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___CXX03___RANDOM_NEGATIVE_BINOMIAL_DISTRIBUTION_H
10 #define _LIBCPP___CXX03___RANDOM_NEGATIVE_BINOMIAL_DISTRIBUTION_H
11
12 #include <__cxx03/__assert>
13 #include <__cxx03/__config>
14 #include <__cxx03/__random/bernoulli_distribution.h>
15 #include <__cxx03/__random/gamma_distribution.h>
16 #include <__cxx03/__random/is_valid.h>
17 #include <__cxx03/__random/poisson_distribution.h>
18 #include <__cxx03/iosfwd>
19 #include <__cxx03/limits>
20
21 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
22 # pragma GCC system_header
23 #endif
24
25 _LIBCPP_PUSH_MACROS
26 #include <__cxx03/__undef_macros>
27
28 _LIBCPP_BEGIN_NAMESPACE_STD
29
30 template <class _IntType = int>
31 class _LIBCPP_TEMPLATE_VIS negative_binomial_distribution {
32 static_assert(__libcpp_random_is_valid_inttype<_IntType>::value, "IntType must be a supported integer type");
33
34 public:
35 // types
36 typedef _IntType result_type;
37
38 class _LIBCPP_TEMPLATE_VIS param_type {
39 result_type __k_;
40 double __p_;
41
42 public:
43 typedef negative_binomial_distribution distribution_type;
44
__k_(__k)45 _LIBCPP_HIDE_FROM_ABI explicit param_type(result_type __k = 1, double __p = 0.5) : __k_(__k), __p_(__p) {}
46
k()47 _LIBCPP_HIDE_FROM_ABI result_type k() const { return __k_; }
p()48 _LIBCPP_HIDE_FROM_ABI double p() const { return __p_; }
49
50 friend _LIBCPP_HIDE_FROM_ABI bool operator==(const param_type& __x, const param_type& __y) {
51 return __x.__k_ == __y.__k_ && __x.__p_ == __y.__p_;
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
59 public:
60 // constructor and reset functions
61 _LIBCPP_HIDE_FROM_ABI explicit negative_binomial_distribution(result_type __k = 1, double __p = 0.5)
__p_(__k,__p)62 : __p_(__k, __p) {}
negative_binomial_distribution(const param_type & __p)63 _LIBCPP_HIDE_FROM_ABI explicit negative_binomial_distribution(const param_type& __p) : __p_(__p) {}
reset()64 _LIBCPP_HIDE_FROM_ABI void reset() {}
65
66 // generating functions
67 template <class _URNG>
operator()68 _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g) {
69 return (*this)(__g, __p_);
70 }
71 template <class _URNG>
72 _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
73
74 // property functions
k()75 _LIBCPP_HIDE_FROM_ABI result_type k() const { return __p_.k(); }
p()76 _LIBCPP_HIDE_FROM_ABI double p() const { return __p_.p(); }
77
param()78 _LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; }
param(const param_type & __p)79 _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; }
80
min()81 _LIBCPP_HIDE_FROM_ABI result_type min() const { return 0; }
max()82 _LIBCPP_HIDE_FROM_ABI result_type max() const { return numeric_limits<result_type>::max(); }
83
84 friend _LIBCPP_HIDE_FROM_ABI bool
85 operator==(const negative_binomial_distribution& __x, const negative_binomial_distribution& __y) {
86 return __x.__p_ == __y.__p_;
87 }
88 friend _LIBCPP_HIDE_FROM_ABI bool
89 operator!=(const negative_binomial_distribution& __x, const negative_binomial_distribution& __y) {
90 return !(__x == __y);
91 }
92 };
93
94 template <class _IntType>
95 template <class _URNG>
operator()96 _IntType negative_binomial_distribution<_IntType>::operator()(_URNG& __urng, const param_type& __pr) {
97 static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
98 result_type __k = __pr.k();
99 double __p = __pr.p();
100 // When the number of bits in _IntType is small, we are too likely to
101 // overflow __f below to use this technique.
102 if (__k <= 21 * __p && sizeof(_IntType) > 1) {
103 bernoulli_distribution __gen(__p);
104 result_type __f = 0;
105 result_type __s = 0;
106 while (__s < __k) {
107 if (__gen(__urng))
108 ++__s;
109 else
110 ++__f;
111 }
112 _LIBCPP_ASSERT_INTERNAL(__f >= 0,
113 "std::negative_binomial_distribution should never produce negative values. "
114 "This is almost certainly a signed integer overflow issue on __f.");
115 return __f;
116 }
117 return poisson_distribution<result_type>(gamma_distribution<double>(__k, (1 - __p) / __p)(__urng))(__urng);
118 }
119
120 template <class _CharT, class _Traits, class _IntType>
121 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
122 operator<<(basic_ostream<_CharT, _Traits>& __os, const negative_binomial_distribution<_IntType>& __x) {
123 __save_flags<_CharT, _Traits> __lx(__os);
124 typedef basic_ostream<_CharT, _Traits> _OStream;
125 __os.flags(_OStream::dec | _OStream::left | _OStream::fixed | _OStream::scientific);
126 _CharT __sp = __os.widen(' ');
127 __os.fill(__sp);
128 return __os << __x.k() << __sp << __x.p();
129 }
130
131 template <class _CharT, class _Traits, class _IntType>
132 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
133 operator>>(basic_istream<_CharT, _Traits>& __is, negative_binomial_distribution<_IntType>& __x) {
134 typedef negative_binomial_distribution<_IntType> _Eng;
135 typedef typename _Eng::result_type result_type;
136 typedef typename _Eng::param_type param_type;
137 __save_flags<_CharT, _Traits> __lx(__is);
138 typedef basic_istream<_CharT, _Traits> _Istream;
139 __is.flags(_Istream::dec | _Istream::skipws);
140 result_type __k;
141 double __p;
142 __is >> __k >> __p;
143 if (!__is.fail())
144 __x.param(param_type(__k, __p));
145 return __is;
146 }
147
148 _LIBCPP_END_NAMESPACE_STD
149
150 _LIBCPP_POP_MACROS
151
152 #endif // _LIBCPP___CXX03___RANDOM_NEGATIVE_BINOMIAL_DISTRIBUTION_H
153