1 /* Copyright (c) 2019-2022. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
6 #include "xbt/asserts.h"
12 #include <xbt/log.hpp>
13 #include <xbt/random.hpp>
15 XBT_LOG_EXTERNAL_CATEGORY(xbt);
16 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(xbt_random, xbt, "Random");
18 namespace simgrid::xbt::random {
20 bool Random::read_state(const std::string& filename)
22 std::ifstream file(filename);
26 XBT_WARN("Could not save the RNG state to file %s.", filename.c_str());
27 return not file.fail();
30 bool Random::write_state(const std::string& filename) const
32 std::ofstream file(filename);
36 XBT_WARN("Could not read the RNG state from file %s.", filename.c_str());
37 return not file.fail();
40 int StdRandom::uniform_int(int min, int max)
42 std::uniform_int_distribution dist(min, max);
43 return dist(mt19937_gen);
46 double StdRandom::uniform_real(double min, double max)
48 std::uniform_real_distribution dist(min, max);
49 return dist(mt19937_gen);
52 double StdRandom::exponential(double lambda)
54 std::exponential_distribution dist(lambda);
55 return dist(mt19937_gen);
58 double StdRandom::normal(double mean, double sd)
60 std::normal_distribution dist(mean, sd);
61 return dist(mt19937_gen);
64 int XbtRandom::uniform_int(int min, int max)
66 // The casts to unsigned are here to ensure that the value of range is correctly calculated, even when greater than
67 // INT_MAX. See the corresponding unit tests for examples.
68 unsigned long range = static_cast<unsigned>(max) - static_cast<unsigned>(min);
69 xbt_assert(min <= max,
70 "The minimum value for the uniform integer distribution must not be greater than the maximum value");
71 xbt_assert(range <= decltype(mt19937_gen)::max(),
72 "Overflow in the uniform integer distribution, please use a smaller range.");
73 if (range == decltype(mt19937_gen)::max())
74 return static_cast<int>(mt19937_gen() + min);
77 unsigned long limit = decltype(mt19937_gen)::max() - decltype(mt19937_gen)::max() % range;
80 value = mt19937_gen();
81 } while (value >= limit);
82 return static_cast<int>(value % range + min);
85 double XbtRandom::uniform_real(double min, double max)
87 // This reuses Boost's uniform real distribution ideas
88 constexpr unsigned long divisor = decltype(mt19937_gen)::max() - decltype(mt19937_gen)::min();
89 unsigned long numerator;
91 numerator = mt19937_gen() - decltype(mt19937_gen)::min();
92 } while (numerator == divisor);
93 return min + (max - min) * static_cast<double>(numerator) / divisor;
96 double XbtRandom::exponential(double lambda)
98 return -1.0 / lambda * log(uniform_real(0.0, 1.0));
101 double XbtRandom::normal(double mean, double sd)
105 u1 = uniform_real(0.0, 1.0);
106 } while (u1 < std::numeric_limits<double>::min());
107 double u2 = uniform_real(0.0, 1.0);
108 double z0 = sqrt(-2.0 * log(u1)) * cos(2.0 * M_PI * u2);
109 return z0 * sd + mean;
112 static std::unique_ptr<Random> default_random = std::make_unique<XbtRandom>();
114 void set_implem_xbt()
116 default_random = std::make_unique<XbtRandom>();
118 void set_implem_std()
120 default_random = std::make_unique<StdRandom>();
123 void set_mersenne_seed(int seed)
125 default_random->set_seed(seed);
128 bool read_mersenne_state(const std::string& filename)
130 return default_random->read_state(filename);
133 bool write_mersenne_state(const std::string& filename)
135 return default_random->write_state(filename);
138 int uniform_int(int min, int max)
140 return default_random->uniform_int(min, max);
143 double uniform_real(double min, double max)
145 return default_random->uniform_real(min, max);
148 double exponential(double lambda)
150 return default_random->exponential(lambda);
153 double normal(double mean, double sd)
155 return default_random->normal(mean, sd);
158 } // namespace simgrid::xbt::random