1 | /* boost random/shuffle_order.hpp header file |
2 | * |
3 | * Copyright Jens Maurer 2000-2001 |
4 | * Copyright Steven Watanabe 2010 |
5 | * Distributed under the Boost Software License, Version 1.0. (See |
6 | * accompanying file LICENSE_1_0.txt or copy at |
7 | * http://www.boost.org/LICENSE_1_0.txt) |
8 | * |
9 | * See http://www.boost.org for most recent version including documentation. |
10 | * |
11 | * $Id$ |
12 | * |
13 | */ |
14 | |
15 | #ifndef BOOST_RANDOM_SHUFFLE_ORDER_HPP |
16 | #define BOOST_RANDOM_SHUFFLE_ORDER_HPP |
17 | |
18 | #include <iostream> |
19 | #include <algorithm> // std::copy |
20 | #include <cassert> |
21 | #include <boost/config.hpp> |
22 | #include <boost/limits.hpp> |
23 | #include <boost/static_assert.hpp> |
24 | #include <boost/cstdint.hpp> |
25 | #include <boost/random/detail/operators.hpp> |
26 | #include <boost/random/detail/seed.hpp> |
27 | #include <boost/random/detail/signed_unsigned_tools.hpp> |
28 | #include <boost/random/linear_congruential.hpp> |
29 | |
30 | #include <boost/random/detail/disable_warnings.hpp> |
31 | |
32 | namespace boost { |
33 | namespace random { |
34 | |
35 | /** |
36 | * Instatiations of class template @c shuffle_order_engine model a |
37 | * \pseudo_random_number_generator. It mixes the output |
38 | * of some (usually \linear_congruential_engine) |
39 | * \uniform_random_number_generator to get better statistical properties. |
40 | * The algorithm is described in |
41 | * |
42 | * @blockquote |
43 | * "Improving a poor random number generator", Carter Bays |
44 | * and S.D. Durham, ACM Transactions on Mathematical Software, |
45 | * Vol 2, No. 1, March 1976, pp. 59-64. |
46 | * http://doi.acm.org/10.1145/355666.355670 |
47 | * @endblockquote |
48 | * |
49 | * The output of the base generator is buffered in an array of |
50 | * length k. Every output X(n) has a second role: It gives an |
51 | * index into the array where X(n+1) will be retrieved. Used |
52 | * array elements are replaced with fresh output from the base |
53 | * generator. |
54 | * |
55 | * Template parameters are the base generator and the array |
56 | * length k, which should be around 100. |
57 | */ |
58 | template<class UniformRandomNumberGenerator, std::size_t k> |
59 | class shuffle_order_engine |
60 | { |
61 | public: |
62 | typedef UniformRandomNumberGenerator base_type; |
63 | typedef typename base_type::result_type result_type; |
64 | |
65 | BOOST_STATIC_CONSTANT(bool, has_fixed_range = false); |
66 | BOOST_STATIC_CONSTANT(std::size_t, buffer_size = k); |
67 | BOOST_STATIC_CONSTANT(std::size_t, table_size = k); |
68 | |
69 | BOOST_STATIC_ASSERT(std::numeric_limits<result_type>::is_integer); |
70 | BOOST_STATIC_ASSERT(k > 0); |
71 | |
72 | /** |
73 | * Constructs a @c shuffle_order_engine by invoking the |
74 | * default constructor of the base generator. |
75 | * |
76 | * Complexity: Exactly k+1 invocations of the base generator. |
77 | */ |
78 | shuffle_order_engine() : _rng() { init(); } |
79 | /** |
80 | * Constructs a @c shuffle_output_engine by invoking the one-argument |
81 | * constructor of the base generator with the parameter seed. |
82 | * |
83 | * Complexity: Exactly k+1 invocations of the base generator. |
84 | */ |
85 | BOOST_RANDOM_DETAIL_ARITHMETIC_CONSTRUCTOR(shuffle_order_engine, |
86 | result_type, s) |
87 | { _rng.seed(s); init(); } |
88 | BOOST_RANDOM_DETAIL_SEED_SEQ_CONSTRUCTOR(shuffle_order_engine, SeedSeq, seq) |
89 | { _rng.seed(seq); init(); } |
90 | /** |
91 | * Constructs a @c shuffle_output_engine by using a copy |
92 | * of the provided generator. |
93 | * |
94 | * Precondition: The template argument UniformRandomNumberGenerator |
95 | * shall denote a CopyConstructible type. |
96 | * |
97 | * Complexity: Exactly k+1 invocations of the base generator. |
98 | */ |
99 | explicit shuffle_order_engine(const base_type & rng) : _rng(rng) { init(); } |
100 | |
101 | #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES |
102 | explicit shuffle_order_engine(base_type&& rng) : _rng(rng) { init(); } |
103 | #endif |
104 | |
105 | template<class It> shuffle_order_engine(It& first, It last) |
106 | : _rng(first, last) { init(); } |
107 | void seed() { _rng.seed(); init(); } |
108 | /** |
109 | * Invokes the one-argument seed method of the base generator |
110 | * with the parameter seed and re-initializes the internal buffer array. |
111 | * |
112 | * Complexity: Exactly k+1 invocations of the base generator. |
113 | */ |
114 | BOOST_RANDOM_DETAIL_ARITHMETIC_SEED(shuffle_order_engine, |
115 | result_type, seed_arg) |
116 | { _rng.seed(seed_arg); init(); } |
117 | /** |
118 | * Invokes the one-argument seed method of the base generator |
119 | * with the parameter seq and re-initializes the internal buffer array. |
120 | * |
121 | * Complexity: Exactly k+1 invocations of the base generator. |
122 | */ |
123 | BOOST_RANDOM_DETAIL_SEED_SEQ_SEED(shuffle_order_engine, SeedSeq, seq) |
124 | { _rng.seed(seq); init(); } |
125 | template<class It> void seed(It& first, It last) |
126 | { _rng.seed(first, last); init(); } |
127 | |
128 | const base_type& base() const { return _rng; } |
129 | |
130 | result_type operator()() { |
131 | // calculating the range every time may seem wasteful. However, this |
132 | // makes the information locally available for the optimizer. |
133 | typedef typename boost::random::traits::make_unsigned<result_type>::type base_unsigned; |
134 | const base_unsigned brange = |
135 | detail::subtract<result_type>()((max)(), (min)()); |
136 | const base_unsigned off = |
137 | detail::subtract<result_type>()(y, (min)()); |
138 | |
139 | base_unsigned j; |
140 | if(k == 1) { |
141 | j = 0; |
142 | } else if(brange < (std::numeric_limits<base_unsigned>::max)() / k) { |
143 | // try to do it in the native type if we know that it won't |
144 | // overflow |
145 | j = k * off / (brange + 1); |
146 | } else if(brange < (std::numeric_limits<uintmax_t>::max)() / k) { |
147 | // Otherwise try to use uint64_t |
148 | j = static_cast<base_unsigned>( |
149 | static_cast<uintmax_t>(off) * k / |
150 | (static_cast<uintmax_t>(brange) + 1)); |
151 | } else { |
152 | boost::uintmax_t divisor = |
153 | static_cast<boost::uintmax_t>(brange) + 1; |
154 | j = static_cast<base_unsigned>(detail::muldiv(off, k, divisor)); |
155 | } |
156 | // assert(0 <= j && j < k); |
157 | y = v[j]; |
158 | v[j] = _rng(); |
159 | return y; |
160 | } |
161 | |
162 | /** Advances the generator by z steps. */ |
163 | void discard(boost::uintmax_t z) |
164 | { |
165 | for(boost::uintmax_t j = 0; j < z; ++j) { |
166 | (*this)(); |
167 | } |
168 | } |
169 | |
170 | /** Fills a range with pseudo-random values. */ |
171 | template<class Iter> |
172 | void generate(Iter first, Iter last) |
173 | { detail::generate_from_int(*this, first, last); } |
174 | |
175 | /** Returns the smallest value that the generator can produce. */ |
176 | static result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () |
177 | { return (base_type::min)(); } |
178 | /** Returns the largest value that the generator can produce. */ |
179 | static result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () |
180 | { return (base_type::max)(); } |
181 | |
182 | /** Writes a @c shuffle_order_engine to a @c std::ostream. */ |
183 | BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, shuffle_order_engine, s) |
184 | { |
185 | os << s._rng; |
186 | for(std::size_t i = 0; i < k; ++i) |
187 | os << ' ' << s.v[i]; |
188 | os << ' ' << s.y; |
189 | return os; |
190 | } |
191 | |
192 | /** Reads a @c shuffle_order_engine from a @c std::istream. */ |
193 | BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, shuffle_order_engine, s) |
194 | { |
195 | is >> s._rng; |
196 | for(std::size_t i = 0; i < k; ++i) |
197 | is >> std::ws >> s.v[i]; |
198 | is >> std::ws >> s.y; |
199 | return is; |
200 | } |
201 | |
202 | /** Returns true if the two generators will produce identical sequences. */ |
203 | BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(shuffle_order_engine, x, y) |
204 | { return x._rng == y._rng && x.y == y.y && std::equal(x.v, x.v+k, y.v); } |
205 | /** Returns true if the two generators will produce different sequences. */ |
206 | BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(shuffle_order_engine) |
207 | |
208 | private: |
209 | |
210 | /// \cond show_private |
211 | |
212 | void init() |
213 | { |
214 | // we cannot use std::generate, because it uses pass-by-value for _rng |
215 | for(result_type * p = v; p != v+k; ++p) |
216 | *p = _rng(); |
217 | y = _rng(); |
218 | } |
219 | |
220 | /// \endcond |
221 | |
222 | base_type _rng; |
223 | result_type v[k]; |
224 | result_type y; |
225 | }; |
226 | |
227 | #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION |
228 | // A definition is required even for integral static constants |
229 | template<class URNG, std::size_t k> |
230 | const bool shuffle_order_engine<URNG, k>::has_fixed_range; |
231 | template<class URNG, std::size_t k> |
232 | const std::size_t shuffle_order_engine<URNG, k>::table_size; |
233 | template<class URNG, std::size_t k> |
234 | const std::size_t shuffle_order_engine<URNG, k>::buffer_size; |
235 | #endif |
236 | |
237 | /** |
238 | * According to Harry Erwin (private e-mail), the specialization |
239 | * @c kreutzer1986 was suggested in: |
240 | * |
241 | * @blockquote |
242 | * "System Simulation: Programming Styles and Languages (International |
243 | * Computer Science Series)", Wolfgang Kreutzer, Addison-Wesley, December 1986. |
244 | * @endblockquote |
245 | */ |
246 | typedef shuffle_order_engine< |
247 | linear_congruential_engine<uint32_t, 1366, 150889, 714025>, |
248 | 97> kreutzer1986; |
249 | |
250 | /** |
251 | * The specialization @c knuth_b is specified by the C++ standard. |
252 | * It is described in |
253 | * |
254 | * @blockquote |
255 | * "The Art of Computer Programming, Second Edition, Volume 2, |
256 | * Seminumerical Algorithms", Donald Knuth, Addison-Wesley, 1981. |
257 | * @endblockquote |
258 | */ |
259 | typedef shuffle_order_engine<minstd_rand0, 256> knuth_b; |
260 | |
261 | } // namespace random |
262 | |
263 | using random::kreutzer1986; |
264 | |
265 | } // namespace boost |
266 | |
267 | #include <boost/random/detail/enable_warnings.hpp> |
268 | |
269 | #endif // BOOST_RANDOM_SHUFFLE_OUTPUT_HPP |
270 | |