-/* 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;
+enum xbt_random_implem { XBT_RNG_xbt, XBT_RNG_std };
+static xbt_random_implem rng_implem = XBT_RNG_xbt;
+
+static std::mt19937 mt19937_gen;
+
+void set_implem_xbt()
+{
+ rng_implem = XBT_RNG_xbt;
+}
+void set_implem_std()
+{
+ rng_implem = XBT_RNG_std;
+}
+void set_mersenne_seed(int seed)
+{
+ mt19937_gen.seed(seed);
+}
int uniform_int(int min, int max)
{
- unsigned long gmin = mt19937_gen.min();
- unsigned long gmax = mt19937_gen.max();
- unsigned long grange = gmax - gmin + 1;
- unsigned long range = max - min + 1;
- xbt_assert(range < grange || range == grange, "The current implementation of the uniform integer distribution does "
- "not allow range to be higher than mt19937's range");
- unsigned long mult = grange / range;
- unsigned long maxallowed = gmin + (mult + 1) * range - 1;
- while (true) {
- unsigned long value = mt19937_gen();
- if (value > maxallowed) {
- } else {
- return value % range + min;
+ if (rng_implem == XBT_RNG_std) {
+ std::uniform_int_distribution<> dist(min, max);
+ return dist(mt19937_gen);
}
- }
+
+ unsigned long range = max - min + 1;
+ unsigned long value = mt19937_gen();
+ 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 value % range + min;
}
double uniform_real(double min, double max)
{
+ if (rng_implem == XBT_RNG_std) {
+ std::uniform_real_distribution<> dist(min, max);
+ return dist(mt19937_gen);
+ }
+
// 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();
double exponential(double lambda)
{
- unsigned long numerator = mt19937_gen() - mt19937_gen.min();
- unsigned long divisor = mt19937_gen.max() - mt19937_gen.min();
- return -1 / lambda * log(numerator / divisor);
+ if (rng_implem == XBT_RNG_std) {
+ std::exponential_distribution<> dist(lambda);
+ return dist(mt19937_gen);
+ }
+
+ return -1 / lambda * log(uniform_real(0, 1));
}
double normal(double mean, double sd)
{
- unsigned long numeratorA = mt19937_gen() - mt19937_gen.min();
- unsigned long numeratorB = mt19937_gen() - mt19937_gen.min();
- unsigned long divisor = mt19937_gen.max() - mt19937_gen.min();
- double u1 = numeratorA / divisor;
+ if (rng_implem == XBT_RNG_std) {
+ std::normal_distribution<> dist(mean, sd);
+ return dist(mt19937_gen);
+ }
+
+ double u1 = 0;
while (u1 < std::numeric_limits<double>::min()) {
- numeratorA = mt19937_gen() - mt19937_gen.min();
- u1 = numeratorA / divisor;
+ u1 = uniform_real(0, 1);
}
- double z0 = sqrt(-2.0 * log(numeratorA / divisor)) * cos(2 * M_PI * numeratorB / divisor);
+ double u2 = uniform_real(0, 1);
+ double z0 = sqrt(-2.0 * log(u1)) * cos(2 * M_PI * u2);
return z0 * sd + mean;
}