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//-----------------------------------------------------------------------------
/** @file libboardgame_base/RandomGenerator.h
@author Markus Enzenberger
@copyright GNU General Public License version 3 or later */
//-----------------------------------------------------------------------------
#ifndef LIBBOARDGAME_BASE_RANDOM_GENERATOR_H
#define LIBBOARDGAME_BASE_RANDOM_GENERATOR_H
#include <random>
namespace libboardgame_base {
using namespace std;
//-----------------------------------------------------------------------------
/** Fast pseudo-random number generator.
This is a fast and low-quality pseudo-random number generator for tasks
like opening book move selection or even playouts in Monte-Carlo tree
search (does not seem to be sensitive to the quality of the generator).
All instances of this class register themselves automatically at a
global list of random generators, such that the random seed can be
changed at all existing generators with a single function call.
Thread-safe after construction. */
class RandomGenerator
{
public:
using Generator = minstd_rand;
using ResultType = Generator::result_type;
/** Set seed for all currently existing and future generators.
If this function is never called, a non-deterministic seed is used. */
static void set_global_seed(ResultType seed);
/** Set seed to last seed for all currently existing and future
generators.
Sets the seed to the last seed that was set with set_seed(). If no seed
was explicitly defined with set_seed(), then this function does
nothing. */
static void set_global_seed_last();
/** Check if a global seed was set.
User code might want to take more measures if a global seed was set to
become fully deterministic (e.g. avoid decisions based on time
measurements). */
static bool has_global_seed();
/** Constructor.
Constructs the random generator with the global seed, if one was
defined, otherwise with a non-deterministic seed. */
RandomGenerator();
~RandomGenerator();
RandomGenerator(const RandomGenerator&) = delete;
RandomGenerator& operator=(const RandomGenerator&) = delete;
void set_seed(ResultType seed) { m_generator.seed(seed); }
ResultType generate() { return m_generator(); }
/** Generate a float in [a..b]. */
float generate_float(float a, float b);
private:
Generator m_generator;
};
inline float RandomGenerator::generate_float(float a, float b)
{
uniform_real_distribution<float> distribution(a, b);
return distribution(m_generator);
}
//-----------------------------------------------------------------------------
} // namespace libboardgame_base
#endif // LIBBOARDGAME_BASE_RANDOM_GENERATOR_H
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