1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * https://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 /*
19 * This is not the original file distributed by the Apache Software Foundation
20 * It has been modified by the Hipparchus project
21 */
22
23 package org.hipparchus.random;
24
25 import org.hipparchus.exception.LocalizedCoreFormats;
26 import org.hipparchus.exception.MathIllegalArgumentException;
27 import org.hipparchus.util.FastMath;
28 import org.hipparchus.util.SinCos;
29
30 /**
31 * Base class with default implementations for common methods.
32 */
33 abstract class BaseRandomGenerator implements RandomGenerator {
34
35 /** Next gaussian. */
36 private double nextGaussian = Double.NaN;
37
38 /** {@inheritDoc} */
39 @Override
40 public void setSeed(int seed) {
41 setSeed(new int[] { seed });
42 }
43
44 /** {@inheritDoc} */
45 @Override
46 public void setSeed(long seed) {
47 setSeed(new int[] { (int) (seed >>> 32), (int) (seed & 0xffffffffL) });
48 }
49
50 /** {@inheritDoc} */
51 @Override
52 public int nextInt(int n) throws IllegalArgumentException {
53 if (n <= 0) {
54 throw new MathIllegalArgumentException(LocalizedCoreFormats.NUMBER_TOO_SMALL_BOUND_EXCLUDED,
55 n, 0);
56 }
57
58 if ((n & -n) == n) {
59 return (int) ((n * (long) (nextInt() >>> 1)) >> 31);
60 }
61 int bits;
62 int val;
63 do {
64 bits = nextInt() >>> 1;
65 val = bits % n;
66 } while (bits - val + (n - 1) < 0);
67 return val;
68 }
69
70 /** {@inheritDoc} */
71 @Override
72 public long nextLong(long n) {
73 if (n <= 0) {
74 throw new MathIllegalArgumentException(LocalizedCoreFormats.NUMBER_TOO_SMALL_BOUND_EXCLUDED,
75 n, 0);
76 }
77
78 long bits;
79 long val;
80 do {
81 bits = nextLong() >>> 1;
82 val = bits % n;
83 } while (bits - val + (n - 1) < 0);
84 return val;
85 }
86
87 /** {@inheritDoc} */
88 @Override
89 public double nextGaussian() {
90
91 final double random;
92 if (Double.isNaN(nextGaussian)) {
93 // generate a new pair of gaussian numbers
94 final double x = nextDouble();
95 final double y = nextDouble();
96 final double alpha = 2 * FastMath.PI * x;
97 final double r = FastMath.sqrt(-2 * FastMath.log(y));
98 final SinCos scAlpha = FastMath.sinCos(alpha);
99 random = r * scAlpha.cos();
100 nextGaussian = r * scAlpha.sin();
101 } else {
102 // use the second element of the pair already generated
103 random = nextGaussian;
104 nextGaussian = Double.NaN;
105 }
106
107 return random;
108
109 }
110
111 /**
112 * Clears the cache used by the default implementation of
113 * {@link #nextGaussian()}.
114 */
115 protected void clearCache() {
116 nextGaussian = Double.NaN;
117 }
118
119 /** {@inheritDoc} */
120 @Override
121 public String toString() {
122 return getClass().getName();
123 }
124
125 }