1 | /* boost random/additive_combine.hpp header file |
2 | * |
3 | * Copyright Jens Maurer 2000-2001 |
4 | * Distributed under the Boost Software License, Version 1.0. (See |
5 | * accompanying file LICENSE_1_0.txt or copy at |
6 | * http://www.boost.org/LICENSE_1_0.txt) |
7 | * |
8 | * See http://www.boost.org for most recent version including documentation. |
9 | * |
10 | * $Id$ |
11 | * |
12 | * Revision history |
13 | * 2001-02-18 moved to individual header files |
14 | */ |
15 | |
16 | #ifndef BOOST_RANDOM_ADDITIVE_COMBINE_HPP |
17 | #define BOOST_RANDOM_ADDITIVE_COMBINE_HPP |
18 | |
19 | #include <istream> |
20 | #include <iosfwd> |
21 | #include <algorithm> // for std::min and std::max |
22 | #include <boost/config.hpp> |
23 | #include <boost/cstdint.hpp> |
24 | #include <boost/random/detail/config.hpp> |
25 | #include <boost/random/detail/operators.hpp> |
26 | #include <boost/random/detail/seed.hpp> |
27 | #include <boost/random/linear_congruential.hpp> |
28 | |
29 | namespace boost { |
30 | namespace random { |
31 | |
32 | /** |
33 | * An instantiation of class template @c additive_combine_engine models a |
34 | * \pseudo_random_number_generator. It combines two multiplicative |
35 | * \linear_congruential_engine number generators, i.e. those with @c c = 0. |
36 | * It is described in |
37 | * |
38 | * @blockquote |
39 | * "Efficient and Portable Combined Random Number Generators", Pierre L'Ecuyer, |
40 | * Communications of the ACM, Vol. 31, No. 6, June 1988, pp. 742-749, 774 |
41 | * @endblockquote |
42 | * |
43 | * The template parameters MLCG1 and MLCG2 shall denote two different |
44 | * \linear_congruential_engine number generators, each with c = 0. Each |
45 | * invocation returns a random number |
46 | * X(n) := (MLCG1(n) - MLCG2(n)) mod (m1 - 1), |
47 | * where m1 denotes the modulus of MLCG1. |
48 | */ |
49 | template<class MLCG1, class MLCG2> |
50 | class additive_combine_engine |
51 | { |
52 | public: |
53 | typedef MLCG1 first_base; |
54 | typedef MLCG2 second_base; |
55 | typedef typename MLCG1::result_type result_type; |
56 | |
57 | // Required by old Boost.Random concept |
58 | BOOST_STATIC_CONSTANT(bool, has_fixed_range = false); |
59 | /** |
60 | * Returns the smallest value that the generator can produce |
61 | */ |
62 | static result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () |
63 | { return 1; } |
64 | /** |
65 | * Returns the largest value that the generator can produce |
66 | */ |
67 | static result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () |
68 | { return MLCG1::modulus-1; } |
69 | |
70 | /** |
71 | * Constructs an @c additive_combine_engine using the |
72 | * default constructors of the two base generators. |
73 | */ |
74 | additive_combine_engine() : _mlcg1(), _mlcg2() { } |
75 | /** |
76 | * Constructs an @c additive_combine_engine, using seed as |
77 | * the constructor argument for both base generators. |
78 | */ |
79 | BOOST_RANDOM_DETAIL_ARITHMETIC_CONSTRUCTOR(additive_combine_engine, |
80 | result_type, seed_arg) |
81 | { |
82 | _mlcg1.seed(seed_arg); |
83 | _mlcg2.seed(seed_arg); |
84 | } |
85 | /** |
86 | * Constructs an @c additive_combine_engine, using seq as |
87 | * the constructor argument for both base generators. |
88 | * |
89 | * @xmlwarning |
90 | * The semantics of this function are liable to change. |
91 | * A @c seed_seq is designed to generate all the seeds |
92 | * in one shot, but this seeds the two base engines |
93 | * independantly and probably ends up giving the same |
94 | * sequence to both. |
95 | * @endxmlwarning |
96 | */ |
97 | BOOST_RANDOM_DETAIL_SEED_SEQ_CONSTRUCTOR(additive_combine_engine, |
98 | SeedSeq, seq) |
99 | { |
100 | _mlcg1.seed(seq); |
101 | _mlcg2.seed(seq); |
102 | } |
103 | /** |
104 | * Constructs an @c additive_combine_engine, using |
105 | * @c seed1 and @c seed2 as the constructor argument to |
106 | * the first and second base generators, respectively. |
107 | */ |
108 | additive_combine_engine(typename MLCG1::result_type seed1, |
109 | typename MLCG2::result_type seed2) |
110 | : _mlcg1(seed1), _mlcg2(seed2) { } |
111 | /** |
112 | * Contructs an @c additive_combine_engine with |
113 | * values from the range defined by the input iterators first |
114 | * and last. first will be modified to point to the element |
115 | * after the last one used. |
116 | * |
117 | * Throws: @c std::invalid_argument if the input range is too small. |
118 | * |
119 | * Exception Safety: Basic |
120 | */ |
121 | template<class It> additive_combine_engine(It& first, It last) |
122 | : _mlcg1(first, last), _mlcg2(first, last) { } |
123 | |
124 | /** |
125 | * Seeds an @c additive_combine_engine using the default |
126 | * seeds of the two base generators. |
127 | */ |
128 | void seed() |
129 | { |
130 | _mlcg1.seed(); |
131 | _mlcg2.seed(); |
132 | } |
133 | |
134 | /** |
135 | * Seeds an @c additive_combine_engine, using @c seed as the |
136 | * seed for both base generators. |
137 | */ |
138 | BOOST_RANDOM_DETAIL_ARITHMETIC_SEED(additive_combine_engine, |
139 | result_type, seed_arg) |
140 | { |
141 | _mlcg1.seed(seed_arg); |
142 | _mlcg2.seed(seed_arg); |
143 | } |
144 | |
145 | /** |
146 | * Seeds an @c additive_combine_engine, using @c seq to |
147 | * seed both base generators. |
148 | * |
149 | * See the warning on the corresponding constructor. |
150 | */ |
151 | BOOST_RANDOM_DETAIL_SEED_SEQ_SEED(additive_combine_engine, |
152 | SeedSeq, seq) |
153 | { |
154 | _mlcg1.seed(seq); |
155 | _mlcg2.seed(seq); |
156 | } |
157 | |
158 | /** |
159 | * Seeds an @c additive_combine generator, using @c seed1 and @c seed2 as |
160 | * the seeds to the first and second base generators, respectively. |
161 | */ |
162 | void seed(typename MLCG1::result_type seed1, |
163 | typename MLCG2::result_type seed2) |
164 | { |
165 | _mlcg1.seed(seed1); |
166 | _mlcg2.seed(seed2); |
167 | } |
168 | |
169 | /** |
170 | * Seeds an @c additive_combine_engine with |
171 | * values from the range defined by the input iterators first |
172 | * and last. first will be modified to point to the element |
173 | * after the last one used. |
174 | * |
175 | * Throws: @c std::invalid_argument if the input range is too small. |
176 | * |
177 | * Exception Safety: Basic |
178 | */ |
179 | template<class It> void seed(It& first, It last) |
180 | { |
181 | _mlcg1.seed(first, last); |
182 | _mlcg2.seed(first, last); |
183 | } |
184 | |
185 | /** Returns the next value of the generator. */ |
186 | result_type operator()() { |
187 | result_type val1 = _mlcg1(); |
188 | result_type val2 = _mlcg2(); |
189 | if(val2 < val1) return val1 - val2; |
190 | else return val1 - val2 + MLCG1::modulus - 1; |
191 | } |
192 | |
193 | /** Fills a range with random values */ |
194 | template<class Iter> |
195 | void generate(Iter first, Iter last) |
196 | { detail::generate_from_int(*this, first, last); } |
197 | |
198 | /** Advances the state of the generator by @c z. */ |
199 | void discard(boost::uintmax_t z) |
200 | { |
201 | _mlcg1.discard(z); |
202 | _mlcg2.discard(z); |
203 | } |
204 | |
205 | /** |
206 | * Writes the state of an @c additive_combine_engine to a @c |
207 | * std::ostream. The textual representation of an @c |
208 | * additive_combine_engine is the textual representation of |
209 | * the first base generator followed by the textual representation |
210 | * of the second base generator. |
211 | */ |
212 | BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, additive_combine_engine, r) |
213 | { os << r._mlcg1 << ' ' << r._mlcg2; return os; } |
214 | |
215 | /** |
216 | * Reads the state of an @c additive_combine_engine from a |
217 | * @c std::istream. |
218 | */ |
219 | BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, additive_combine_engine, r) |
220 | { is >> r._mlcg1 >> std::ws >> r._mlcg2; return is; } |
221 | |
222 | /** |
223 | * Returns: true iff the two @c additive_combine_engines will |
224 | * produce the same sequence of values. |
225 | */ |
226 | BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(additive_combine_engine, x, y) |
227 | { return x._mlcg1 == y._mlcg1 && x._mlcg2 == y._mlcg2; } |
228 | /** |
229 | * Returns: true iff the two @c additive_combine_engines will |
230 | * produce different sequences of values. |
231 | */ |
232 | BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(additive_combine_engine) |
233 | |
234 | private: |
235 | MLCG1 _mlcg1; |
236 | MLCG2 _mlcg2; |
237 | }; |
238 | |
239 | #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION |
240 | template<class MLCG1, class MLCG2> |
241 | const bool additive_combine_engine<MLCG1, MLCG2>::has_fixed_range; |
242 | #endif |
243 | |
244 | /// \cond show_deprecated |
245 | |
246 | /** Provided for backwards compatibility. */ |
247 | template<class MLCG1, class MLCG2, typename MLCG1::result_type val = 0> |
248 | class additive_combine : public additive_combine_engine<MLCG1, MLCG2> |
249 | { |
250 | typedef additive_combine_engine<MLCG1, MLCG2> base_t; |
251 | public: |
252 | typedef typename base_t::result_type result_type; |
253 | additive_combine() {} |
254 | template<class T> |
255 | additive_combine(T& arg) : base_t(arg) {} |
256 | template<class T> |
257 | additive_combine(const T& arg) : base_t(arg) {} |
258 | template<class It> |
259 | additive_combine(It& first, It last) : base_t(first, last) {} |
260 | }; |
261 | |
262 | /// \endcond |
263 | |
264 | /** |
265 | * The specialization \ecuyer1988 was suggested in |
266 | * |
267 | * @blockquote |
268 | * "Efficient and Portable Combined Random Number Generators", Pierre L'Ecuyer, |
269 | * Communications of the ACM, Vol. 31, No. 6, June 1988, pp. 742-749, 774 |
270 | * @endblockquote |
271 | */ |
272 | typedef additive_combine_engine< |
273 | linear_congruential_engine<uint32_t, 40014, 0, 2147483563>, |
274 | linear_congruential_engine<uint32_t, 40692, 0, 2147483399> |
275 | > ecuyer1988; |
276 | |
277 | } // namespace random |
278 | |
279 | using random::ecuyer1988; |
280 | |
281 | } // namespace boost |
282 | |
283 | #endif // BOOST_RANDOM_ADDITIVE_COMBINE_HPP |
284 | |