1 | /* boost random/linear_feedback_shift.hpp header file |
2 | * |
3 | * Copyright Jens Maurer 2002 |
4 | * Copyright Steven Watanabe 2011 |
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_LINEAR_FEEDBACK_SHIFT_HPP |
16 | #define BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP |
17 | |
18 | #include <iosfwd> |
19 | #include <stdexcept> |
20 | #include <boost/config.hpp> |
21 | #include <boost/cstdint.hpp> |
22 | #include <boost/static_assert.hpp> |
23 | #include <boost/integer/integer_mask.hpp> |
24 | #include <boost/random/detail/config.hpp> |
25 | #include <boost/random/detail/seed.hpp> |
26 | #include <boost/random/detail/operators.hpp> |
27 | #include <boost/random/detail/seed_impl.hpp> |
28 | |
29 | namespace boost { |
30 | namespace random { |
31 | |
32 | /** |
33 | * Instatiations of @c linear_feedback_shift model a |
34 | * \pseudo_random_number_generator. It was originally |
35 | * proposed in |
36 | * |
37 | * @blockquote |
38 | * "Random numbers generated by linear recurrence modulo two.", |
39 | * Tausworthe, R. C.(1965), Mathematics of Computation 19, 201-209. |
40 | * @endblockquote |
41 | */ |
42 | template<class UIntType, int w, int k, int q, int s> |
43 | class linear_feedback_shift_engine |
44 | { |
45 | public: |
46 | typedef UIntType result_type; |
47 | BOOST_STATIC_CONSTANT(bool, has_fixed_range = false); |
48 | BOOST_STATIC_CONSTANT(int, word_size = w); |
49 | BOOST_STATIC_CONSTANT(int, exponent1 = k); |
50 | BOOST_STATIC_CONSTANT(int, exponent2 = q); |
51 | BOOST_STATIC_CONSTANT(int, step_size = s); |
52 | BOOST_STATIC_CONSTANT(UIntType, default_seed = 341); |
53 | |
54 | /** Returns the smallest value that the generator can produce. */ |
55 | static result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () { return 0; } |
56 | /** Returns the largest value that the generator can produce. */ |
57 | static result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () |
58 | { return wordmask(); } |
59 | |
60 | BOOST_STATIC_ASSERT(w > 0); |
61 | BOOST_STATIC_ASSERT(q > 0); |
62 | BOOST_STATIC_ASSERT(k < w); |
63 | BOOST_STATIC_ASSERT(0 < 2*q && 2*q < k); |
64 | BOOST_STATIC_ASSERT(0 < s && s <= k-q); |
65 | |
66 | /** Constructs a @c linear_feedback_shift_engine, using the default seed. */ |
67 | linear_feedback_shift_engine() { seed(); } |
68 | |
69 | /** Constructs a @c linear_feedback_shift_engine, seeding it with s0. */ |
70 | BOOST_RANDOM_DETAIL_ARITHMETIC_CONSTRUCTOR(linear_feedback_shift_engine, |
71 | UIntType, s0) |
72 | { seed(s0); } |
73 | |
74 | /** Constructs a @c linear_feedback_shift_engine, seeding it with seq. */ |
75 | BOOST_RANDOM_DETAIL_SEED_SEQ_CONSTRUCTOR(linear_feedback_shift_engine, |
76 | SeedSeq, seq) |
77 | { seed(seq); } |
78 | |
79 | /** |
80 | * Constructs a @c linear_feedback_shift_engine, seeding it with |
81 | * values from the range [first, last). |
82 | */ |
83 | template<class It> linear_feedback_shift_engine(It& first, It last) |
84 | { seed(first, last); } |
85 | |
86 | /** Seeds a @c linear_feedback_shift_engine with the default seed. */ |
87 | void seed() { seed(default_seed); } |
88 | |
89 | /** Seeds a @c linear_feedback_shift_engine with @c s0. */ |
90 | BOOST_RANDOM_DETAIL_ARITHMETIC_SEED(linear_feedback_shift_engine, |
91 | UIntType, s0) |
92 | { |
93 | value = s0 & wordmask(); |
94 | if(value < (1 << (w-k))) { |
95 | value += 1 << (w-k); |
96 | } |
97 | } |
98 | |
99 | /** |
100 | * Seeds a @c linear_feedback_shift_engine with values |
101 | * produced by @c seq.generate(). |
102 | */ |
103 | BOOST_RANDOM_DETAIL_SEED_SEQ_SEED(linear_feedback_shift_engine, |
104 | SeedSeq, seq) |
105 | { seed(detail::seed_one_int<UIntType, (UIntType(2) << (w - 1))>(seq)); } |
106 | |
107 | /** |
108 | * Seeds a @c linear_feedback_shift_engine with values |
109 | * from the range [first, last). |
110 | */ |
111 | template<class It> void seed(It& first, It last) |
112 | { |
113 | seed(detail::get_one_int<UIntType, (UIntType(2) << (w - 1))>(first, last)); |
114 | } |
115 | |
116 | /** Returns the next value of the generator. */ |
117 | result_type operator()() |
118 | { |
119 | const UIntType b = (((value << q) ^ value) & wordmask()) >> (k-s); |
120 | const UIntType mask = (wordmask() << (w-k)) & wordmask(); |
121 | value = ((value & mask) << s) ^ b; |
122 | return value; |
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 | for(boost::uintmax_t j = 0; j < z; ++j) { |
134 | (*this)(); |
135 | } |
136 | } |
137 | |
138 | /** |
139 | * Writes the textual representation of the generator to a @c std::ostream. |
140 | */ |
141 | BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, linear_feedback_shift_engine, x) |
142 | { |
143 | os << x.value; |
144 | return os; |
145 | } |
146 | |
147 | /** |
148 | * Reads the textual representation of the generator from a @c std::istream. |
149 | */ |
150 | BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, linear_feedback_shift_engine, x) |
151 | { |
152 | is >> x.value; |
153 | return is; |
154 | } |
155 | |
156 | /** |
157 | * Returns true if the two generators will produce identical |
158 | * sequences of outputs. |
159 | */ |
160 | BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(linear_feedback_shift_engine, x, y) |
161 | { return x.value == y.value; } |
162 | |
163 | /** |
164 | * Returns true if the two generators will produce different |
165 | * sequences of outputs. |
166 | */ |
167 | BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(linear_feedback_shift_engine) |
168 | |
169 | private: |
170 | /// \cond show_private |
171 | static UIntType wordmask() { return boost::low_bits_mask_t<w>::sig_bits; } |
172 | /// \endcond |
173 | UIntType value; |
174 | }; |
175 | |
176 | #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION |
177 | // A definition is required even for integral static constants |
178 | template<class UIntType, int w, int k, int q, int s> |
179 | const bool linear_feedback_shift_engine<UIntType, w, k, q, s>::has_fixed_range; |
180 | template<class UIntType, int w, int k, int q, int s> |
181 | const int linear_feedback_shift_engine<UIntType, w, k, q, s>::word_size; |
182 | template<class UIntType, int w, int k, int q, int s> |
183 | const int linear_feedback_shift_engine<UIntType, w, k, q, s>::exponent1; |
184 | template<class UIntType, int w, int k, int q, int s> |
185 | const int linear_feedback_shift_engine<UIntType, w, k, q, s>::exponent2; |
186 | template<class UIntType, int w, int k, int q, int s> |
187 | const int linear_feedback_shift_engine<UIntType, w, k, q, s>::step_size; |
188 | template<class UIntType, int w, int k, int q, int s> |
189 | const UIntType linear_feedback_shift_engine<UIntType, w, k, q, s>::default_seed; |
190 | #endif |
191 | |
192 | /// \cond show_deprecated |
193 | |
194 | /** Provided for backwards compatibility. */ |
195 | template<class UIntType, int w, int k, int q, int s, UIntType v = 0> |
196 | class linear_feedback_shift : |
197 | public linear_feedback_shift_engine<UIntType, w, k, q, s> |
198 | { |
199 | typedef linear_feedback_shift_engine<UIntType, w, k, q, s> base_type; |
200 | public: |
201 | linear_feedback_shift() {} |
202 | BOOST_RANDOM_DETAIL_SEED_SEQ_CONSTRUCTOR(linear_feedback_shift, |
203 | SeedSeq, seq) |
204 | { seed(seq); } |
205 | BOOST_RANDOM_DETAIL_ARITHMETIC_CONSTRUCTOR(linear_feedback_shift, |
206 | UIntType, val) |
207 | { seed(val); } |
208 | template<class It> |
209 | linear_feedback_shift(It& first, It last) : base_type(first, last) {} |
210 | }; |
211 | |
212 | /// \endcond |
213 | |
214 | } // namespace random |
215 | } // namespace boost |
216 | |
217 | #endif // BOOST_RANDOM_LINEAR_FEEDBACK_SHIFT_HPP |
218 | |