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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.math3.random;


/** This class implements the WELL1024a 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 WELL Random number generator * @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. *

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); } }




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