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/*
* 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;
/** This class implements the WELL512a 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 class Well512a extends AbstractWell {
/** Serializable version identifier. */
private static final long serialVersionUID = -6104179812103820574L;
/** Number of bits in the pool. */
private static final int K = 512;
/** First parameter of the algorithm. */
private static final int M1 = 13;
/** Second parameter of the algorithm. */
private static final int M2 = 9;
/** Third parameter of the algorithm. */
private static final int M3 = 5;
/** Creates a new random number generator.
* <p>The instance is initialized using the current time as the
* seed.</p>
*/
public Well512a() {
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 Well512a(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 Well512a(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 Well512a(long seed) {
super(K, M1, M2, M3, seed);
}
/** {@inheritDoc} */
@Override
protected int next(final int bits) {
final int indexRm1 = iRm1[index];
final int vi = v[index];
final int vi1 = v[i1[index]];
final int vi2 = v[i2[index]];
final int z0 = v[indexRm1];
// the values below include the errata of the original article
final int z1 = (vi ^ (vi << 16)) ^ (vi1 ^ (vi1 << 15));
final int z2 = vi2 ^ (vi2 >>> 11);
final int z3 = z1 ^ z2;
final int z4 = (z0 ^ (z0 << 2)) ^ (z1 ^ (z1 << 18)) ^ (z2 << 28) ^ (z3 ^ ((z3 << 5) & 0xda442d24));
v[index] = z3;
v[indexRm1] = z4;
index = indexRm1;
return z4 >>> (32 - bits);
}
}
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