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1 | /* boost random/xor_combine.hpp header file |
2 | * | |
3 | * Copyright Jens Maurer 2002 | |
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 | */ | |
13 | ||
14 | #ifndef BOOST_RANDOM_XOR_COMBINE_HPP | |
15 | #define BOOST_RANDOM_XOR_COMBINE_HPP | |
16 | ||
17 | #include <istream> | |
18 | #include <iosfwd> | |
19 | #include <cassert> | |
20 | #include <algorithm> // for std::min and std::max | |
21 | #include <boost/config.hpp> | |
22 | #include <boost/limits.hpp> | |
23 | #include <boost/cstdint.hpp> // uint32_t | |
24 | #include <boost/random/detail/config.hpp> | |
25 | #include <boost/random/detail/seed.hpp> | |
26 | #include <boost/random/detail/seed_impl.hpp> | |
27 | #include <boost/random/detail/operators.hpp> | |
28 | ||
29 | namespace boost { | |
30 | namespace random { | |
31 | ||
32 | /** | |
33 | * Instantiations of @c xor_combine_engine model a | |
34 | * \pseudo_random_number_generator. To produce its output it | |
35 | * invokes each of the base generators, shifts their results | |
36 | * and xors them together. | |
37 | */ | |
38 | template<class URNG1, int s1, class URNG2, int s2> | |
39 | class xor_combine_engine | |
40 | { | |
41 | public: | |
42 | typedef URNG1 base1_type; | |
43 | typedef URNG2 base2_type; | |
44 | typedef typename base1_type::result_type result_type; | |
45 | ||
46 | BOOST_STATIC_CONSTANT(bool, has_fixed_range = false); | |
47 | BOOST_STATIC_CONSTANT(int, shift1 = s1); | |
48 | BOOST_STATIC_CONSTANT(int, shift2 = s2); | |
49 | ||
50 | /** | |
51 | * Constructors a @c xor_combine_engine by default constructing | |
52 | * both base generators. | |
53 | */ | |
54 | xor_combine_engine() : _rng1(), _rng2() { } | |
55 | ||
56 | /** Constructs a @c xor_combine by copying two base generators. */ | |
57 | xor_combine_engine(const base1_type & rng1, const base2_type & rng2) | |
58 | : _rng1(rng1), _rng2(rng2) { } | |
59 | ||
60 | /** | |
61 | * Constructs a @c xor_combine_engine, seeding both base generators | |
62 | * with @c v. | |
63 | * | |
64 | * @xmlwarning | |
65 | * The exact algorithm used by this function may change in the future. | |
66 | * @endxmlwarning | |
67 | */ | |
68 | BOOST_RANDOM_DETAIL_ARITHMETIC_CONSTRUCTOR(xor_combine_engine, | |
69 | result_type, v) | |
70 | { seed(v); } | |
71 | ||
72 | /** | |
73 | * Constructs a @c xor_combine_engine, seeding both base generators | |
74 | * with values produced by @c seq. | |
75 | */ | |
76 | BOOST_RANDOM_DETAIL_SEED_SEQ_CONSTRUCTOR(xor_combine_engine, | |
77 | SeedSeq, seq) | |
78 | { seed(seq); } | |
79 | ||
80 | /** | |
81 | * Constructs a @c xor_combine_engine, seeding both base generators | |
82 | * with values from the iterator range [first, last) and changes | |
83 | * first to point to the element after the last one used. If there | |
84 | * are not enough elements in the range to seed both generators, | |
85 | * throws @c std::invalid_argument. | |
86 | */ | |
87 | template<class It> xor_combine_engine(It& first, It last) | |
88 | : _rng1(first, last), _rng2( /* advanced by other call */ first, last) { } | |
89 | ||
90 | /** Calls @c seed() for both base generators. */ | |
91 | void seed() { _rng1.seed(); _rng2.seed(); } | |
92 | ||
93 | /** @c seeds both base generators with @c v. */ | |
94 | BOOST_RANDOM_DETAIL_ARITHMETIC_SEED(xor_combine_engine, result_type, v) | |
95 | { _rng1.seed(v); _rng2.seed(v); } | |
96 | ||
97 | /** @c seeds both base generators with values produced by @c seq. */ | |
98 | BOOST_RANDOM_DETAIL_SEED_SEQ_SEED(xor_combine_engine, SeedSeq, seq) | |
99 | { _rng1.seed(seq); _rng2.seed(seq); } | |
100 | ||
101 | /** | |
102 | * seeds both base generators with values from the iterator | |
103 | * range [first, last) and changes first to point to the element | |
104 | * after the last one used. If there are not enough elements in | |
105 | * the range to seed both generators, throws @c std::invalid_argument. | |
106 | */ | |
107 | template<class It> void seed(It& first, It last) | |
108 | { | |
109 | _rng1.seed(first, last); | |
110 | _rng2.seed(first, last); | |
111 | } | |
112 | ||
113 | /** Returns the first base generator. */ | |
114 | const base1_type& base1() const { return _rng1; } | |
115 | ||
116 | /** Returns the second base generator. */ | |
117 | const base2_type& base2() const { return _rng2; } | |
118 | ||
119 | /** Returns the next value of the generator. */ | |
120 | result_type operator()() | |
121 | { | |
122 | return (_rng1() << s1) ^ (_rng2() << s2); | |
123 | } | |
124 | ||
125 | /** Fills a range with random values */ | |
126 | template<class Iter> | |
127 | void generate(Iter first, Iter last) | |
128 | { detail::generate_from_int(*this, first, last); } | |
129 | ||
130 | /** Advances the state of the generator by @c z. */ | |
131 | void discard(boost::uintmax_t z) | |
132 | { | |
133 | _rng1.discard(z); | |
134 | _rng2.discard(z); | |
135 | } | |
136 | ||
137 | /** Returns the smallest value that the generator can produce. */ | |
138 | static result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () { return (std::min)((URNG1::min)(), (URNG2::min)()); } | |
139 | /** Returns the largest value that the generator can produce. */ | |
140 | static result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () { return (std::max)((URNG1::min)(), (URNG2::max)()); } | |
141 | ||
142 | /** | |
143 | * Writes the textual representation of the generator to a @c std::ostream. | |
144 | */ | |
145 | BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, xor_combine_engine, s) | |
146 | { | |
147 | os << s._rng1 << ' ' << s._rng2; | |
148 | return os; | |
149 | } | |
150 | ||
151 | /** | |
152 | * Reads the textual representation of the generator from a @c std::istream. | |
153 | */ | |
154 | BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, xor_combine_engine, s) | |
155 | { | |
156 | is >> s._rng1 >> std::ws >> s._rng2; | |
157 | return is; | |
158 | } | |
159 | ||
160 | /** Returns true if the two generators will produce identical sequences. */ | |
161 | BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(xor_combine_engine, x, y) | |
162 | { return x._rng1 == y._rng1 && x._rng2 == y._rng2; } | |
163 | ||
164 | /** Returns true if the two generators will produce different sequences. */ | |
165 | BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(xor_combine_engine) | |
166 | ||
167 | private: | |
168 | base1_type _rng1; | |
169 | base2_type _rng2; | |
170 | }; | |
171 | ||
172 | #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION | |
173 | // A definition is required even for integral static constants | |
174 | template<class URNG1, int s1, class URNG2, int s2> | |
175 | const bool xor_combine_engine<URNG1, s1, URNG2, s2>::has_fixed_range; | |
176 | template<class URNG1, int s1, class URNG2, int s2> | |
177 | const int xor_combine_engine<URNG1, s1, URNG2, s2>::shift1; | |
178 | template<class URNG1, int s1, class URNG2, int s2> | |
179 | const int xor_combine_engine<URNG1, s1, URNG2, s2>::shift2; | |
180 | #endif | |
181 | ||
182 | /// \cond show_private | |
183 | ||
184 | /** Provided for backwards compatibility. */ | |
185 | template<class URNG1, int s1, class URNG2, int s2, | |
186 | typename URNG1::result_type v = 0> | |
187 | class xor_combine : public xor_combine_engine<URNG1, s1, URNG2, s2> | |
188 | { | |
189 | typedef xor_combine_engine<URNG1, s1, URNG2, s2> base_type; | |
190 | public: | |
191 | typedef typename base_type::result_type result_type; | |
192 | xor_combine() {} | |
193 | xor_combine(result_type val) : base_type(val) {} | |
194 | template<class It> | |
195 | xor_combine(It& first, It last) : base_type(first, last) {} | |
196 | xor_combine(const URNG1 & rng1, const URNG2 & rng2) | |
197 | : base_type(rng1, rng2) { } | |
198 | ||
199 | result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return (std::min)((this->base1().min)(), (this->base2().min)()); } | |
200 | result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return (std::max)((this->base1().min)(), (this->base2().max)()); } | |
201 | }; | |
202 | ||
203 | /// \endcond | |
204 | ||
205 | } // namespace random | |
206 | } // namespace boost | |
207 | ||
208 | #endif // BOOST_RANDOM_XOR_COMBINE_HPP |