libcxx/include/__random/normal_distribution.h

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef _LIBCPP___RANDOM_NORMAL_DISTRIBUTION_H
  10 #define _LIBCPP___RANDOM_NORMAL_DISTRIBUTION_H
  11
  12 #include <__config>
  13 #include <__random/is_valid.h>
  14 #include <__random/uniform_real_distribution.h>
  15 #include <cmath>
  16 #include <iosfwd>
  17 #include <limits>
  18
  19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  20 #  pragma GCC system_header
  21 #endif
  22
  23 _LIBCPP_PUSH_MACROS
  24 #include <__undef_macros>
  25
  26 _LIBCPP_BEGIN_NAMESPACE_STD
  27
  28 template <class _RealType = double>
  29 class _LIBCPP_TEMPLATE_VIS normal_distribution {
  30   static_assert(__libcpp_random_is_valid_realtype<_RealType>::value,
  31                 "RealType must be a supported floating-point type");
  32
  33 public:
  34   // types
  35   typedef _RealType result_type;
  36
  37   class _LIBCPP_TEMPLATE_VIS param_type {
  38     result_type __mean_;
  39     result_type __stddev_;
  40
  41   public:
  42     typedef normal_distribution distribution_type;
  43
  44     _LIBCPP_HIDE_FROM_ABI explicit param_type(result_type __mean = 0, result_type __stddev = 1)
  45         : __mean_(__mean), __stddev_(__stddev) {}
  46
  47     _LIBCPP_HIDE_FROM_ABI result_type mean() const { return __mean_; }
  48     _LIBCPP_HIDE_FROM_ABI result_type stddev() const { return __stddev_; }
  49
  50     friend _LIBCPP_HIDE_FROM_ABI bool operator==(const param_type& __x, const param_type& __y) {
  51       return __x.__mean_ == __y.__mean_ && __x.__stddev_ == __y.__stddev_;
  52     }
  53     friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const param_type& __x, const param_type& __y) { return !(__x == __y); }
  54   };
  55
  56 private:
  57   param_type __p_;
  58   result_type __v_;
  59   bool __v_hot_;
  60
  61 public:
  62   // constructors and reset functions
  63 #ifndef _LIBCPP_CXX03_LANG
  64   _LIBCPP_HIDE_FROM_ABI normal_distribution() : normal_distribution(0) {}
  65   _LIBCPP_HIDE_FROM_ABI explicit normal_distribution(result_type __mean, result_type __stddev = 1)
  66       : __p_(param_type(__mean, __stddev)), __v_hot_(false) {}
  67 #else
  68   _LIBCPP_HIDE_FROM_ABI explicit normal_distribution(result_type __mean = 0, result_type __stddev = 1)
  69       : __p_(param_type(__mean, __stddev)), __v_hot_(false) {}
  70 #endif
  71   _LIBCPP_HIDE_FROM_ABI explicit normal_distribution(const param_type& __p) : __p_(__p), __v_hot_(false) {}
  72   _LIBCPP_HIDE_FROM_ABI void reset() { __v_hot_ = false; }
  73
  74   // generating functions
  75   template <class _URNG>
  76   _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g) {
  77     return (*this)(__g, __p_);
  78   }
  79   template <class _URNG>
  80   _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
  81
  82   // property functions
  83   _LIBCPP_HIDE_FROM_ABI result_type mean() const { return __p_.mean(); }
  84   _LIBCPP_HIDE_FROM_ABI result_type stddev() const { return __p_.stddev(); }
  85
  86   _LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; }
  87   _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; }
  88
  89   _LIBCPP_HIDE_FROM_ABI result_type min() const { return -numeric_limits<result_type>::infinity(); }
  90   _LIBCPP_HIDE_FROM_ABI result_type max() const { return numeric_limits<result_type>::infinity(); }
  91
  92   friend _LIBCPP_HIDE_FROM_ABI bool operator==(const normal_distribution& __x, const normal_distribution& __y) {
  93     return __x.__p_ == __y.__p_ && __x.__v_hot_ == __y.__v_hot_ && (!__x.__v_hot_ || __x.__v_ == __y.__v_);
  94   }
  95   friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const normal_distribution& __x, const normal_distribution& __y) {
  96     return !(__x == __y);
  97   }
  98
  99   template <class _CharT, class _Traits, class _RT>
 100   friend basic_ostream<_CharT, _Traits>&
 101   operator<<(basic_ostream<_CharT, _Traits>& __os, const normal_distribution<_RT>& __x);
 102
 103   template <class _CharT, class _Traits, class _RT>
 104   friend basic_istream<_CharT, _Traits>&
 105   operator>>(basic_istream<_CharT, _Traits>& __is, normal_distribution<_RT>& __x);
 106 };
 107
 108 template <class _RealType>
 109 template <class _URNG>
 110 _RealType normal_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p) {
 111   static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
 112   result_type __up;
 113   if (__v_hot_) {
 114     __v_hot_ = false;
 115     __up     = __v_;
 116   } else {
 117     uniform_real_distribution<result_type> __uni(-1, 1);
 118     result_type __u;
 119     result_type __v;
 120     result_type __s;
 121     do {
 122       __u = __uni(__g);
 123       __v = __uni(__g);
 124       __s = __u * __u + __v * __v;
 125     } while (__s > 1 || __s == 0);
 126     result_type __fp = std::sqrt(-2 * std::log(__s) / __s);
 127     __v_             = __v * __fp;
 128     __v_hot_         = true;
 129     __up             = __u * __fp;
 130   }
 131   return __up * __p.stddev() + __p.mean();
 132 }
 133
 134 template <class _CharT, class _Traits, class _RT>
 135 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
 136 operator<<(basic_ostream<_CharT, _Traits>& __os, const normal_distribution<_RT>& __x) {
 137   __save_flags<_CharT, _Traits> __lx(__os);
 138   typedef basic_ostream<_CharT, _Traits> _OStream;
 139   __os.flags(_OStream::dec | _OStream::left | _OStream::fixed | _OStream::scientific);
 140   _CharT __sp = __os.widen(' ');
 141   __os.fill(__sp);
 142   __os << __x.mean() << __sp << __x.stddev() << __sp << __x.__v_hot_;
 143   if (__x.__v_hot_)
 144     __os << __sp << __x.__v_;
 145   return __os;
 146 }
 147
 148 template <class _CharT, class _Traits, class _RT>
 149 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
 150 operator>>(basic_istream<_CharT, _Traits>& __is, normal_distribution<_RT>& __x) {
 151   typedef normal_distribution<_RT> _Eng;
 152   typedef typename _Eng::result_type result_type;
 153   typedef typename _Eng::param_type param_type;
 154   __save_flags<_CharT, _Traits> __lx(__is);
 155   typedef basic_istream<_CharT, _Traits> _Istream;
 156   __is.flags(_Istream::dec | _Istream::skipws);
 157   result_type __mean;
 158   result_type __stddev;
 159   result_type __vp = 0;
 160   bool __v_hot     = false;
 161   __is >> __mean >> __stddev >> __v_hot;
 162   if (__v_hot)
 163     __is >> __vp;
 164   if (!__is.fail()) {
 165     __x.param(param_type(__mean, __stddev));
 166     __x.__v_hot_ = __v_hot;
 167     __x.__v_     = __vp;
 168   }
 169   return __is;
 170 }
 171
 172 _LIBCPP_END_NAMESPACE_STD
 173
 174 _LIBCPP_POP_MACROS
 175
 176 #endif // _LIBCPP___RANDOM_NORMAL_DISTRIBUTION_H