Random.h

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#ifndef OPENANN_UTIL_RANDOM_H_
#define OPENANN_UTIL_RANDOM_H_

#include <OpenANN/util/AssertionMacros.h>
#include <cmath>
#include <cstdlib>
#include <algorithm>

namespace OpenANN
{

class RandomNumberGenerator
{
public:
  RandomNumberGenerator();
  void seed(unsigned int seed);
  int generateInt(int min, int range) const;
  size_t generateIndex(size_t size) const;

  template<class T>
  T generate(T min, T range) const
  {
    OPENANN_CHECK(range >= T());
    if(range == T())
      return min;
    else
      return (T) rand() / (T) RAND_MAX * range + min;
  }

  template<class T>
  T sampleNormalDistribution() const
  {
    return std::sqrt(T(-2) * std::log(generate(T(), T(1)))) *
           std::cos(T(2) * T(M_PI) * generate(T(), T(1)));
  }

  template<class C>
  void generateIndices(int n, C& result, bool initialized = false)
  {
    if(!initialized)
    {
      OPENANN_CHECK_EQUALS(result.size(), 0);
      for(int i = 0; i < n; i++)
        result.push_back(i);
    }
    else
    {
      OPENANN_CHECK_EQUALS(result.size(), (size_t) n);
    }
    std::random_shuffle(result.begin(), result.end());
  }

  template<class M>
  void fillNormalDistribution(M& matrix, double stdDev = 1.0)
  {
    const double* end = matrix.data() + matrix.rows() * matrix.cols();
    for(double* p = matrix.data(); p < end; p++)
        *p = sampleNormalDistribution<double>() * stdDev;
  }
};

} // namespace OpenANN

#endif // OPENANN_UTIL_RANDOM_H_