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