/*
 * 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 WELL44497b pseudo-random number generator from François Panneton, Pierre L'Ecuyer and Makoto Matsumoto.

This generator is described in a paper by François Panneton, Pierre L'Ecuyer and Makoto Matsumoto Improved Long-Period Generators Based on Linear Recurrences Modulo 2 ACM Transactions on Mathematical Software, 32, 1 (2006). The errata for the paper are in wellrng-errata.txt.

See Also:
Since:2.2
/** This class implements the WELL44497b pseudo-random number generator * from Fran&ccedil;ois Panneton, Pierre L'Ecuyer and Makoto Matsumoto. * <p>This generator is described in a paper by Fran&ccedil;ois 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> * @since 2.2 */
public class Well44497b extends AbstractWell {
Serializable version identifier.
/** Serializable version identifier. */
private static final long serialVersionUID = 4032007538246675492L;
Number of bits in the pool.
/** Number of bits in the pool. */
private static final int K = 44497;
First parameter of the algorithm.
/** First parameter of the algorithm. */
private static final int M1 = 23;
Second parameter of the algorithm.
/** Second parameter of the algorithm. */
private static final int M2 = 481;
Third parameter of the algorithm.
/** Third parameter of the algorithm. */
private static final int M3 = 229;
Creates a new random number generator.

The instance is initialized using the current time as the seed.

/** 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.
Params:
  • seed – the initial seed (32 bits integer)
/** 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.
Params:
  • seed – the initial seed (32 bits integers array), if null the seed of the generator will be related to the current time
/** 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.
Params:
  • seed – the initial seed (64 bits integer)
/** 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}
/** {@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 << 7) & 0x93dd1400; z4 ^= (z4 << 15) & 0xfa118000; return z4 >>> (32 - bits); } }