#include "xbt/random.hpp"
#include "xbt/asserts.h"
+#include <limits>
#include <random>
namespace simgrid {
namespace xbt {
namespace random {
std::mt19937 mt19937_gen;
+xbt_random_method current_rng = XBT_RNG_xbt;
+
+void use_xbt()
+{
+ current_rng = XBT_RNG_xbt;
+}
+void use_std()
+{
+ current_rng = XBT_RNG_std;
+}
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;
+ 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.");
}
}
+int xbt_uniform_int(int min, int max)
+{
+ unsigned long range = max - min + 1;
+ 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));
+}
+
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.");
+ }
+}
+
+double xbt_uniform_real(double min, double max)
{
// This reuses Boost's uniform real distribution ideas
unsigned long numerator = mt19937_gen() - 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);
+ 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.");
+ }
+}
+
+double xbt_exponential(double lambda)
+{
+ 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;
- while (u1 < DBL_MIN) {
- numeratorA = mt19937_gen() - mt19937_gen.min();
- u1 = numeratorA / divisor;
+ 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.");
}
- double z0 = sqrt(-2.0 * log(numeratorA / divisor)) * cos(2 * M_PI * numeratorB / divisor);
+}
+
+double xbt_normal(double mean, double sd)
+{
+ double u1 = 0;
+ while (u1 < std::numeric_limits<double>::min()) {
+ u1 = uniform_real(0, 1);
+ }
+ double u2 = uniform_real(0, 1);
+ double z0 = sqrt(-2.0 * log(u1)) * cos(2 * M_PI * u2);
return z0 * sd + mean;
}
+void set_mersenne_seed(int seed)
+{
+ mt19937_gen.seed(seed);
+}
+
} // namespace random
} // namespace xbt
} // namespace simgrid
