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_BINOMIAL_DISTRIBUTION_H
10 #define _LIBCPP___RANDOM_BINOMIAL_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
18 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
19 # pragma GCC system_header
20 #endif
21
22 _LIBCPP_PUSH_MACROS
23 #include <__undef_macros>
24
25 _LIBCPP_BEGIN_NAMESPACE_STD
26
27 template<class _IntType = int>
28 class _LIBCPP_TEMPLATE_VIS binomial_distribution
29 {
30 static_assert(__libcpp_random_is_valid_inttype<_IntType>::value, "IntType must be a supported integer type");
31 public:
32 // types
33 typedef _IntType result_type;
34
35 class _LIBCPP_TEMPLATE_VIS param_type
36 {
37 result_type __t_;
38 double __p_;
39 double __pr_;
40 double __odds_ratio_;
41 result_type __r0_;
42 public:
43 typedef binomial_distribution distribution_type;
44
45 explicit param_type(result_type __t = 1, double __p = 0.5);
46
47 _LIBCPP_INLINE_VISIBILITY
t()48 result_type t() const {return __t_;}
49 _LIBCPP_INLINE_VISIBILITY
p()50 double p() const {return __p_;}
51
52 friend _LIBCPP_INLINE_VISIBILITY
53 bool operator==(const param_type& __x, const param_type& __y)
54 {return __x.__t_ == __y.__t_ && __x.__p_ == __y.__p_;}
55 friend _LIBCPP_INLINE_VISIBILITY
56 bool operator!=(const param_type& __x, const param_type& __y)
57 {return !(__x == __y);}
58
59 friend class binomial_distribution;
60 };
61
62 private:
63 param_type __p_;
64
65 public:
66 // constructors and reset functions
67 #ifndef _LIBCPP_CXX03_LANG
68 _LIBCPP_INLINE_VISIBILITY
binomial_distribution()69 binomial_distribution() : binomial_distribution(1) {}
70 _LIBCPP_INLINE_VISIBILITY
71 explicit binomial_distribution(result_type __t, double __p = 0.5)
__p_(param_type (__t,__p))72 : __p_(param_type(__t, __p)) {}
73 #else
74 _LIBCPP_INLINE_VISIBILITY
75 explicit binomial_distribution(result_type __t = 1, double __p = 0.5)
76 : __p_(param_type(__t, __p)) {}
77 #endif
78 _LIBCPP_INLINE_VISIBILITY
binomial_distribution(const param_type & __p)79 explicit binomial_distribution(const param_type& __p) : __p_(__p) {}
80 _LIBCPP_INLINE_VISIBILITY
reset()81 void reset() {}
82
83 // generating functions
84 template<class _URNG>
85 _LIBCPP_INLINE_VISIBILITY
operator()86 result_type operator()(_URNG& __g)
87 {return (*this)(__g, __p_);}
88 template<class _URNG> result_type operator()(_URNG& __g, const param_type& __p);
89
90 // property functions
91 _LIBCPP_INLINE_VISIBILITY
t()92 result_type t() const {return __p_.t();}
93 _LIBCPP_INLINE_VISIBILITY
p()94 double p() const {return __p_.p();}
95
96 _LIBCPP_INLINE_VISIBILITY
param()97 param_type param() const {return __p_;}
98 _LIBCPP_INLINE_VISIBILITY
param(const param_type & __p)99 void param(const param_type& __p) {__p_ = __p;}
100
101 _LIBCPP_INLINE_VISIBILITY
min()102 result_type min() const {return 0;}
103 _LIBCPP_INLINE_VISIBILITY
max()104 result_type max() const {return t();}
105
106 friend _LIBCPP_INLINE_VISIBILITY
107 bool operator==(const binomial_distribution& __x,
108 const binomial_distribution& __y)
109 {return __x.__p_ == __y.__p_;}
110 friend _LIBCPP_INLINE_VISIBILITY
111 bool operator!=(const binomial_distribution& __x,
112 const binomial_distribution& __y)
113 {return !(__x == __y);}
114 };
115
116 #ifndef _LIBCPP_MSVCRT_LIKE
117 extern "C" double lgamma_r(double, int *);
118 #endif
119
__libcpp_lgamma(double __d)120 inline _LIBCPP_INLINE_VISIBILITY double __libcpp_lgamma(double __d) {
121 #if defined(_LIBCPP_MSVCRT_LIKE)
122 return lgamma(__d);
123 #else
124 int __sign;
125 return lgamma_r(__d, &__sign);
126 #endif
127 }
128
129 template<class _IntType>
param_type(result_type __t,double __p)130 binomial_distribution<_IntType>::param_type::param_type(result_type __t, double __p)
131 : __t_(__t), __p_(__p)
132 {
133 if (0 < __p_ && __p_ < 1)
134 {
135 __r0_ = static_cast<result_type>((__t_ + 1) * __p_);
136 __pr_ = _VSTD::exp(std::__libcpp_lgamma(__t_ + 1.) -
137 std::__libcpp_lgamma(__r0_ + 1.) -
138 std::__libcpp_lgamma(__t_ - __r0_ + 1.) + __r0_ * _VSTD::log(__p_) +
139 (__t_ - __r0_) * _VSTD::log(1 - __p_));
140 __odds_ratio_ = __p_ / (1 - __p_);
141 }
142 }
143
144 // Reference: Kemp, C.D. (1986). `A modal method for generating binomial
145 // variables', Commun. Statist. - Theor. Meth. 15(3), 805-813.
146 template<class _IntType>
147 template<class _URNG>
148 _IntType
operator()149 binomial_distribution<_IntType>::operator()(_URNG& __g, const param_type& __pr)
150 {
151 static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
152 if (__pr.__t_ == 0 || __pr.__p_ == 0)
153 return 0;
154 if (__pr.__p_ == 1)
155 return __pr.__t_;
156 uniform_real_distribution<double> __gen;
157 double __u = __gen(__g) - __pr.__pr_;
158 if (__u < 0)
159 return __pr.__r0_;
160 double __pu = __pr.__pr_;
161 double __pd = __pu;
162 result_type __ru = __pr.__r0_;
163 result_type __rd = __ru;
164 while (true)
165 {
166 bool __break = true;
167 if (__rd >= 1)
168 {
169 __pd *= __rd / (__pr.__odds_ratio_ * (__pr.__t_ - __rd + 1));
170 __u -= __pd;
171 __break = false;
172 if (__u < 0)
173 return __rd - 1;
174 }
175 if ( __rd != 0 )
176 --__rd;
177 ++__ru;
178 if (__ru <= __pr.__t_)
179 {
180 __pu *= (__pr.__t_ - __ru + 1) * __pr.__odds_ratio_ / __ru;
181 __u -= __pu;
182 __break = false;
183 if (__u < 0)
184 return __ru;
185 }
186 if (__break)
187 return 0;
188 }
189 }
190
191 template <class _CharT, class _Traits, class _IntType>
192 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
193 operator<<(basic_ostream<_CharT, _Traits>& __os,
194 const binomial_distribution<_IntType>& __x)
195 {
196 __save_flags<_CharT, _Traits> __lx(__os);
197 typedef basic_ostream<_CharT, _Traits> _OStream;
198 __os.flags(_OStream::dec | _OStream::left | _OStream::fixed |
199 _OStream::scientific);
200 _CharT __sp = __os.widen(' ');
201 __os.fill(__sp);
202 return __os << __x.t() << __sp << __x.p();
203 }
204
205 template <class _CharT, class _Traits, class _IntType>
206 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
207 operator>>(basic_istream<_CharT, _Traits>& __is,
208 binomial_distribution<_IntType>& __x)
209 {
210 typedef binomial_distribution<_IntType> _Eng;
211 typedef typename _Eng::result_type result_type;
212 typedef typename _Eng::param_type param_type;
213 __save_flags<_CharT, _Traits> __lx(__is);
214 typedef basic_istream<_CharT, _Traits> _Istream;
215 __is.flags(_Istream::dec | _Istream::skipws);
216 result_type __t;
217 double __p;
218 __is >> __t >> __p;
219 if (!__is.fail())
220 __x.param(param_type(__t, __p));
221 return __is;
222 }
223
224 _LIBCPP_END_NAMESPACE_STD
225
226 _LIBCPP_POP_MACROS
227
228 #endif // _LIBCPP___RANDOM_BINOMIAL_DISTRIBUTION_H
229