+bool Random::read_state(const std::string& filename)
+{
+ std::ifstream file(filename);
+ file >> mt19937_gen;
+ file.close();
+ if (file.fail())
+ XBT_WARN("Could not save the RNG state to file %s.", filename.c_str());
+ return not file.fail();
+}
+
+bool Random::write_state(const std::string& filename) const
+{
+ std::ofstream file(filename);
+ file << mt19937_gen;
+ file.close();
+ if (file.fail())
+ XBT_WARN("Could not read the RNG state from file %s.", filename.c_str());
+ return not file.fail();
+}
+
+int StdRandom::uniform_int(int min, int max)
+{
+ std::uniform_int_distribution<> dist(min, max);
+ return dist(mt19937_gen);
+}
+
+double StdRandom::uniform_real(double min, double max)
+{
+ std::uniform_real_distribution<> dist(min, max);
+ return dist(mt19937_gen);
+}
+
+double StdRandom::exponential(double lambda)
+{
+ std::exponential_distribution<> dist(lambda);
+ return dist(mt19937_gen);
+}
+
+double StdRandom::normal(double mean, double sd)
+{
+ std::normal_distribution<> dist(mean, sd);
+ return dist(mt19937_gen);
+}
+
+int XbtRandom::uniform_int(int min, int max)
+{
+ // The casts to unsigned are here to ensure that the value of range is correctly calculated, even when greater than
+ // INT_MAX. See the corresponding unit tests for examples.
+ unsigned long range = static_cast<unsigned>(max) - static_cast<unsigned>(min);
+ xbt_assert(min <= max,
+ "The minimum value for the uniform integer distribution must not be greater than the maximum value");
+ xbt_assert(range <= decltype(mt19937_gen)::max(),
+ "Overflow in the uniform integer distribution, please use a smaller range.");
+ if (range == decltype(mt19937_gen)::max())
+ return static_cast<int>(mt19937_gen() + min);
+
+ ++range;
+ unsigned long limit = decltype(mt19937_gen)::max() - decltype(mt19937_gen)::max() % range;
+ unsigned long value;
+ do {
+ value = mt19937_gen();
+ } while (value >= limit);
+ return static_cast<int>(value % range + min);
+}
+
+double XbtRandom::uniform_real(double min, double max)
+{
+ // This reuses Boost's uniform real distribution ideas
+ constexpr unsigned long divisor = decltype(mt19937_gen)::max() - decltype(mt19937_gen)::min();
+ unsigned long numerator;
+ do {
+ numerator = mt19937_gen() - decltype(mt19937_gen)::min();
+ } while (numerator == divisor);
+ return min + (max - min) * static_cast<double>(numerator) / divisor;
+}
+
+double XbtRandom::exponential(double lambda)
+{
+ return -1.0 / lambda * log(uniform_real(0.0, 1.0));
+}
+
+double XbtRandom::normal(double mean, double sd)
+{
+ double u1;
+ do {
+ u1 = uniform_real(0.0, 1.0);
+ } while (u1 < std::numeric_limits<double>::min());
+ double u2 = uniform_real(0.0, 1.0);
+ double z0 = sqrt(-2.0 * log(u1)) * cos(2.0 * M_PI * u2);
+ return z0 * sd + mean;
+}
+
+static std::unique_ptr<Random> default_random = std::make_unique<XbtRandom>();