libcxx/include/__random/negative_binomial_distribution.h

   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
  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
  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
  56 private:
  57   param_type __p_;
  58
  59 public:
  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
  99 template <class _IntType>
 100 template <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
 125 template <class _CharT, class _Traits, class _IntType>
 126 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
 127 operator<<(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
 136 template <class _CharT, class _Traits, class _IntType>
 137 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
 138 operator>>(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