Class RandomSource

source/core/StarRandom.hpp:14–84

Deterministic random number source. Uses multiply-with-carry algorithm. Much higher quality than the predictable random number generators. Not thread safe (won't crash or anything, but might return less than optimal values).

// thread safe (won't crash or anything, but might return less than optimal
// values).
class RandomSource {
public:
  // Generates a RandomSource with a seed from Random::randu64()
  RandomSource();
  RandomSource(uint64_t seed);

  // Re-initializes the random number generator using the given seed.  It is
  // exactly equivalent to constructing a new RandomSource, just using the same
  // buffer.
  void init();
  void init(uint64_t seed);

  void addEntropy();
  void addEntropy(uint64_t seed);

  uint32_t randu32();
  uint64_t randu64();

  int32_t randi32();
  int64_t randi64();

  // Generates values in the range [0.0, 1.0]
  float randf();
  // Generates values in the range [0.0, 1.0]
  double randd();

  // Random integer from [0, max], max must be >= 0
  int64_t randInt(int64_t max);
  uint64_t randUInt(uint64_t max);

  // Random integer from [min, max]
  int64_t randInt(int64_t min, int64_t max);
  uint64_t randUInt(uint64_t min, uint64_t max);

  float randf(float min, float max);
  double randd(double min, double max);

  bool randb();

  // Generates values via normal distribution with box-muller algorithm
  float nrandf(float stddev = 1.0f, float mean = 0.0f);
  double nrandd(double stddev = 1.0, double mean = 0.0);

  // Round a fractional value statistically towards the floor or ceiling.  For
  // example, if a value is 5.2, 80% of the time it will round to 5, but 20% of
  // the time it will round to 6.
  int64_t stochasticRound(double val);

  void randBytes(char* buf, size_t len);
  ByteArray randBytes(size_t len);

  // Pick a random value out of a container
  template <typename Container>
  typename Container::value_type const& randFrom(Container const& container);
  template <typename Container>
  typename Container::value_type& randFrom(Container& container);
  template <typename Container>
  typename Container::value_type randValueFrom(Container const& container);