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Random number generators, probability distributions, combinatorics and statistics for Java.
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// ============================================================================
// Copyright 2006-2012 Daniel W. Dyer
//
// Licensed 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.uncommons.maths.random;
import java.util.Random;
import java.util.concurrent.locks.ReentrantLock;
import org.uncommons.maths.binary.BinaryUtils;
/**
* Java port of the
* cellular
* automaton pseudorandom number generator developed by Tony Pasqualoni.
*
* NOTE: Instances of this class do not use the seeding mechanism inherited
* from {@link Random}. Calls to the {@link #setSeed(long)} method will have no
* effect. Instead the seed must be set by a constructor.
*
* @author Tony Pasqualoni (original C version)
* @author Daniel Dyer (Java port)
*/
public class CellularAutomatonRNG extends Random implements RepeatableRNG
{
private static final int SEED_SIZE_BYTES = 4;
private static final int AUTOMATON_LENGTH = 2056;
private static final int[] RNG_RULE =
{
100, 75, 16, 3, 229, 51, 197, 118, 24, 62, 198, 11, 141, 152, 241, 188,
2, 17, 71, 47, 179, 177, 126, 231, 202, 243, 59, 25, 77, 196, 30, 134,
199, 163, 34, 216, 21, 84, 37, 182, 224, 186, 64, 79, 225, 45, 143, 20,
48, 147, 209, 221, 125, 29, 99, 12, 46, 190, 102, 220, 80, 215, 242, 105,
15, 53, 0, 67, 68, 69, 70, 89, 109, 195, 170, 78, 210, 131, 42, 110,
181, 145, 40, 114, 254, 85, 107, 87, 72, 192, 90, 201, 162, 122, 86, 252,
94, 129, 98, 132, 193, 249, 156, 172, 219, 230, 153, 54, 180, 151, 83, 214,
123, 88, 164, 167, 116, 117, 7, 27, 23, 213, 235, 5, 65, 124, 60, 127,
236, 149, 44, 28, 58, 121, 191, 13, 250, 10, 232, 112, 101, 217, 183, 239,
8, 32, 228, 174, 49, 113, 247, 158, 106, 218, 154, 66, 226, 157, 50, 26,
253, 93, 205, 41, 133, 165, 61, 161, 187, 169, 6, 171, 81, 248, 56, 175,
246, 36, 178, 52, 57, 212, 39, 176, 184, 185, 245, 63, 35, 189, 206, 76,
104, 233, 194, 19, 43, 159, 108, 55, 200, 155, 14, 74, 244, 255, 222, 207,
208, 137, 128, 135, 96, 144, 18, 95, 234, 139, 173, 92, 1, 203, 115, 223,
130, 97, 91, 227, 146, 4, 31, 120, 211, 38, 22, 138, 140, 237, 238, 251,
240, 160, 142, 119, 73, 103, 166, 33, 148, 9, 111, 136, 168, 150, 82, 204,
100, 75, 16, 3, 229, 51, 197, 118, 24, 62, 198, 11, 141, 152, 241, 188,
2, 17, 71, 47, 179, 177, 126, 231, 202, 243, 59, 25, 77, 196, 30, 134,
199, 163, 34, 216, 21, 84, 37, 182, 224, 186, 64, 79, 225, 45, 143, 20,
48, 147, 209, 221, 125, 29, 99, 12, 46, 190, 102, 220, 80, 215, 242, 105,
15, 53, 0, 67, 68, 69, 70, 89, 109, 195, 170, 78, 210, 131, 42, 110,
181, 145, 40, 114, 254, 85, 107, 87, 72, 192, 90, 201, 162, 122, 86, 252,
94, 129, 98, 132, 193, 249, 156, 172, 219, 230, 153, 54, 180, 151, 83, 214,
123, 88, 164, 167, 116, 117, 7, 27, 23, 213, 235, 5, 65, 124, 60, 127,
236, 149, 44, 28, 58, 121, 191, 13, 250, 10, 232, 112, 101, 217, 183, 239,
8, 32, 228, 174, 49, 113, 247, 158, 106, 218, 154, 66, 226, 157, 50, 26,
253, 93, 205, 41, 133, 165, 61, 161, 187, 169, 6, 171, 81, 248, 56, 175,
246, 36, 178, 52, 57, 212, 39, 176, 184, 185, 245, 63, 35, 189, 206, 76,
104, 233, 194, 19, 43, 159, 108, 55, 200, 155, 14, 74, 244, 255, 222, 207,
208, 137, 128, 135, 96, 144, 18, 95, 234, 139, 173, 92, 1, 203, 115, 223,
130, 97, 91, 227, 146, 4, 31, 120, 211, 38, 22, 138, 140, 237, 238, 251,
240, 160, 142, 119, 73, 103, 166, 33, 148, 9, 111, 136, 168, 150, 82
};
private final byte[] seed;
private final int[] cells = new int[AUTOMATON_LENGTH];
// Lock to prevent concurrent modification of the RNG's internal state.
private final ReentrantLock lock = new ReentrantLock();
private int currentCellIndex = AUTOMATON_LENGTH - 1;
/**
* Creates a new RNG and seeds it using the default seeding strategy.
*/
public CellularAutomatonRNG()
{
this(DefaultSeedGenerator.getInstance().generateSeed(SEED_SIZE_BYTES));
}
/**
* Seed the RNG using the provided seed generation strategy.
* @param seedGenerator The seed generation strategy that will provide
* the seed value for this RNG.
* @throws SeedException If there is a problem generating a seed.
*/
public CellularAutomatonRNG(SeedGenerator seedGenerator) throws SeedException
{
this(seedGenerator.generateSeed(SEED_SIZE_BYTES));
}
/**
* Creates an RNG and seeds it with the specified seed data.
* @param seed The seed data used to initialise the RNG.
*/
public CellularAutomatonRNG(byte[] seed)
{
if (seed == null || seed.length != SEED_SIZE_BYTES)
{
throw new IllegalArgumentException("Cellular Automaton RNG requires a 32-bit (4-byte) seed.");
}
this.seed = seed.clone();
// Set initial cell states using seed.
cells[AUTOMATON_LENGTH - 1] = seed[0] + 128;
cells[AUTOMATON_LENGTH - 2] = seed[1] + 128;
cells[AUTOMATON_LENGTH - 3] = seed[2] + 128;
cells[AUTOMATON_LENGTH - 4] = seed[3] + 128;
int seedAsInt = BinaryUtils.convertBytesToInt(seed, 0);
if (seedAsInt != 0xFFFFFFFF)
{
seedAsInt++;
}
for (int i = 0; i < AUTOMATON_LENGTH - 4; i++)
{
cells[i] = 0x000000FF & (seedAsInt >> (i % 32));
}
// Evolve automaton before returning integers.
for (int i = 0; i < AUTOMATON_LENGTH * AUTOMATON_LENGTH / 4; i++)
{
next(32);
}
}
/**
* {@inheritDoc}
*/
@Override
public int next(int bits)
{
int result;
try
{
lock.lock();
// Set cell addresses using address of current cell.
int cellC = currentCellIndex - 1;
int cellB = cellC - 1;
int cellA = cellB - 1;
// Update cell states using rule table.
cells[currentCellIndex] = RNG_RULE[cells[cellC] + cells[currentCellIndex]];
cells[cellC] = RNG_RULE[cells[cellB] + cells[cellC]];
cells[cellB] = RNG_RULE[cells[cellA] + cells[cellB]];
// Update the state of cellA and shift current cell to the left by 4 bytes.
if (cellA == 0)
{
cells[cellA] = RNG_RULE[cells[cellA]];
currentCellIndex = AUTOMATON_LENGTH - 1;
}
else
{
cells[cellA] = RNG_RULE[cells[cellA - 1] + cells[cellA]];
currentCellIndex -= 4;
}
result = convertCellsToInt(cells, cellA);
}
finally
{
lock.unlock();
}
return result >>> (32 - bits);
}
/**
* {@inheritDoc}
*/
public byte[] getSeed()
{
return seed;
}
private static int convertCellsToInt(int[] cells, int offset)
{
return cells[offset]
+ (cells[offset + 1] << 8)
+ (cells[offset + 2] << 16)
+ (cells[offset + 3] << 24);
}
}
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