18
19import java.io.Serializable;
20
21
22/** This abstract class implements the WELL class of pseudo-random number generator
23 * from François Panneton, Pierre L'Ecuyer and Makoto Matsumoto.
24
25 * <p>This generator is described in a paper by Fran&ccedil;ois Panneton,
26 * Pierre L'Ecuyer and Makoto Matsumoto <a
27 * href="http://www.iro.umontreal.ca/~lecuyer/myftp/papers/wellrng.pdf">Improved
28 * Long-Period Generators Based on Linear Recurrences Modulo 2</a> ACM
29 * Transactions on Mathematical Software, 32, 1 (2006). The errata for the paper
30 * are in <a href="http://www.iro.umontreal.ca/~lecuyer/myftp/papers/wellrng-errata.txt">wellrng-errata.txt</a>.</p>
31
32 * @see <a href="http://www.iro.umontreal.ca/~panneton/WELLRNG.html">WELL Random number generator</a>
33 * @version $Revision: 1003892 $ $Date: 2010-10-02 23:28:56 +0200 (sam. 02 oct. 2010) $
34 * @since 2.2
35
36 */
37public abstract class AbstractWell extends BitsStreamGenerator implements Serializable {
38
39 /** Serializable version identifier. */
40 private static final long serialVersionUID = -817701723016583596L;
41
42 /** Current index in the bytes pool. */
43 protected int index;
44
45 /** Bytes pool. */
46 protected final int[] v;
47
48 /** Index indirection table giving for each index its predecessor taking table size into account. */
49 protected final int[] iRm1;
50
51 /** Index indirection table giving for each index its second predecessor taking table size into account. */
52 protected final int[] iRm2;
53
54 /** Index indirection table giving for each index the value index + m1 taking table size into account. */
55 protected final int[] i1;
56
57 /** Index indirection table giving for each index the value index + m2 taking table size into account. */
58 protected final int[] i2;
59
60 /** Index indirection table giving for each index the value index + m3 taking table size into account. */
61 protected final int[] i3;
62
63 /** Creates a new random number generator.
64 * <p>The instance is initialized using the current time as the
65 * seed.</p>
66 * @param k number of bits in the pool (not necessarily a multiple of 32)
67 * @param m1 first parameter of the algorithm
68 * @param m2 second parameter of the algorithm
69 * @param m3 third parameter of the algorithm
70 */
71 protected AbstractWell(final int k, final int m1, final int m2, final int m3) {
72 this(k, m1, m2, m3, System.currentTimeMillis());
73 }
74
75 /** Creates a new random number generator using a single int seed.
76 * @param k number of bits in the pool (not necessarily a multiple of 32)
77 * @param m1 first parameter of the algorithm
78 * @param m2 second parameter of the algorithm
79 * @param m3 third parameter of the algorithm
80 * @param seed the initial seed (32 bits integer)
81 */
82 protected AbstractWell(final int k, final int m1, final int m2, final int m3, final int seed) {
83 this(k, m1, m2, m3, new int[] { seed });
84 }
85
86 /** Creates a new random number generator using an int array seed.
87 * @param k number of bits in the pool (not necessarily a multiple of 32)
88 * @param m1 first parameter of the algorithm
89 * @param m2 second parameter of the algorithm
90 * @param m3 third parameter of the algorithm
91 * @param seed the initial seed (32 bits integers array), if null
92 * the seed of the generator will be related to the current time
93 */
94 protected AbstractWell(final int k, final int m1, final int m2, final int m3, final int[] seed) {
95
96 // the bits pool contains k bits, k = r w - p where r is the number
97 // of w bits blocks, w is the block size (always 32 in the original paper)
98 // and p is the number of unused bits in the last block
99 final int w = 32;
100 final int r = (k + w - 1) / w;
101 this.v = new int[r];
102 this.index = 0;
103
104 // precompute indirection index tables. These tables are used for optimizing access
105 // they allow saving computations like "(j + r - 2) % r" with costly modulo operations
106 iRm1 = new int[r];
107 iRm2 = new int[r];
108 i1 = new int[r];
109 i2 = new int[r];
110 i3 = new int[r];
111 for (int j = 0; j < r; ++j) {
112 iRm1[j] = (j + r - 1) % r;
113 iRm2[j] = (j + r - 2) % r;
114 i1[j] = (j + m1) % r;
115 i2[j] = (j + m2) % r;
116 i3[j] = (j + m3) % r;
117 }
118
119 // initialize the pool content
120 setSeed(seed);
121
122 }
123
124 /** Creates a new random number generator using a single long seed.
125 * @param k number of bits in the pool (not necessarily a multiple of 32)
126 * @param m1 first parameter of the algorithm
127 * @param m2 second parameter of the algorithm
128 * @param m3 third parameter of the algorithm
129 * @param seed the initial seed (64 bits integer)
130 */
131 protected AbstractWell(final int k, final int m1, final int m2, final int m3, final long seed) {
132 this(k, m1, m2, m3, new int[] { (int) (seed >>> 32), (int) (seed & 0xffffffffl) });
133 }
134
135 /** Reinitialize the generator as if just built with the given int seed.
136 * <p>The state of the generator is exactly the same as a new
137 * generator built with the same seed.</p>
138 * @param seed the initial seed (32 bits integer)
139 */
140 @Override
141 public void setSeed(final int seed) {
142 setSeed(new int[] { seed });
143 }
144
145 /** Reinitialize the generator as if just built with the given int array seed.
146 * <p>The state of the generator is exactly the same as a new
147 * generator built with the same seed.</p>
148 * @param seed the initial seed (32 bits integers array), if null
149 * the seed of the generator will be related to the current time
150 */
151 @Override
152 public void setSeed(final int[] seed) {
153
154 if (seed == null) {
155 setSeed(System.currentTimeMillis());
156 return;
157 }
158
159 System.arraycopy(seed, 0, v, 0, Math.min(seed.length, v.length));
160
161 if (seed.length < v.length) {
162 for (int i = seed.length; i < v.length; ++i) {
163 final long l = v[i - seed.length];
164 v[i] = (int) ((1812433253l * (l ^ (l >> 30)) + i) & 0xffffffffL);
165 }
166 }
167
168 index = 0;
169
170 }
171
172 /** Reinitialize the generator as if just built with the given long seed.
173 * <p>The state of the generator is exactly the same as a new
174 * generator built with the same seed.</p>
175 * @param seed the initial seed (64 bits integer)
176 */
177 @Override
178 public void setSeed(final long seed) {
179 setSeed(new int[] { (int) (seed >>> 32), (int) (seed & 0xffffffffl) });
180 }
181
182 /** {@inheritDoc} */
183 @Override
184 protected abstract int next(final int bits);
185
186}
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