| /* |
| * 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.rng.core.source32; |
| |
| import java.util.Arrays; |
| import org.apache.commons.rng.core.util.NumberFactory; |
| |
| /** |
| * This abstract class implements the WELL class of 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 1.0 |
| */ |
| public abstract class AbstractWell extends IntProvider { |
| /** Block size. */ |
| private static final int BLOCK_SIZE = 32; |
| /** Current index in the bytes pool. */ |
| protected int index; |
| /** Bytes pool. */ |
| protected final int[] v; |
| |
| /** |
| * Creates an instance with the given {@code seed}. |
| * |
| * @param k Number of bits in the pool (not necessarily a multiple of 32). |
| * @param seed Initial seed. |
| */ |
| protected AbstractWell(final int k, |
| final int[] seed) { |
| final int r = calculateBlockCount(k); |
| v = new int[r]; |
| index = 0; |
| |
| // Initialize the pool content. |
| setSeedInternal(seed); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| protected byte[] getStateInternal() { |
| final int[] s = Arrays.copyOf(v, v.length + 1); |
| s[v.length] = index; |
| |
| return composeStateInternal(NumberFactory.makeByteArray(s), |
| super.getStateInternal()); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| protected void setStateInternal(byte[] s) { |
| final byte[][] c = splitStateInternal(s, (v.length + 1) * 4); |
| |
| final int[] tmp = NumberFactory.makeIntArray(c[0]); |
| System.arraycopy(tmp, 0, v, 0, v.length); |
| index = tmp[v.length]; |
| |
| super.setStateInternal(c[1]); |
| } |
| |
| /** |
| * Initializes the generator with the given {@code seed}. |
| * |
| * @param seed Seed. Cannot be null. |
| */ |
| private void setSeedInternal(final int[] seed) { |
| System.arraycopy(seed, 0, v, 0, Math.min(seed.length, v.length)); |
| |
| if (seed.length < v.length) { |
| for (int i = seed.length; i < v.length; ++i) { |
| final long current = v[i - seed.length]; |
| v[i] = (int) ((1812433253L * (current ^ (current >> 30)) + i) & 0xffffffffL); |
| } |
| } |
| |
| index = 0; |
| } |
| |
| /** |
| * Calculate the number of 32-bits blocks. |
| * |
| * @param k Number of bits in the pool (not necessarily a multiple of 32). |
| * @return the number of 32-bits blocks. |
| */ |
| private static int calculateBlockCount(final int k) { |
| // The bits pool contains k bits, k = r w - p where r is the number |
| // of w bits blocks, w is the block size (always 32 in the original paper) |
| // and p is the number of unused bits in the last block. |
| return (k + BLOCK_SIZE - 1) / BLOCK_SIZE; |
| } |
| |
| /** |
| * Inner class used to store the indirection index table which is fixed for a given |
| * type of WELL class of pseudo-random number generator. |
| */ |
| protected static final class IndexTable { |
| /** Index indirection table giving for each index its predecessor taking table size into account. */ |
| private final int[] iRm1; |
| /** Index indirection table giving for each index its second predecessor taking table size into account. */ |
| private final int[] iRm2; |
| /** Index indirection table giving for each index the value index + m1 taking table size into account. */ |
| private final int[] i1; |
| /** Index indirection table giving for each index the value index + m2 taking table size into account. */ |
| private final int[] i2; |
| /** Index indirection table giving for each index the value index + m3 taking table size into account. */ |
| private final int[] i3; |
| |
| /** Creates a new pre-calculated indirection index table. |
| * @param k number of bits in the pool (not necessarily a multiple of 32) |
| * @param m1 first parameter of the algorithm |
| * @param m2 second parameter of the algorithm |
| * @param m3 third parameter of the algorithm |
| */ |
| public IndexTable(final int k, final int m1, final int m2, final int m3) { |
| |
| final int r = calculateBlockCount(k); |
| |
| // precompute indirection index tables. These tables are used for optimizing access |
| // they allow saving computations like "(j + r - 2) % r" with costly modulo operations |
| iRm1 = new int[r]; |
| iRm2 = new int[r]; |
| i1 = new int[r]; |
| i2 = new int[r]; |
| i3 = new int[r]; |
| for (int j = 0; j < r; ++j) { |
| iRm1[j] = (j + r - 1) % r; |
| iRm2[j] = (j + r - 2) % r; |
| i1[j] = (j + m1) % r; |
| i2[j] = (j + m2) % r; |
| i3[j] = (j + m3) % r; |
| } |
| } |
| |
| /** |
| * Returns the predecessor of the given index modulo the table size. |
| * @param index the index to look at |
| * @return (index - 1) % table size |
| */ |
| public int getIndexPred(final int index) { |
| return iRm1[index]; |
| } |
| |
| /** |
| * Returns the second predecessor of the given index modulo the table size. |
| * @param index the index to look at |
| * @return (index - 2) % table size |
| */ |
| public int getIndexPred2(final int index) { |
| return iRm2[index]; |
| } |
| |
| /** |
| * Returns index + M1 modulo the table size. |
| * @param index the index to look at |
| * @return (index + M1) % table size |
| */ |
| public int getIndexM1(final int index) { |
| return i1[index]; |
| } |
| |
| /** |
| * Returns index + M2 modulo the table size. |
| * @param index the index to look at |
| * @return (index + M2) % table size |
| */ |
| public int getIndexM2(final int index) { |
| return i2[index]; |
| } |
| |
| /** |
| * Returns index + M3 modulo the table size. |
| * @param index the index to look at |
| * @return (index + M3) % table size |
| */ |
| public int getIndexM3(final int index) { |
| return i3[index]; |
| } |
| } |
| } |