// SPDX-FileCopyrightText: Copyright (c) 2008-2013, NVIDIA Corporation. All rights reserved.
// SPDX-License-Identifier: Apache-2.0

/*! \file normal_distribution.h
 *  \brief A normal (Gaussian) distribution of real-valued numbers.
 */

#pragma once

#include <thrust/detail/config.h>

#if defined(_CCCL_IMPLICIT_SYSTEM_HEADER_GCC)
#  pragma GCC system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_CLANG)
#  pragma clang system_header
#elif defined(_CCCL_IMPLICIT_SYSTEM_HEADER_MSVC)
#  pragma system_header
#endif // no system header
#include <thrust/random/detail/normal_distribution_base.h>
#include <thrust/random/detail/random_core_access.h>

#include <cuda/std/__utility/pair.h>

#include <iostream>

THRUST_NAMESPACE_BEGIN

namespace random
{
/*! \addtogroup random_number_distributions
 *  \{
 */

/*! \class normal_distribution
 *  \brief A \p normal_distribution random number distribution produces floating point
 *         Normally distributed random numbers.
 *
 *  \tparam RealType The type of floating point number to produce.
 *
 *  The following code snippet demonstrates examples of using a \p normal_distribution with a
 *  random number engine to produce random values drawn from the Normal distribution with a given
 *  mean and variance:
 *
 *  \code
 *  #include <thrust/random/linear_congruential_engine.h>
 *  #include <thrust/random/normal_distribution.h>
 *
 *  int main()
 *  {
 *    // create a minstd_rand object to act as our source of randomness
 *    thrust::minstd_rand rng;
 *
 *    // create a normal_distribution to produce floats from the Normal distribution
 *    // with mean 2.0 and standard deviation 3.5
 *    thrust::random::normal_distribution<float> dist(2.0f, 3.5f);
 *
 *    // write a random number to standard output
 *    std::cout << dist(rng) << std::endl;
 *
 *    // write the mean of the distribution, just in case we forgot
 *    std::cout << dist.mean() << std::endl;
 *
 *    // 2.0 is printed
 *
 *    // and the standard deviation
 *    std::cout << dist.stddev() << std::endl;
 *
 *    // 3.5 is printed
 *
 *    return 0;
 *  }
 *  \endcode
 */
template <typename RealType = double>
class normal_distribution : public detail::normal_distribution_base<RealType>::type
{
private:
  using super_t = typename detail::normal_distribution_base<RealType>::type;

public:
  // types

  /*! \typedef result_type
   *  \brief The type of the floating point number produced by this \p normal_distribution.
   */
  using result_type = RealType;

  /*! \typedef param_type
   *  \brief The type of the object encapsulating this \p normal_distribution's parameters.
   */
  using param_type = ::cuda::std::pair<RealType, RealType>;

  // constructors and reset functions

  /*! This constructor creates a new \p normal_distribution from two values defining the
   *  half-open interval of the distribution.
   *
   *  \param mean The mean (expected value) of the distribution. Defaults to \c 0.0.
   *  \param stddev The standard deviation of the distribution. Defaults to \c 1.0.
   */
  _CCCL_HOST_DEVICE explicit normal_distribution(RealType mean = 0.0, RealType stddev = 1.0);

  /*! This constructor creates a new \p normal_distribution from a \p param_type object
   *  encapsulating the range of the distribution.
   *
   *  \param parm A \p param_type object encapsulating the parameters (i.e., the mean and standard deviation) of the
   * distribution.
   */
  _CCCL_HOST_DEVICE explicit normal_distribution(const param_type& parm);

  /*! Calling this member function guarantees that subsequent uses of this
   *  \p normal_distribution do not depend on values produced by any random
   *  number generator prior to invoking this function.
   */
  _CCCL_HOST_DEVICE void reset();

  // generating functions

  /*! This method produces a new Normal random integer drawn from this \p normal_distribution's
   *  range using a \p UniformRandomNumberGenerator as a source of randomness.
   *
   *  \param urng The \p UniformRandomNumberGenerator to use as a source of randomness.
   */
  template <typename UniformRandomNumberGenerator>
  _CCCL_HOST_DEVICE result_type operator()(UniformRandomNumberGenerator& urng);

  /*! This method produces a new Normal random integer as if by creating a new \p normal_distribution
   *  from the given \p param_type object, and calling its <tt>operator()</tt> method with the given
   *  \p UniformRandomNumberGenerator as a source of randomness.
   *
   *  \param urng The \p UniformRandomNumberGenerator to use as a source of randomness.
   *  \param parm A \p param_type object encapsulating the parameters of the \p normal_distribution
   *              to draw from.
   */
  template <typename UniformRandomNumberGenerator>
  _CCCL_HOST_DEVICE result_type operator()(UniformRandomNumberGenerator& urng, const param_type& parm);

  // property functions

  /*! This method returns the value of the parameter with which this \p normal_distribution
   *  was constructed.
   *
   *  \return The mean (expected value) of this \p normal_distribution's output.
   */
  _CCCL_HOST_DEVICE result_type mean() const;

  /*! This method returns the value of the parameter with which this \p normal_distribution
   *  was constructed.
   *
   *  \return The standard deviation of this \p uniform_real_distribution's output.
   */
  _CCCL_HOST_DEVICE result_type stddev() const;

  /*! This method returns a \p param_type object encapsulating the parameters with which this
   *  \p normal_distribution was constructed.
   *
   *  \return A \p param_type object encapsulating the parameters (i.e., the mean and standard deviation) of this \p
   * normal_distribution.
   */
  _CCCL_HOST_DEVICE param_type param() const;

  /*! This method changes the parameters of this \p normal_distribution using the values encapsulated
   *  in a given \p param_type object.
   *
   *  \param parm A \p param_type object encapsulating the new parameters (i.e., the mean and variance) of this \p
   * normal_distribution.
   */
  _CCCL_HOST_DEVICE void param(const param_type& parm);

  /*! This method returns the smallest floating point number this \p normal_distribution can potentially produce.
   *
   *  \return The lower bound of this \p normal_distribution's half-open interval.
   */
  _CCCL_HOST_DEVICE result_type min THRUST_PREVENT_MACRO_SUBSTITUTION() const;

  /*! This method returns the smallest number larger than largest floating point number this \p
   * uniform_real_distribution can potentially produce.
   *
   *  \return The upper bound of this \p normal_distribution's half-open interval.
   */
  _CCCL_HOST_DEVICE result_type max THRUST_PREVENT_MACRO_SUBSTITUTION() const;

  /*! \cond
   */

private:
  param_type m_param;

  friend struct thrust::random::detail::random_core_access;

  _CCCL_HOST_DEVICE bool equal(const normal_distribution& rhs) const;

  template <typename CharT, typename Traits>
  std::basic_ostream<CharT, Traits>& stream_out(std::basic_ostream<CharT, Traits>& os) const;

  template <typename CharT, typename Traits>
  std::basic_istream<CharT, Traits>& stream_in(std::basic_istream<CharT, Traits>& is);
  /*! \endcond
   */
}; // end normal_distribution

/*! This function checks two \p normal_distributions for equality.
 *  \param lhs The first \p normal_distribution to test.
 *  \param rhs The second \p normal_distribution to test.
 *  \return \c true if \p lhs is equal to \p rhs; \c false, otherwise.
 */
template <typename RealType>
_CCCL_HOST_DEVICE bool operator==(const normal_distribution<RealType>& lhs, const normal_distribution<RealType>& rhs);

/*! This function checks two \p normal_distributions for inequality.
 *  \param lhs The first \p normal_distribution to test.
 *  \param rhs The second \p normal_distribution to test.
 *  \return \c true if \p lhs is not equal to \p rhs; \c false, otherwise.
 */
template <typename RealType>
_CCCL_HOST_DEVICE bool operator!=(const normal_distribution<RealType>& lhs, const normal_distribution<RealType>& rhs);

/*! This function streams a normal_distribution to a \p std::basic_ostream.
 *  \param os The \p basic_ostream to stream out to.
 *  \param d The \p normal_distribution to stream out.
 *  \return \p os
 */
template <typename RealType, typename CharT, typename Traits>
std::basic_ostream<CharT, Traits>&
operator<<(std::basic_ostream<CharT, Traits>& os, const normal_distribution<RealType>& d);

/*! This function streams a normal_distribution in from a std::basic_istream.
 *  \param is The \p basic_istream to stream from.
 *  \param d The \p normal_distribution to stream in.
 *  \return \p is
 */
template <typename RealType, typename CharT, typename Traits>
std::basic_istream<CharT, Traits>& operator>>(std::basic_istream<CharT, Traits>& is, normal_distribution<RealType>& d);

/*! \} // end random_number_distributions
 */
} // namespace random

using random::normal_distribution;

THRUST_NAMESPACE_END

#include <thrust/random/detail/normal_distribution.inl>
