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_PIECEWISE_LINEAR_DISTRIBUTION_H
10 #define _LIBCPP___RANDOM_PIECEWISE_LINEAR_DISTRIBUTION_H
11 
12 #include <__algorithm/upper_bound.h>
13 #include <__config>
14 #include <__random/is_valid.h>
15 #include <__random/uniform_real_distribution.h>
16 #include <iosfwd>
17 #include <numeric>
18 #include <vector>
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 _RealType = double>
30 class _LIBCPP_TEMPLATE_VIS piecewise_linear_distribution
31 {
32 public:
33     // types
34     typedef _RealType result_type;
35 
36     class _LIBCPP_TEMPLATE_VIS param_type
37     {
38         vector<result_type> __b_;
39         vector<result_type> __densities_;
40         vector<result_type> __areas_;
41     public:
42         typedef piecewise_linear_distribution distribution_type;
43 
44         _LIBCPP_HIDE_FROM_ABI param_type();
45         template<class _InputIteratorB, class _InputIteratorW>
46         _LIBCPP_HIDE_FROM_ABI param_type(_InputIteratorB __f_b, _InputIteratorB __l_b,
47                        _InputIteratorW __f_w);
48 #ifndef _LIBCPP_CXX03_LANG
49         template<class _UnaryOperation>
50         _LIBCPP_HIDE_FROM_ABI param_type(initializer_list<result_type> __bl, _UnaryOperation __fw);
51 #endif // _LIBCPP_CXX03_LANG
52         template<class _UnaryOperation>
53         _LIBCPP_HIDE_FROM_ABI param_type(size_t __nw, result_type __xmin, result_type __xmax,
54                        _UnaryOperation __fw);
55         _LIBCPP_HIDE_FROM_ABI param_type(param_type const&) = default;
56         _LIBCPP_HIDE_FROM_ABI param_type & operator=(const param_type& __rhs);
57 
58         _LIBCPP_INLINE_VISIBILITY
59         vector<result_type> intervals() const {return __b_;}
60         _LIBCPP_INLINE_VISIBILITY
61         vector<result_type> densities() const {return __densities_;}
62 
63         friend _LIBCPP_INLINE_VISIBILITY
64             bool operator==(const param_type& __x, const param_type& __y)
65             {return __x.__densities_ == __y.__densities_ && __x.__b_ == __y.__b_;}
66         friend _LIBCPP_INLINE_VISIBILITY
67             bool operator!=(const param_type& __x, const param_type& __y)
68             {return !(__x == __y);}
69 
70     private:
71         _LIBCPP_HIDE_FROM_ABI void __init();
72 
73         friend class piecewise_linear_distribution;
74 
75         template <class _CharT, class _Traits, class _RT>
76         friend
77         basic_ostream<_CharT, _Traits>&
78         operator<<(basic_ostream<_CharT, _Traits>& __os,
79                    const piecewise_linear_distribution<_RT>& __x);
80 
81         template <class _CharT, class _Traits, class _RT>
82         friend
83         basic_istream<_CharT, _Traits>&
84         operator>>(basic_istream<_CharT, _Traits>& __is,
85                    piecewise_linear_distribution<_RT>& __x);
86     };
87 
88 private:
89     param_type __p_;
90 
91 public:
92     // constructor and reset functions
93     _LIBCPP_INLINE_VISIBILITY
94     piecewise_linear_distribution() {}
95     template<class _InputIteratorB, class _InputIteratorW>
96         _LIBCPP_INLINE_VISIBILITY
97         piecewise_linear_distribution(_InputIteratorB __f_b,
98                                       _InputIteratorB __l_b,
99                                       _InputIteratorW __f_w)
100         : __p_(__f_b, __l_b, __f_w) {}
101 
102 #ifndef _LIBCPP_CXX03_LANG
103     template<class _UnaryOperation>
104         _LIBCPP_INLINE_VISIBILITY
105         piecewise_linear_distribution(initializer_list<result_type> __bl,
106                                       _UnaryOperation __fw)
107         : __p_(__bl, __fw) {}
108 #endif // _LIBCPP_CXX03_LANG
109 
110     template<class _UnaryOperation>
111         _LIBCPP_INLINE_VISIBILITY
112         piecewise_linear_distribution(size_t __nw, result_type __xmin,
113                                       result_type __xmax, _UnaryOperation __fw)
114         : __p_(__nw, __xmin, __xmax, __fw) {}
115 
116     _LIBCPP_INLINE_VISIBILITY
117     explicit piecewise_linear_distribution(const param_type& __p)
118         : __p_(__p) {}
119 
120     _LIBCPP_INLINE_VISIBILITY
121     void reset() {}
122 
123     // generating functions
124     template<class _URNG>
125         _LIBCPP_INLINE_VISIBILITY
126         result_type operator()(_URNG& __g)
127         {return (*this)(__g, __p_);}
128     template<class _URNG>
129     _LIBCPP_HIDE_FROM_ABI result_type operator()(_URNG& __g, const param_type& __p);
130 
131     // property functions
132     _LIBCPP_INLINE_VISIBILITY
133     vector<result_type> intervals() const {return __p_.intervals();}
134     _LIBCPP_INLINE_VISIBILITY
135     vector<result_type> densities() const {return __p_.densities();}
136 
137     _LIBCPP_INLINE_VISIBILITY
138     param_type param() const {return __p_;}
139     _LIBCPP_INLINE_VISIBILITY
140     void param(const param_type& __p) {__p_ = __p;}
141 
142     _LIBCPP_INLINE_VISIBILITY
143     result_type min() const {return __p_.__b_.front();}
144     _LIBCPP_INLINE_VISIBILITY
145     result_type max() const {return __p_.__b_.back();}
146 
147     friend _LIBCPP_INLINE_VISIBILITY
148         bool operator==(const piecewise_linear_distribution& __x,
149                         const piecewise_linear_distribution& __y)
150         {return __x.__p_ == __y.__p_;}
151     friend _LIBCPP_INLINE_VISIBILITY
152         bool operator!=(const piecewise_linear_distribution& __x,
153                         const piecewise_linear_distribution& __y)
154         {return !(__x == __y);}
155 
156     template <class _CharT, class _Traits, class _RT>
157     friend
158     basic_ostream<_CharT, _Traits>&
159     operator<<(basic_ostream<_CharT, _Traits>& __os,
160                const piecewise_linear_distribution<_RT>& __x);
161 
162     template <class _CharT, class _Traits, class _RT>
163     friend
164     basic_istream<_CharT, _Traits>&
165     operator>>(basic_istream<_CharT, _Traits>& __is,
166                piecewise_linear_distribution<_RT>& __x);
167 };
168 
169 template<class _RealType>
170 typename piecewise_linear_distribution<_RealType>::param_type &
171 piecewise_linear_distribution<_RealType>::param_type::operator=
172                                                        (const param_type& __rhs)
173 {
174 //  These can throw
175     __b_.reserve        (__rhs.__b_.size ());
176     __densities_.reserve(__rhs.__densities_.size());
177     __areas_.reserve    (__rhs.__areas_.size());
178 
179 //  These can not throw
180     __b_         = __rhs.__b_;
181     __densities_ = __rhs.__densities_;
182     __areas_     =  __rhs.__areas_;
183     return *this;
184 }
185 
186 
187 template<class _RealType>
188 void
189 piecewise_linear_distribution<_RealType>::param_type::__init()
190 {
191     __areas_.assign(__densities_.size() - 1, result_type());
192     result_type __sp = 0;
193     for (size_t __i = 0; __i < __areas_.size(); ++__i)
194     {
195         __areas_[__i] = (__densities_[__i+1] + __densities_[__i]) *
196                         (__b_[__i+1] - __b_[__i]) * .5;
197         __sp += __areas_[__i];
198     }
199     for (size_t __i = __areas_.size(); __i > 1;)
200     {
201         --__i;
202         __areas_[__i] = __areas_[__i-1] / __sp;
203     }
204     __areas_[0] = 0;
205     for (size_t __i = 1; __i < __areas_.size(); ++__i)
206         __areas_[__i] += __areas_[__i-1];
207     for (size_t __i = 0; __i < __densities_.size(); ++__i)
208         __densities_[__i] /= __sp;
209 }
210 
211 template<class _RealType>
212 piecewise_linear_distribution<_RealType>::param_type::param_type()
213     : __b_(2),
214       __densities_(2, 1.0),
215       __areas_(1, 0.0)
216 {
217     __b_[1] = 1;
218 }
219 
220 template<class _RealType>
221 template<class _InputIteratorB, class _InputIteratorW>
222 piecewise_linear_distribution<_RealType>::param_type::param_type(
223         _InputIteratorB __f_b, _InputIteratorB __l_b, _InputIteratorW __f_w)
224     : __b_(__f_b, __l_b)
225 {
226     if (__b_.size() < 2)
227     {
228         __b_.resize(2);
229         __b_[0] = 0;
230         __b_[1] = 1;
231         __densities_.assign(2, 1.0);
232         __areas_.assign(1, 0.0);
233     }
234     else
235     {
236         __densities_.reserve(__b_.size());
237         for (size_t __i = 0; __i < __b_.size(); ++__i, ++__f_w)
238             __densities_.push_back(*__f_w);
239         __init();
240     }
241 }
242 
243 #ifndef _LIBCPP_CXX03_LANG
244 
245 template<class _RealType>
246 template<class _UnaryOperation>
247 piecewise_linear_distribution<_RealType>::param_type::param_type(
248         initializer_list<result_type> __bl, _UnaryOperation __fw)
249     : __b_(__bl.begin(), __bl.end())
250 {
251     if (__b_.size() < 2)
252     {
253         __b_.resize(2);
254         __b_[0] = 0;
255         __b_[1] = 1;
256         __densities_.assign(2, 1.0);
257         __areas_.assign(1, 0.0);
258     }
259     else
260     {
261         __densities_.reserve(__b_.size());
262         for (size_t __i = 0; __i < __b_.size(); ++__i)
263             __densities_.push_back(__fw(__b_[__i]));
264         __init();
265     }
266 }
267 
268 #endif // _LIBCPP_CXX03_LANG
269 
270 template<class _RealType>
271 template<class _UnaryOperation>
272 piecewise_linear_distribution<_RealType>::param_type::param_type(
273         size_t __nw, result_type __xmin, result_type __xmax, _UnaryOperation __fw)
274     : __b_(__nw == 0 ? 2 : __nw + 1)
275 {
276     size_t __n = __b_.size() - 1;
277     result_type __d = (__xmax - __xmin) / __n;
278     __densities_.reserve(__b_.size());
279     for (size_t __i = 0; __i < __n; ++__i)
280     {
281         __b_[__i] = __xmin + __i * __d;
282         __densities_.push_back(__fw(__b_[__i]));
283     }
284     __b_[__n] = __xmax;
285     __densities_.push_back(__fw(__b_[__n]));
286     __init();
287 }
288 
289 template<class _RealType>
290 template<class _URNG>
291 _RealType
292 piecewise_linear_distribution<_RealType>::operator()(_URNG& __g, const param_type& __p)
293 {
294     static_assert(__libcpp_random_is_valid_urng<_URNG>::value, "");
295     typedef uniform_real_distribution<result_type> _Gen;
296     result_type __u = _Gen()(__g);
297     ptrdiff_t __k = _VSTD::upper_bound(__p.__areas_.begin(), __p.__areas_.end(),
298                                       __u) - __p.__areas_.begin() - 1;
299     __u -= __p.__areas_[__k];
300     const result_type __dk = __p.__densities_[__k];
301     const result_type __dk1 = __p.__densities_[__k+1];
302     const result_type __deltad = __dk1 - __dk;
303     const result_type __bk = __p.__b_[__k];
304     if (__deltad == 0)
305         return __u / __dk + __bk;
306     const result_type __bk1 = __p.__b_[__k+1];
307     const result_type __deltab = __bk1 - __bk;
308     return (__bk * __dk1 - __bk1 * __dk +
309         _VSTD::sqrt(__deltab * (__deltab * __dk * __dk + 2 * __deltad * __u))) /
310         __deltad;
311 }
312 
313 template <class _CharT, class _Traits, class _RT>
314 _LIBCPP_HIDE_FROM_ABI basic_ostream<_CharT, _Traits>&
315 operator<<(basic_ostream<_CharT, _Traits>& __os,
316            const piecewise_linear_distribution<_RT>& __x)
317 {
318     __save_flags<_CharT, _Traits> __lx(__os);
319     typedef basic_ostream<_CharT, _Traits> _OStream;
320     __os.flags(_OStream::dec | _OStream::left | _OStream::fixed |
321                _OStream::scientific);
322     _CharT __sp = __os.widen(' ');
323     __os.fill(__sp);
324     size_t __n = __x.__p_.__b_.size();
325     __os << __n;
326     for (size_t __i = 0; __i < __n; ++__i)
327         __os << __sp << __x.__p_.__b_[__i];
328     __n = __x.__p_.__densities_.size();
329     __os << __sp << __n;
330     for (size_t __i = 0; __i < __n; ++__i)
331         __os << __sp << __x.__p_.__densities_[__i];
332     __n = __x.__p_.__areas_.size();
333     __os << __sp << __n;
334     for (size_t __i = 0; __i < __n; ++__i)
335         __os << __sp << __x.__p_.__areas_[__i];
336     return __os;
337 }
338 
339 template <class _CharT, class _Traits, class _RT>
340 _LIBCPP_HIDE_FROM_ABI basic_istream<_CharT, _Traits>&
341 operator>>(basic_istream<_CharT, _Traits>& __is,
342            piecewise_linear_distribution<_RT>& __x)
343 {
344     typedef piecewise_linear_distribution<_RT> _Eng;
345     typedef typename _Eng::result_type result_type;
346     __save_flags<_CharT, _Traits> __lx(__is);
347     typedef basic_istream<_CharT, _Traits> _Istream;
348     __is.flags(_Istream::dec | _Istream::skipws);
349     size_t __n;
350     __is >> __n;
351     vector<result_type> __b(__n);
352     for (size_t __i = 0; __i < __n; ++__i)
353         __is >> __b[__i];
354     __is >> __n;
355     vector<result_type> __densities(__n);
356     for (size_t __i = 0; __i < __n; ++__i)
357         __is >> __densities[__i];
358     __is >> __n;
359     vector<result_type> __areas(__n);
360     for (size_t __i = 0; __i < __n; ++__i)
361         __is >> __areas[__i];
362     if (!__is.fail())
363     {
364         swap(__x.__p_.__b_, __b);
365         swap(__x.__p_.__densities_, __densities);
366         swap(__x.__p_.__areas_, __areas);
367     }
368     return __is;
369 }
370 
371 _LIBCPP_END_NAMESPACE_STD
372 
373 _LIBCPP_POP_MACROS
374 
375 #endif // _LIBCPP___RANDOM_PIECEWISE_LINEAR_DISTRIBUTION_H
376