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Diffstat (limited to 'src/main/java/org/apache/commons/math3/random/Well1024a.java')
| -rw-r--r-- | src/main/java/org/apache/commons/math3/random/Well1024a.java | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math3/random/Well1024a.java b/src/main/java/org/apache/commons/math3/random/Well1024a.java new file mode 100644 index 0000000..72c7f16 --- /dev/null +++ b/src/main/java/org/apache/commons/math3/random/Well1024a.java @@ -0,0 +1,110 @@ +/* + * 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.math3.random; + +/** + * This class implements the WELL1024a 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>. + * + * @see <a href="http://www.iro.umontreal.ca/~panneton/WELLRNG.html">WELL Random number + * generator</a> + * @since 2.2 + */ +public class Well1024a extends AbstractWell { + + /** Serializable version identifier. */ + private static final long serialVersionUID = 5680173464174485492L; + + /** Number of bits in the pool. */ + private static final int K = 1024; + + /** First parameter of the algorithm. */ + private static final int M1 = 3; + + /** Second parameter of the algorithm. */ + private static final int M2 = 24; + + /** Third parameter of the algorithm. */ + private static final int M3 = 10; + + /** + * Creates a new random number generator. + * + * <p>The instance is initialized using the current time as the seed. + */ + public Well1024a() { + 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 Well1024a(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 Well1024a(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 Well1024a(long seed) { + super(K, M1, M2, M3, seed); + } + + /** {@inheritDoc} */ + @Override + protected int next(final int bits) { + + final int indexRm1 = iRm1[index]; + + final int v0 = v[index]; + final int vM1 = v[i1[index]]; + final int vM2 = v[i2[index]]; + final int vM3 = v[i3[index]]; + + final int z0 = v[indexRm1]; + final int z1 = v0 ^ (vM1 ^ (vM1 >>> 8)); + final int z2 = (vM2 ^ (vM2 << 19)) ^ (vM3 ^ (vM3 << 14)); + final int z3 = z1 ^ z2; + final int z4 = (z0 ^ (z0 << 11)) ^ (z1 ^ (z1 << 7)) ^ (z2 ^ (z2 << 13)); + + v[index] = z3; + v[indexRm1] = z4; + index = indexRm1; + + return z4 >>> (32 - bits); + } +} |