#ifndef SIMGRID_XBT_RANDOM_HPP
#define SIMGRID_XBT_RANDOM_HPP
+#include "xbt/base.h"
+#include <random>
+
namespace simgrid {
namespace xbt {
namespace random {
+/** A random number generator.
+ *
+ * It uses a std::mersenne_twister_engine (std::mt19937) and provides several distributions.
+ * This interface is implemented by StdRandom and XbtRandom.
+ */
+class XBT_PUBLIC Random {
+public:
+ std::mt19937 mt19937_gen; // the random number engine
+
+ /** @brief Build a new random number generator with default seed */
+ Random() = default;
+ /** @brief Build a new random number generator with given seed */
+ Random(int seed) : mt19937_gen(seed) {}
+
+ virtual ~Random() = default;
+
+ /**
+ * @brief Sets the seed of the Mersenne-Twister RNG
+ */
+ void set_seed(int seed) { mt19937_gen.seed(seed); }
+
+ /**
+ * @brief Draws an integer number uniformly in range [min, max] (min and max included)
+ *
+ * @param min Minimum value
+ * @param max Maximum value
+ */
+ virtual int uniform_int(int min, int max) = 0;
+
+ /**
+ * @brief Draws a real number uniformly in range [min, max) (min included, and max excluded)
+ *
+ * @param min Minimum value
+ * @param max Maximum value
+ */
+ virtual double uniform_real(double min, double max) = 0;
+
+ /**
+ * @brief Draws a real number according to the given exponential distribution
+ *
+ * @param lambda Parameter of the exponential law
+ */
+ virtual double exponential(double lambda) = 0;
+
+ /**
+ * @brief Draws a real number according to the given normal distribution
+ *
+ * @param mean Mean of the normal distribution
+ * @param sd Standard deviation of the normal distribution
+ */
+ virtual double normal(double mean, double sd) = 0;
+};
+
+/** A random number generator using the C++ standard library.
+ *
+ * Caution: reproducibility is not guaranteed across different implementations.
+ */
+class XBT_PUBLIC StdRandom : public Random {
+public:
+ StdRandom() = default;
+ StdRandom(int seed) : Random(seed) {}
+
+ int uniform_int(int min, int max) override;
+ double uniform_real(double min, double max) override;
+ double exponential(double lambda) override;
+ double normal(double mean, double sd) override;
+};
+
+/** A reproducible random number generator.
+ *
+ * Uses our own implementation of distributions to ensure reproducibility.
+ */
+class XBT_PUBLIC XbtRandom : public Random {
+public:
+ XbtRandom() = default;
+ XbtRandom(int seed) : Random(seed) {}
+
+ int uniform_int(int min, int max) override;
+ double uniform_real(double min, double max) override;
+ double exponential(double lambda) override;
+ double normal(double mean, double sd) override;
+};
+
/**
* @brief Tells xbt/random to use the ad-hoc distribution implementation.
*/
