001 /*
002 * Java Genetic Algorithm Library (jenetics-1.6.0).
003 * Copyright (c) 2007-2014 Franz Wilhelmstötter
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 *
017 * Author:
018 * Franz Wilhelmstötter (franz.wilhelmstoetter@gmx.at)
019 */
020 package org.jenetics.util;
021
022 import static java.lang.Math.min;
023
024 import java.util.Random;
025
026 import org.jenetics.internal.math.random;
027
028 /**
029 * An abstract base class which eases the implementation of {@code Random}
030 * objects which natively creates random {@code long} values. All other
031 * {@code Random} functions are optimized using this {@code long} values.
032 *
033 * [code]
034 * public class MyRandom64 extends Random64 {
035 * \@Override
036 * public long nextLong() {
037 * // Only this method must be implemented.
038 * ...
039 * }
040 * }
041 * [/code]
042 *
043 * @author <a href="mailto:franz.wilhelmstoetter@gmx.at">Franz Wilhelmstötter</a>
044 * @since 1.3
045 * @version 1.3 — <em>$Date: 2014-02-15 $</em>
046 */
047 public abstract class Random64 extends PRNG {
048
049 private static final long serialVersionUID = 1L;
050
051 private static final int LONG_BYTE_SIZE = 8;
052
053 protected Random64(long seed) {
054 super(seed);
055 }
056
057 protected Random64() {
058 this(math.random.seed());
059 }
060
061 /**
062 * Force to explicitly override the Random.nextLong() method. All other
063 * methods of this class are implemented by calling this method.
064 */
065 @Override
066 public abstract long nextLong();
067
068
069 @Override
070 public boolean nextBoolean() {
071 return (nextLong() & 0x8000000000000000L) != 0L;
072 }
073
074 @Override
075 public int nextInt() {
076 return (int)(nextLong() >>> Integer.SIZE);
077 }
078
079 @Override
080 protected int next(final int bits) {
081 return (int)(nextLong() >>> (Long.SIZE - bits));
082 }
083
084 /**
085 * Optimized version of the {@link Random#nextBytes(byte[])} method for
086 * 64-bit random engines.
087 */
088 @Override
089 public void nextBytes(final byte[] bytes) {
090 for (int i = 0, len = bytes.length; i < len;) {
091 int n = min(len - i, LONG_BYTE_SIZE);
092
093 for (long x = nextLong(); --n >= 0; x >>= Byte.SIZE) {
094 bytes[i++] = (byte)x;
095 }
096 }
097 }
098
099 @Override
100 public float nextFloat() {
101 return random.toFloat2(nextLong());
102 }
103
104 /**
105 * Optimized version of the {@link Random#nextDouble()} method for 64-bit
106 * random engines.
107 */
108 @Override
109 public double nextDouble() {
110 return random.toDouble2(nextLong());
111 }
112
113 }
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