1/**
2 * Copyright (c) Glow Contributors. See CONTRIBUTORS file.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16#ifndef GLOW_SUPPORT_RANDOM_H
17#define GLOW_SUPPORT_RANDOM_H
18
19#include <random>
20
21namespace glow {
22
23/// A pseudo-random number generator.
24///
25/// A PseudoRNG generates a deterministic sequence of numbers controlled by the
26/// initial seed. Use the various templates from the <random> standard library
27/// header to draw numbers from a specific distribution.
28class PseudoRNG {
29public:
30 /// Glow uses the Mersenne Twister engine.
31 typedef std::mt19937 Engine;
32
33private:
34 Engine engine_;
35
36public:
37 /// Get a freshly initialized pseudo-random number generator.
38 ///
39 /// All the generators created by this default constructor will generate the
40 /// same deterministic sequence of numbers, controlled by the
41 /// "-pseudo-random-seed" command line option.
42 PseudoRNG();
43
44 /// \returns a pseudo-random floating point number from the half-open range
45 /// [-1; 1).
46 double nextRand();
47
48 /// \returns a pseudo-random floating point number from the half-open
49 /// user-specified range [a; b).
50 double nextRandReal(double a, double b);
51
52 /// \returns the next uniform random integer in the closed interval [a, b].
53 int nextRandInt(int a, int b) {
54 return std::uniform_int_distribution<int>(a, b)(engine_);
55 }
56
57 /// This typedef and the methods below implement the standard interface for a
58 /// random number generator.
59 typedef Engine::result_type result_type;
60 /// \returns the next pseudo-random number between min() and max().
61 result_type operator()() { return engine_(); }
62 /// \returns the smallest possible value generated.
63 static constexpr result_type min() { return Engine::min(); }
64 /// \returns the largest possible value generated.
65 static constexpr result_type max() { return Engine::max(); }
66};
67
68} // namespace glow
69
70#endif // GLOW_SUPPORT_RANDOM_H
71