1 #ifndef _DERANDOM_HPP
2 #define _DERANDOM_HPP
3 /*-------------------------------------------------------------------------
4 * drawElements C++ Base Library
5 * -----------------------------
6 *
7 * Copyright 2014 The Android Open Source Project
8 *
9 * Licensed under the Apache License, Version 2.0 (the "License");
10 * you may not use this file except in compliance with the License.
11 * You may obtain a copy of the License at
12 *
13 * http://www.apache.org/licenses/LICENSE-2.0
14 *
15 * Unless required by applicable law or agreed to in writing, software
16 * distributed under the License is distributed on an "AS IS" BASIS,
17 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
18 * See the License for the specific language governing permissions and
19 * limitations under the License.
20 *
21 *//*!
22 * \file
23 * \brief Random number generator utilities.
24 *//*--------------------------------------------------------------------*/
25
26 #include "deDefs.hpp"
27 #include "deRandom.h"
28
29 #include <iterator> // std::distance()
30 #include <algorithm> // std::swap()
31
32 namespace de
33 {
34
35 //! Random self-test - compare returned values against hard-coded values.
36 void Random_selfTest (void);
37
38 class Random
39 {
40 public:
Random(deUint32 seed)41 Random (deUint32 seed) { deRandom_init(&m_rnd, seed); }
~Random(void)42 ~Random (void) {}
43
getFloat(void)44 float getFloat (void) { return deRandom_getFloat(&m_rnd); }
getDouble(void)45 double getDouble (void) { return deRandom_getDouble(&m_rnd); }
getBool(void)46 bool getBool (void) { return deRandom_getBool(&m_rnd) == DE_TRUE; }
47
48 float getFloat (float min, float max);
49 double getDouble (double min, double max);
50 int getInt (int min, int max);
51
getInt64(void)52 deInt64 getInt64 (void) { deUint32 upper = getUint32(); return static_cast<deInt64>((deUint64)upper << 32ull | (deUint64)getUint32() ); }
getUint64(void)53 deUint64 getUint64 (void) { deUint32 upper = getUint32(); return (deUint64)upper << 32ull | (deUint64)getUint32(); }
getInt32(void)54 deInt32 getInt32 (void) { return static_cast<deInt32>(getUint32()); }
getUint32(void)55 deUint32 getUint32 (void) { return deRandom_getUint32(&m_rnd); }
getUint16(void)56 deUint16 getUint16 (void) { return (deUint16)deRandom_getUint32(&m_rnd); }
getUint8(void)57 deUint8 getUint8 (void) { return (deUint8)deRandom_getUint32(&m_rnd); }
58
59 template <class InputIter, class OutputIter>
60 void choose (InputIter first, InputIter last, OutputIter result, int numItems);
61
62 template <typename T, class InputIter>
63 T choose (InputIter first, InputIter last);
64
65 // \note Weights must be floats
66 template <typename T, class InputIter, class WeightIter>
67 T chooseWeighted (InputIter first, InputIter last, WeightIter weight);
68
69 template <class Iterator>
70 void shuffle (Iterator first, Iterator last);
71
72 bool operator== (const Random& other) const;
73 bool operator!= (const Random& other) const;
74
75 private:
76 deRandom m_rnd;
77 } DE_WARN_UNUSED_TYPE;
78
79 // Inline implementations
80
getFloat(float min,float max)81 inline float Random::getFloat (float min, float max)
82 {
83 DE_ASSERT(min <= max);
84 return min + (max-min)*getFloat();
85 }
86
getDouble(double min,double max)87 inline double Random::getDouble (double min, double max)
88 {
89 DE_ASSERT(min <= max);
90 return min + (max-min)*getDouble();
91 }
92
getInt(int min,int max)93 inline int Random::getInt (int min, int max)
94 {
95 DE_ASSERT(min <= max);
96 if (min == (int)0x80000000 && max == (int)0x7fffffff)
97 return (int)getUint32();
98 else
99 return min + (int)(getUint32() % (deUint32)(max-min+1));
100 }
101
102 // Template implementations
103
104 template <class InputIter, class OutputIter>
choose(InputIter first,InputIter last,OutputIter result,int numItems)105 void Random::choose (InputIter first, InputIter last, OutputIter result, int numItems)
106 {
107 // Algorithm: Reservoir sampling
108 // http://en.wikipedia.org/wiki/Reservoir_sampling
109 // \note Will not work for suffling an array. Use suffle() instead.
110
111 int ndx;
112 for (ndx = 0; first != last; ++first, ++ndx)
113 {
114 if (ndx < numItems)
115 *(result + ndx) = *first;
116 else
117 {
118 int r = getInt(0, ndx);
119 if (r < numItems)
120 *(result + r) = *first;
121 }
122 }
123
124 DE_ASSERT(ndx >= numItems);
125 }
126
127 template <typename T, class InputIter>
choose(InputIter first,InputIter last)128 T Random::choose (InputIter first, InputIter last)
129 {
130 T val = T();
131 DE_ASSERT(first != last);
132 choose(first, last, &val, 1);
133 return val;
134 }
135
136 template <typename T, class InputIter, class WeightIter>
chooseWeighted(InputIter first,InputIter last,WeightIter weight)137 T Random::chooseWeighted (InputIter first, InputIter last, WeightIter weight)
138 {
139 // Compute weight sum
140 float weightSum = 0.0f;
141 int ndx;
142 for (ndx = 0; (first + ndx) != last; ndx++)
143 weightSum += *(weight + ndx);
144
145 // Random point in 0..weightSum
146 float p = getFloat(0.0f, weightSum);
147
148 // Find item in range
149 InputIter lastNonZero = last;
150 float curWeight = 0.0f;
151 for (ndx = 0; (first + ndx) != last; ndx++)
152 {
153 float w = *(weight + ndx);
154
155 curWeight += w;
156
157 if (p < curWeight)
158 return *(first + ndx);
159 else if (w > 0.0f)
160 lastNonZero = first + ndx;
161 }
162
163 DE_ASSERT(lastNonZero != last);
164 return *lastNonZero;
165 }
166
167 template <class Iterator>
shuffle(Iterator first,Iterator last)168 void Random::shuffle (Iterator first, Iterator last)
169 {
170 using std::swap;
171
172 // Fisher-Yates suffle
173 int numItems = (int)std::distance(first, last);
174
175 for (int i = numItems-1; i >= 1; i--)
176 {
177 int j = getInt(0, i);
178 swap(*(first + i), *(first + j));
179 }
180 }
181
182 template<typename T> T randomScalar (de::Random& rnd, T minValue, T maxValue);
randomScalar(de::Random & rnd,float minValue,float maxValue)183 template<> inline float randomScalar (de::Random& rnd, float minValue, float maxValue) { return rnd.getFloat(minValue, maxValue); }
randomScalar(de::Random & rnd,deInt32 minValue,deInt32 maxValue)184 template<> inline deInt32 randomScalar (de::Random& rnd, deInt32 minValue, deInt32 maxValue) { return rnd.getInt(minValue, maxValue); }
randomScalar(de::Random & rnd,deUint32 minValue,deUint32 maxValue)185 template<> inline deUint32 randomScalar (de::Random& rnd, deUint32 minValue, deUint32 maxValue) { if (minValue == 0 && maxValue == 0xffffffff) return rnd.getUint32();
186 return minValue + rnd.getUint32() % (maxValue - minValue + 1); }
randomScalar(de::Random & rnd,deInt16 minValue,deInt16 maxValue)187 template<> inline deInt16 randomScalar (de::Random& rnd, deInt16 minValue, deInt16 maxValue) { return (deInt16)rnd.getInt(minValue, maxValue); }
randomScalar(de::Random & rnd,deUint16 minValue,deUint16 maxValue)188 template<> inline deUint16 randomScalar (de::Random& rnd, deUint16 minValue, deUint16 maxValue) { return (deUint16)(minValue + rnd.getUint16() % (maxValue - minValue + 1)); }
randomScalar(de::Random & rnd,deInt8 minValue,deInt8 maxValue)189 template<> inline deInt8 randomScalar (de::Random& rnd, deInt8 minValue, deInt8 maxValue) { return (deInt8)rnd.getInt(minValue, maxValue); }
randomScalar(de::Random & rnd,deUint8 minValue,deUint8 maxValue)190 template<> inline deUint8 randomScalar (de::Random& rnd, deUint8 minValue, deUint8 maxValue) { return (deUint8)(minValue + rnd.getUint8() % (maxValue - minValue + 1)); }
191
192 } // de
193
194 #endif // _DERANDOM_HPP
195