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
getUint64(void)52 deUint64 getUint64 (void) { deUint32 upper = getUint32(); return (deUint64)upper << 32ull | (deUint64)getUint32(); }
getUint32(void)53 deUint32 getUint32 (void) { return deRandom_getUint32(&m_rnd); }
getUint16(void)54 deUint16 getUint16 (void) { return (deUint16)deRandom_getUint32(&m_rnd); }
getUint8(void)55 deUint8 getUint8 (void) { return (deUint8)deRandom_getUint32(&m_rnd); }
56
57 template <class InputIter, class OutputIter>
58 void choose (InputIter first, InputIter last, OutputIter result, int numItems);
59
60 template <typename T, class InputIter>
61 T choose (InputIter first, InputIter last);
62
63 // \note Weights must be floats
64 template <typename T, class InputIter, class WeightIter>
65 T chooseWeighted (InputIter first, InputIter last, WeightIter weight);
66
67 template <class Iterator>
68 void shuffle (Iterator first, Iterator last);
69
70 bool operator== (const Random& other) const;
71 bool operator!= (const Random& other) const;
72
73 private:
74 deRandom m_rnd;
75 } DE_WARN_UNUSED_TYPE;
76
77 // Inline implementations
78
getFloat(float min,float max)79 inline float Random::getFloat (float min, float max)
80 {
81 DE_ASSERT(min <= max);
82 return min + (max-min)*getFloat();
83 }
84
getDouble(double min,double max)85 inline double Random::getDouble (double min, double max)
86 {
87 DE_ASSERT(min <= max);
88 return min + (max-min)*getDouble();
89 }
90
getInt(int min,int max)91 inline int Random::getInt (int min, int max)
92 {
93 DE_ASSERT(min <= max);
94 if (min == (int)0x80000000 && max == (int)0x7fffffff)
95 return (int)getUint32();
96 else
97 return min + (int)(getUint32() % (deUint32)(max-min+1));
98 }
99
100 // Template implementations
101
102 template <class InputIter, class OutputIter>
choose(InputIter first,InputIter last,OutputIter result,int numItems)103 void Random::choose (InputIter first, InputIter last, OutputIter result, int numItems)
104 {
105 // Algorithm: Reservoir sampling
106 // http://en.wikipedia.org/wiki/Reservoir_sampling
107 // \note Will not work for suffling an array. Use suffle() instead.
108
109 int ndx;
110 for (ndx = 0; first != last; ++first, ++ndx)
111 {
112 if (ndx < numItems)
113 *(result + ndx) = *first;
114 else
115 {
116 int r = getInt(0, ndx);
117 if (r < numItems)
118 *(result + r) = *first;
119 }
120 }
121
122 DE_ASSERT(ndx >= numItems);
123 }
124
125 template <typename T, class InputIter>
choose(InputIter first,InputIter last)126 T Random::choose (InputIter first, InputIter last)
127 {
128 T val = T();
129 DE_ASSERT(first != last);
130 choose(first, last, &val, 1);
131 return val;
132 }
133
134 template <typename T, class InputIter, class WeightIter>
chooseWeighted(InputIter first,InputIter last,WeightIter weight)135 T Random::chooseWeighted (InputIter first, InputIter last, WeightIter weight)
136 {
137 // Compute weight sum
138 float weightSum = 0.0f;
139 int ndx;
140 for (ndx = 0; (first + ndx) != last; ndx++)
141 weightSum += *(weight + ndx);
142
143 // Random point in 0..weightSum
144 float p = getFloat(0.0f, weightSum);
145
146 // Find item in range
147 InputIter lastNonZero = last;
148 float curWeight = 0.0f;
149 for (ndx = 0; (first + ndx) != last; ndx++)
150 {
151 float w = *(weight + ndx);
152
153 curWeight += w;
154
155 if (p < curWeight)
156 return *(first + ndx);
157 else if (w > 0.0f)
158 lastNonZero = first + ndx;
159 }
160
161 DE_ASSERT(lastNonZero != last);
162 return *lastNonZero;
163 }
164
165 template <class Iterator>
shuffle(Iterator first,Iterator last)166 void Random::shuffle (Iterator first, Iterator last)
167 {
168 using std::swap;
169
170 // Fisher-Yates suffle
171 int numItems = (int)std::distance(first, last);
172
173 for (int i = numItems-1; i >= 1; i--)
174 {
175 int j = getInt(0, i);
176 swap(*(first + i), *(first + j));
177 }
178 }
179
180 } // de
181
182 #endif // _DERANDOM_HPP
183