-/* Copyright (c) 2019. The SimGrid Team. All rights reserved. */
+/* Copyright (c) 2019-2020. The SimGrid Team. All rights reserved. */
/* This program is free software; you can redistribute it and/or modify it
* under the terms of the license (GNU LGPL) which comes with this package. */
namespace simgrid {
namespace xbt {
namespace random {
-std::mt19937 mt19937_gen;
-xbt_random_method current_rng = XBT_RNG_xbt;
+enum xbt_random_implem { XBT_RNG_xbt, XBT_RNG_std };
+static xbt_random_implem rng_implem = XBT_RNG_xbt;
-void use_xbt()
+static std::mt19937 mt19937_gen;
+
+void set_implem_xbt()
{
- current_rng = XBT_RNG_xbt;
+ rng_implem = XBT_RNG_xbt;
}
-void use_std()
+void set_implem_std()
{
- current_rng = XBT_RNG_std;
+ rng_implem = XBT_RNG_std;
+}
+void set_mersenne_seed(int seed)
+{
+ mt19937_gen.seed(seed);
}
int uniform_int(int min, int max)
{
- switch (current_rng) {
- case XBT_RNG_xbt:
- return xbt_uniform_int(min, max);
- case XBT_RNG_std: {
- std::uniform_int_distribution<> dist(min, max);
- return dist(mt19937_gen);
- }
- default:
- xbt_assert(false, "The uniform integer distribution is not yet supported for the current RNG.");
+ if (rng_implem == XBT_RNG_std) {
+ std::uniform_int_distribution<> dist(min, max);
+ return dist(mt19937_gen);
}
-}
-int xbt_uniform_int(int min, int max)
-{
unsigned long range = max - min + 1;
+ unsigned long value = mt19937_gen();
+ xbt_assert(min <= max,
+ "The minimum value for the uniform integer distribution must not be greater than the maximum value");
xbt_assert(range > 0, "Overflow in the uniform integer distribution, please use a smaller range.");
- xbt_assert(
- min <= max,
- "The maximum value for the uniform integer distribution must be greater than or equal to the minimum value");
- return min + (int)(range * xbt_uniform_real(0, 1));
+ while (value >= decltype(mt19937_gen)::max() - decltype(mt19937_gen)::max() % range) {
+ value = mt19937_gen();
+ }
+ return value % range + min;
}
double uniform_real(double min, double max)
{
- switch (current_rng) {
- case XBT_RNG_xbt:
- return xbt_uniform_real(min, max);
- case XBT_RNG_std: {
- std::uniform_real_distribution<> dist(min, max);
- return dist(mt19937_gen);
- }
- default:
- xbt_assert(false, "The uniform real distribution is not yet supported for the current RNG.");
+ if (rng_implem == XBT_RNG_std) {
+ std::uniform_real_distribution<> dist(min, max);
+ return dist(mt19937_gen);
}
-}
-double xbt_uniform_real(double min, double max)
-{
// This reuses Boost's uniform real distribution ideas
- unsigned long numerator = mt19937_gen() - mt19937_gen.min();
- unsigned long divisor = mt19937_gen.max() - mt19937_gen.min();
+ 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) * numerator / divisor;
}
double exponential(double lambda)
{
- switch (current_rng) {
- case XBT_RNG_xbt:
- return xbt_exponential(lambda);
- case XBT_RNG_std: {
- std::exponential_distribution<> dist(lambda);
- return dist(mt19937_gen);
- }
- default:
- xbt_assert(false, "The exponential distribution is not yet supported for the current RNG.");
+ if (rng_implem == XBT_RNG_std) {
+ std::exponential_distribution<> dist(lambda);
+ return dist(mt19937_gen);
}
-}
-double xbt_exponential(double lambda)
-{
- return -1 / lambda * log(uniform_real(0, 1));
+ return -1.0 / lambda * log(uniform_real(0.0, 1.0));
}
double normal(double mean, double sd)
{
- switch (current_rng) {
- case XBT_RNG_xbt:
- return xbt_normal(mean, sd);
- case XBT_RNG_std: {
- std::normal_distribution<> dist(mean, sd);
- return dist(mt19937_gen);
- }
- default:
- xbt_assert(false, "The normal distribution is not yet supported for the curent RNG.");
+ if (rng_implem == XBT_RNG_std) {
+ std::normal_distribution<> dist(mean, sd);
+ return dist(mt19937_gen);
}
-}
-double xbt_normal(double mean, double sd)
-{
- double u1 = 0;
+ double u1 = 0.0;
while (u1 < std::numeric_limits<double>::min()) {
- u1 = uniform_real(0, 1);
+ u1 = uniform_real(0.0, 1.0);
}
- double u2 = uniform_real(0, 1);
- double z0 = sqrt(-2.0 * log(u1)) * cos(2 * M_PI * u2);
+ 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;
}
-void set_mersenne_seed(int seed)
-{
- mt19937_gen.seed(seed);
-}
-
} // namespace random
} // namespace xbt
} // namespace simgrid
