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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-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef _LIBCPP___CXX03___RANDOM_BINOMIAL_DISTRIBUTION_H10#define _LIBCPP___CXX03___RANDOM_BINOMIAL_DISTRIBUTION_H11 12#include <__cxx03/__config>13#include <__cxx03/__random/is_valid.h>14#include <__cxx03/__random/uniform_real_distribution.h>15#include <__cxx03/cmath>16#include <__cxx03/iosfwd>17 18#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)19# pragma GCC system_header20#endif21 22_LIBCPP_PUSH_MACROS23#include <__cxx03/__undef_macros>24 25_LIBCPP_BEGIN_NAMESPACE_STD26 27template <class _IntType = int>28class _LIBCPP_TEMPLATE_VIS binomial_distribution {29 static_assert(__libcpp_random_is_valid_inttype<_IntType>::value, "IntType must be a supported integer type");30 31public:32 // types33 typedef _IntType result_type;34 35 class _LIBCPP_TEMPLATE_VIS param_type {36 result_type __t_;37 double __p_;38 double __pr_;39 double __odds_ratio_;40 result_type __r0_;41 42 public:43 typedef binomial_distribution distribution_type;44 45 _LIBCPP_HIDE_FROM_ABI explicit param_type(result_type __t = 1, double __p = 0.5);46 47 _LIBCPP_HIDE_FROM_ABI result_type t() const { return __t_; }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.__t_ == __y.__t_ && __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 friend class binomial_distribution;56 };57 58private:59 param_type __p_;60 61public:62 // constructors and reset functions63 _LIBCPP_HIDE_FROM_ABI explicit binomial_distribution(result_type __t = 1, double __p = 0.5)64 : __p_(param_type(__t, __p)) {}65 _LIBCPP_HIDE_FROM_ABI explicit binomial_distribution(const param_type& __p) : __p_(__p) {}66 _LIBCPP_HIDE_FROM_ABI void reset() {}67 68 // generating functions69 template <class _URNG>70 _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g) {71 return (*this)(__g, __p_);72 }73 template <class _URNG>74 _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);75 76 // property functions77 _LIBCPP_HIDE_FROM_ABI result_type t() const { return __p_.t(); }78 _LIBCPP_HIDE_FROM_ABI double p() const { return __p_.p(); }79 80 _LIBCPP_HIDE_FROM_ABI param_type param() const { return __p_; }81 _LIBCPP_HIDE_FROM_ABI void param(const param_type& __p) { __p_ = __p; }82 83 _LIBCPP_HIDE_FROM_ABI result_type min() const { return 0; }84 _LIBCPP_HIDE_FROM_ABI result_type max() const { return t(); }85 86 friend _LIBCPP_HIDE_FROM_ABI bool operator==(const binomial_distribution& __x, const binomial_distribution& __y) {87 return __x.__p_ == __y.__p_;88 }89 friend _LIBCPP_HIDE_FROM_ABI bool operator!=(const binomial_distribution& __x, const binomial_distribution& __y) {90 return !(__x == __y);91 }92};93 94#ifndef _LIBCPP_MSVCRT_LIKE95extern "C" double lgamma_r(double, int*);96#endif97 98inline _LIBCPP_HIDE_FROM_ABI double __libcpp_lgamma(double __d) {99#if defined(_LIBCPP_MSVCRT_LIKE)100 return lgamma(__d);101#else102 int __sign;103 return lgamma_r(__d, &__sign);104#endif105}106 107template <class _IntType>108binomial_distribution<_IntType>::param_type::param_type(result_type __t, double __p) : __t_(__t), __p_(__p) {109 if (0 < __p_ && __p_ < 1) {110 __r0_ = static_cast<result_type>((__t_ + 1) * __p_);111 __pr_ = std::exp(112 std::__libcpp_lgamma(__t_ + 1.) - std::__libcpp_lgamma(__r0_ + 1.) - std::__libcpp_lgamma(__t_ - __r0_ + 1.) +113 __r0_ * std::log(__p_) + (__t_ - __r0_) * std::log(1 - __p_));114 __odds_ratio_ = __p_ / (1 - __p_);115 }116}117 118// Reference: Kemp, C.D. (1986). `A modal method for generating binomial119// variables', Commun. Statist. - Theor. Meth. 15(3), 805-813.120template <class _IntType>121template <class _URNG>122_IntType binomial_distribution<_IntType>::operator()(_URNG& __g, const param_type& __pr) {123 static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");124 if (__pr.__t_ == 0 || __pr.__p_ == 0)125 return 0;126 if (__pr.__p_ == 1)127 return __pr.__t_;128 uniform_real_distribution<double> __gen;129 double __u = __gen(__g) - __pr.__pr_;130 if (__u < 0)131 return __pr.__r0_;132 double __pu = __pr.__pr_;133 double __pd = __pu;134 result_type __ru = __pr.__r0_;135 result_type __rd = __ru;136 while (true) {137 bool __break = true;138 if (__rd >= 1) {139 __pd *= __rd / (__pr.__odds_ratio_ * (__pr.__t_ - __rd + 1));140 __u -= __pd;141 __break = false;142 if (__u < 0)143 return __rd - 1;144 }145 if (__rd != 0)146 --__rd;147 ++__ru;148 if (__ru <= __pr.__t_) {149 __pu *= (__pr.__t_ - __ru + 1) * __pr.__odds_ratio_ / __ru;150 __u -= __pu;151 __break = false;152 if (__u < 0)153 return __ru;154 }155 if (__break)156 return 0;157 }158}159 160template <class _CharT, class _Traits, class _IntType>161_LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&162operator<<(basic_ostream<_CharT, _Traits>& __os, const binomial_distribution<_IntType>& __x) {163 __save_flags<_CharT, _Traits> __lx(__os);164 typedef basic_ostream<_CharT, _Traits> _OStream;165 __os.flags(_OStream::dec | _OStream::left | _OStream::fixed | _OStream::scientific);166 _CharT __sp = __os.widen(' ');167 __os.fill(__sp);168 return __os << __x.t() << __sp << __x.p();169}170 171template <class _CharT, class _Traits, class _IntType>172_LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&173operator>>(basic_istream<_CharT, _Traits>& __is, binomial_distribution<_IntType>& __x) {174 typedef binomial_distribution<_IntType> _Eng;175 typedef typename _Eng::result_type result_type;176 typedef typename _Eng::param_type param_type;177 __save_flags<_CharT, _Traits> __lx(__is);178 typedef basic_istream<_CharT, _Traits> _Istream;179 __is.flags(_Istream::dec | _Istream::skipws);180 result_type __t;181 double __p;182 __is >> __t >> __p;183 if (!__is.fail())184 __x.param(param_type(__t, __p));185 return __is;186}187 188_LIBCPP_END_NAMESPACE_STD189 190_LIBCPP_POP_MACROS191 192#endif // _LIBCPP___CXX03___RANDOM_BINOMIAL_DISTRIBUTION_H193