1 /* Copyright (c) 2019-2020. 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");
22 bool Random::read_state(const std::string& filename)
24 std::ifstream file(filename);
28 XBT_WARN("Could not save the RNG state to file %s.", filename.c_str());
29 return not file.fail();
32 bool Random::write_state(const std::string& filename) const
34 std::ofstream file(filename);
38 XBT_WARN("Could not read the RNG state from file %s.", filename.c_str());
39 return not file.fail();
42 int StdRandom::uniform_int(int min, int max)
44 std::uniform_int_distribution<> dist(min, max);
45 return dist(mt19937_gen);
48 double StdRandom::uniform_real(double min, double max)
50 std::uniform_real_distribution<> dist(min, max);
51 return dist(mt19937_gen);
54 double StdRandom::exponential(double lambda)
56 std::exponential_distribution<> dist(lambda);
57 return dist(mt19937_gen);
60 double StdRandom::normal(double mean, double sd)
62 std::normal_distribution<> dist(mean, sd);
63 return dist(mt19937_gen);
66 int XbtRandom::uniform_int(int min, int max)
68 unsigned long range = max - min + 1;
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 > 0, "Overflow in the uniform integer distribution, please use a smaller range.");
74 value = mt19937_gen();
75 } while (value >= decltype(mt19937_gen)::max() - decltype(mt19937_gen)::max() % range);
76 return static_cast<int>(value % range + min);
79 double XbtRandom::uniform_real(double min, double max)
81 // This reuses Boost's uniform real distribution ideas
82 constexpr unsigned long divisor = decltype(mt19937_gen)::max() - decltype(mt19937_gen)::min();
83 unsigned long numerator;
85 numerator = mt19937_gen() - decltype(mt19937_gen)::min();
86 } while (numerator == divisor);
87 return min + (max - min) * static_cast<double>(numerator) / divisor;
90 double XbtRandom::exponential(double lambda)
92 return -1.0 / lambda * log(uniform_real(0.0, 1.0));
95 double XbtRandom::normal(double mean, double sd)
99 u1 = uniform_real(0.0, 1.0);
100 } while (u1 < std::numeric_limits<double>::min());
101 double u2 = uniform_real(0.0, 1.0);
102 double z0 = sqrt(-2.0 * log(u1)) * cos(2.0 * M_PI * u2);
103 return z0 * sd + mean;
106 static std::unique_ptr<Random> default_random = std::make_unique<XbtRandom>();
108 void set_implem_xbt()
110 default_random = std::make_unique<XbtRandom>();
112 void set_implem_std()
114 default_random = std::make_unique<StdRandom>();
117 void set_mersenne_seed(int seed)
119 default_random->set_seed(seed);
122 bool read_mersenne_state(const std::string& filename)
124 return default_random->read_state(filename);
127 bool write_mersenne_state(const std::string& filename)
129 return default_random->write_state(filename);
132 int uniform_int(int min, int max)
134 return default_random->uniform_int(min, max);
137 double uniform_real(double min, double max)
139 return default_random->uniform_real(min, max);
142 double exponential(double lambda)
144 return default_random->exponential(lambda);
147 double normal(double mean, double sd)
149 return default_random->normal(mean, sd);
152 } // namespace random
154 } // namespace simgrid