/*
* 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 WELL19937c 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>
* @since 2.2
*/
public class Well19937c extends AbstractWell {
/** Serializable version identifier. */
private static final long serialVersionUID = -7203498180754925124L;
/** Number of bits in the pool. */
private static final int K = 19937;
/** First parameter of the algorithm. */
private static final int M1 = 70;
/** Second parameter of the algorithm. */
private static final int M2 = 179;
/** Third parameter of the algorithm. */
private static final int M3 = 449;
/** Creates a new random number generator.
* <p>The instance is initialized using the current time as the
* seed.</p>
*/
public Well19937c() {
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 Well19937c(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 Well19937c(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 Well19937c(long seed) {
super(K, M1, M2, M3, seed);
}
/** {@inheritDoc} */
@Override
protected int next(final int bits) {
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]];
final int z0 = (0x80000000 & v[indexRm1]) ^ (0x7FFFFFFF & v[indexRm2]);
final int z1 = (v0 ^ (v0 << 25)) ^ (vM1 ^ (vM1 >>> 27));
final int z2 = (vM2 >>> 9) ^ (vM3 ^ (vM3 >>> 1));
final int z3 = z1 ^ z2;
int z4 = z0 ^ (z1 ^ (z1 << 9)) ^ (z2 ^ (z2 << 21)) ^ (z3 ^ (z3 >>> 21));
v[index] = z3;
v[indexRm1] = z4;
v[indexRm2] &= 0x80000000;
index = indexRm1;
// add Matsumoto-Kurita tempering
// to get a maximally-equidistributed generator
z4 ^= (z4 << 7) & 0xe46e1700;
z4 ^= (z4 << 15) & 0x9b868000;
return z4 >>> (32 - bits);
}
}