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 21 namespace 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. 28 class PseudoRNG { 29 public: 30 /// Glow uses the Mersenne Twister engine. 31 typedef std::mt19937 Engine; 32 33 private: 34 Engine engine_; 35 36 public: 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]. nextRandInt(int a,int 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(). operator()61 result_type operator()() { return engine_(); } 62 /// \returns the smallest possible value generated. min()63 static constexpr result_type min() { return Engine::min(); } 64 /// \returns the largest possible value generated. max()65 static constexpr result_type max() { return Engine::max(); } 66 }; 67 68 } // namespace glow 69 70 #endif // GLOW_SUPPORT_RANDOM_H 71