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 {
31 public:
32     // types
33     typedef _RealType result_type;
34 
35     class _LIBCPP_TEMPLATE_VIS param_type
36     {
37         result_type __mean_;
38         result_type __stddev_;
39     public:
40         typedef normal_distribution distribution_type;
41 
42         _LIBCPP_INLINE_VISIBILITY
43         explicit param_type(result_type __mean = 0, result_type __stddev = 1)
44             : __mean_(__mean), __stddev_(__stddev) {}
45 
46         _LIBCPP_INLINE_VISIBILITY
47         result_type mean() const {return __mean_;}
48         _LIBCPP_INLINE_VISIBILITY
49         result_type stddev() const {return __stddev_;}
50 
51         friend _LIBCPP_INLINE_VISIBILITY
52             bool operator==(const param_type& __x, const param_type& __y)
53             {return __x.__mean_ == __y.__mean_ && __x.__stddev_ == __y.__stddev_;}
54         friend _LIBCPP_INLINE_VISIBILITY
55             bool operator!=(const param_type& __x, const param_type& __y)
56             {return !(__x == __y);}
57     };
58 
59 private:
60     param_type __p_;
61     result_type __v_;
62     bool __v_hot_;
63 
64 public:
65     // constructors and reset functions
66 #ifndef _LIBCPP_CXX03_LANG
67     _LIBCPP_INLINE_VISIBILITY
68     normal_distribution() : normal_distribution(0) {}
69     _LIBCPP_INLINE_VISIBILITY
70     explicit normal_distribution(result_type __mean, result_type __stddev = 1)
71         : __p_(param_type(__mean, __stddev)), __v_hot_(false) {}
72 #else
73     _LIBCPP_INLINE_VISIBILITY
74     explicit normal_distribution(result_type __mean = 0,
75                                  result_type __stddev = 1)
76         : __p_(param_type(__mean, __stddev)), __v_hot_(false) {}
77 #endif
78     _LIBCPP_INLINE_VISIBILITY
79     explicit normal_distribution(const param_type& __p)
80         : __p_(__p), __v_hot_(false) {}
81     _LIBCPP_INLINE_VISIBILITY
82     void reset() {__v_hot_ = false;}
83 
84     // generating functions
85     template<class _URNG>
86         _LIBCPP_INLINE_VISIBILITY
87         result_type operator()(_URNG& __g)
88         {return (*this)(__g, __p_);}
89     template<class _URNG>
90     _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
91 
92     // property functions
93     _LIBCPP_INLINE_VISIBILITY
94     result_type mean() const {return __p_.mean();}
95     _LIBCPP_INLINE_VISIBILITY
96     result_type stddev() const {return __p_.stddev();}
97 
98     _LIBCPP_INLINE_VISIBILITY
99     param_type param() const {return __p_;}
100     _LIBCPP_INLINE_VISIBILITY
101     void param(const param_type& __p) {__p_ = __p;}
102 
103     _LIBCPP_INLINE_VISIBILITY
104     result_type min() const {return -numeric_limits<result_type>::infinity();}
105     _LIBCPP_INLINE_VISIBILITY
106     result_type max() const {return numeric_limits<result_type>::infinity();}
107 
108     friend _LIBCPP_INLINE_VISIBILITY
109         bool operator==(const normal_distribution& __x,
110                         const normal_distribution& __y)
111         {return __x.__p_ == __y.__p_ && __x.__v_hot_ == __y.__v_hot_ &&
112                 (!__x.__v_hot_ || __x.__v_ == __y.__v_);}
113     friend _LIBCPP_INLINE_VISIBILITY
114         bool operator!=(const normal_distribution& __x,
115                         const normal_distribution& __y)
116         {return !(__x == __y);}
117 
118     template <class _CharT, class _Traits, class _RT>
119     friend
120     basic_ostream<_CharT, _Traits>&
121     operator<<(basic_ostream<_CharT, _Traits>& __os,
122                const normal_distribution<_RT>& __x);
123 
124     template <class _CharT, class _Traits, class _RT>
125     friend
126     basic_istream<_CharT, _Traits>&
127     operator>>(basic_istream<_CharT, _Traits>& __is,
128                normal_distribution<_RT>& __x);
129 };
130 
131 template <class _RealType>
132 template<class _URNG>
133 _RealType
134 normal_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p)
135 {
136     static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
137     result_type __up;
138     if (__v_hot_)
139     {
140         __v_hot_ = false;
141         __up = __v_;
142     }
143     else
144     {
145         uniform_real_distribution<result_type> __uni(-1, 1);
146         result_type __u;
147         result_type __v;
148         result_type __s;
149         do
150         {
151             __u = __uni(__g);
152             __v = __uni(__g);
153             __s = __u * __u + __v * __v;
154         } while (__s > 1 || __s == 0);
155         result_type __fp = _VSTD::sqrt(-2 * _VSTD::log(__s) / __s);
156         __v_ = __v * __fp;
157         __v_hot_ = true;
158         __up = __u * __fp;
159     }
160     return __up * __p.stddev() + __p.mean();
161 }
162 
163 template <class _CharT, class _Traits, class _RT>
164 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
165 operator<<(basic_ostream<_CharT, _Traits>& __os,
166            const normal_distribution<_RT>& __x)
167 {
168     __save_flags<_CharT, _Traits> __lx(__os);
169     typedef basic_ostream<_CharT, _Traits> _OStream;
170     __os.flags(_OStream::dec | _OStream::left | _OStream::fixed |
171                _OStream::scientific);
172     _CharT __sp = __os.widen(' ');
173     __os.fill(__sp);
174     __os << __x.mean() << __sp << __x.stddev() << __sp << __x.__v_hot_;
175     if (__x.__v_hot_)
176         __os << __sp << __x.__v_;
177     return __os;
178 }
179 
180 template <class _CharT, class _Traits, class _RT>
181 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
182 operator>>(basic_istream<_CharT, _Traits>& __is,
183            normal_distribution<_RT>& __x)
184 {
185     typedef normal_distribution<_RT> _Eng;
186     typedef typename _Eng::result_type result_type;
187     typedef typename _Eng::param_type param_type;
188     __save_flags<_CharT, _Traits> __lx(__is);
189     typedef basic_istream<_CharT, _Traits> _Istream;
190     __is.flags(_Istream::dec | _Istream::skipws);
191     result_type __mean;
192     result_type __stddev;
193     result_type __vp = 0;
194     bool __v_hot = false;
195     __is >> __mean >> __stddev >> __v_hot;
196     if (__v_hot)
197         __is >> __vp;
198     if (!__is.fail())
199     {
200         __x.param(param_type(__mean, __stddev));
201         __x.__v_hot_ = __v_hot;
202         __x.__v_ = __vp;
203     }
204     return __is;
205 }
206 
207 _LIBCPP_END_NAMESPACE_STD
208 
209 _LIBCPP_POP_MACROS
210 
211 #endif // _LIBCPP___RANDOM_NORMAL_DISTRIBUTION_H
212