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_NEGATIVE_BINOMIAL_DISTRIBUTION_H
10 #define _LIBCPP___RANDOM_NEGATIVE_BINOMIAL_DISTRIBUTION_H
11
12 #include <__config>
13 #include <__random/bernoulli_distribution.h>
14 #include <__random/gamma_distribution.h>
15 #include <__random/is_valid.h>
16 #include <__random/poisson_distribution.h>
17 #include <iosfwd>
18 #include <limits>
19
20 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
21 # pragma GCC system_header
22 #endif
23
24 _LIBCPP_PUSH_MACROS
25 #include <__undef_macros>
26
27 _LIBCPP_BEGIN_NAMESPACE_STD
28
29 template <class _IntType = int>
30 class _LIBCPP_TEMPLATE_VIS negative_binomial_distribution {
31 static_assert(__libcpp_random_is_valid_inttype<_IntType>::value, "IntType must be a supported integer type");
32
33 public:
34 // types
35 typedef _IntType result_type;
36
37 class _LIBCPP_TEMPLATE_VIS param_type {
38 result_type __k_;
39 double __p_;
40
41 public:
42 typedef negative_binomial_distribution distribution_type;
43
__k_(__k)44 _LIBCPP_HIDE_FROM_ABI explicit param_type(result_type __k = 1, double __p = 0.5) : __k_(__k), __p_(__p) {}
45
k()46 _LIBCPP_HIDE_FROM_ABI result_type k() const { return __k_; }
p()47 _LIBCPP_HIDE_FROM_ABI double p() const { return __p_; }
48
49 friend _LIBCPP_HIDE_FROM_ABI bool operator==(const param_type& __x, const param_type& __y) {
50 return __x.__k_ == __y.__k_ && __x.__p_ == __y.__p_;
51 }
52 friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const param_type& __x, const param_type& __y) { return !(__x == __y); }
53 };
54
55 private:
56 param_type __p_;
57
58 public:
59 // constructor and reset functions
60 #ifndef _LIBCPP_CXX03_LANG
negative_binomial_distribution()61 _LIBCPP_HIDE_FROM_ABI negative_binomial_distribution() : negative_binomial_distribution(1) {}
__p_(__k,__p)62 _LIBCPP_HIDE_FROM_ABI explicit negative_binomial_distribution(result_type __k, double __p = 0.5) : __p_(__k, __p) {}
63 #else
64 _LIBCPP_HIDE_FROM_ABI explicit negative_binomial_distribution(result_type __k = 1, double __p = 0.5)
65 : __p_(__k, __p) {}
66 #endif
negative_binomial_distribution(const param_type & __p)67 _LIBCPP_HIDE_FROM_ABI explicit negative_binomial_distribution(const param_type& __p) : __p_(__p) {}
reset()68 _LIBCPP_HIDE_FROM_ABI void reset() {}
69
70 // generating functions
71 template <class _URNG>
operator()72 _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g) {
73 return (*this)(__g, __p_);
74 }
75 template <class _URNG>
76 _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
77
78 // property functions
k()79 _LIBCPP_HIDE_FROM_ABI result_type k() const { return __p_.k(); }
p()80 _LIBCPP_HIDE_FROM_ABI double p() const { return __p_.p(); }
81
param()82 _LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; }
param(const param_type & __p)83 _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; }
84
min()85 _LIBCPP_HIDE_FROM_ABI result_type min() const { return 0; }
max()86 _LIBCPP_HIDE_FROM_ABI result_type max() const { return numeric_limits<result_type>::max(); }
87
88 friend _LIBCPP_HIDE_FROM_ABI bool
89 operator==(const negative_binomial_distribution& __x, const negative_binomial_distribution& __y) {
90 return __x.__p_ == __y.__p_;
91 }
92 friend _LIBCPP_HIDE_FROM_ABI bool
93 operator!=(const negative_binomial_distribution& __x, const negative_binomial_distribution& __y) {
94 return !(__x == __y);
95 }
96 };
97
98 template <class _IntType>
99 template <class _URNG>
operator()100 _IntType negative_binomial_distribution<_IntType>::operator()(_URNG& __urng, const param_type& __pr) {
101 static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
102 result_type __k = __pr.k();
103 double __p = __pr.p();
104 // When the number of bits in _IntType is small, we are too likely to
105 // overflow __f below to use this technique.
106 if (__k <= 21 * __p && sizeof(_IntType) > 1) {
107 bernoulli_distribution __gen(__p);
108 result_type __f = 0;
109 result_type __s = 0;
110 while (__s < __k) {
111 if (__gen(__urng))
112 ++__s;
113 else
114 ++__f;
115 }
116 _LIBCPP_ASSERT_INTERNAL(__f >= 0,
117 "std::negative_binomial_distribution should never produce negative values. "
118 "This is almost certainly a signed integer overflow issue on __f.");
119 return __f;
120 }
121 return poisson_distribution<result_type>(gamma_distribution<double>(__k, (1 - __p) / __p)(__urng))(__urng);
122 }
123
124 template <class _CharT, class _Traits, class _IntType>
125 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
126 operator<<(basic_ostream<_CharT, _Traits>& __os, const negative_binomial_distribution<_IntType>& __x) {
127 __save_flags<_CharT, _Traits> __lx(__os);
128 typedef basic_ostream<_CharT, _Traits> _OStream;
129 __os.flags(_OStream::dec | _OStream::left | _OStream::fixed | _OStream::scientific);
130 _CharT __sp = __os.widen(' ');
131 __os.fill(__sp);
132 return __os << __x.k() << __sp << __x.p();
133 }
134
135 template <class _CharT, class _Traits, class _IntType>
136 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
137 operator>>(basic_istream<_CharT, _Traits>& __is, negative_binomial_distribution<_IntType>& __x) {
138 typedef negative_binomial_distribution<_IntType> _Eng;
139 typedef typename _Eng::result_type result_type;
140 typedef typename _Eng::param_type param_type;
141 __save_flags<_CharT, _Traits> __lx(__is);
142 typedef basic_istream<_CharT, _Traits> _Istream;
143 __is.flags(_Istream::dec | _Istream::skipws);
144 result_type __k;
145 double __p;
146 __is >> __k >> __p;
147 if (!__is.fail())
148 __x.param(param_type(__k, __p));
149 return __is;
150 }
151
152 _LIBCPP_END_NAMESPACE_STD
153
154 _LIBCPP_POP_MACROS
155
156 #endif // _LIBCPP___RANDOM_NEGATIVE_BINOMIAL_DISTRIBUTION_H
157