1 | /* boost random/detail/seed.hpp header file |
2 | * |
3 | * Copyright Steven Watanabe 2009 |
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 | #ifndef BOOST_RANDOM_DETAIL_SEED_IMPL_HPP |
14 | #define BOOST_RANDOM_DETAIL_SEED_IMPL_HPP |
15 | |
16 | #include <stdexcept> |
17 | #include <boost/cstdint.hpp> |
18 | #include <boost/throw_exception.hpp> |
19 | #include <boost/config/no_tr1/cmath.hpp> |
20 | #include <boost/integer/integer_mask.hpp> |
21 | #include <boost/integer/static_log2.hpp> |
22 | #include <boost/random/traits.hpp> |
23 | #include <boost/mpl/bool.hpp> |
24 | #include <boost/mpl/if.hpp> |
25 | #include <boost/mpl/int.hpp> |
26 | #include <boost/random/detail/const_mod.hpp> |
27 | #include <boost/random/detail/integer_log2.hpp> |
28 | #include <boost/random/detail/signed_unsigned_tools.hpp> |
29 | #include <boost/random/detail/generator_bits.hpp> |
30 | |
31 | #include <boost/random/detail/disable_warnings.hpp> |
32 | |
33 | namespace boost { |
34 | namespace random { |
35 | namespace detail { |
36 | |
37 | // finds the seed type of an engine, given its |
38 | // result_type. If the result_type is integral |
39 | // the seed type is the same. If the result_type |
40 | // is floating point, the seed type is uint32_t |
41 | template<class T> |
42 | struct seed_type |
43 | { |
44 | typedef typename boost::mpl::if_<boost::is_integral<T>, |
45 | T, |
46 | boost::uint32_t |
47 | >::type type; |
48 | }; |
49 | |
50 | template<int N> |
51 | struct const_pow_impl |
52 | { |
53 | template<class T> |
54 | static T call(T arg, int n, T result) |
55 | { |
56 | return const_pow_impl<N / 2>::call(T(arg * arg), n / 2, |
57 | n%2 == 0? result : T(result * arg)); |
58 | } |
59 | }; |
60 | |
61 | template<> |
62 | struct const_pow_impl<0> |
63 | { |
64 | template<class T> |
65 | static T call(T, int, T result) |
66 | { |
67 | return result; |
68 | } |
69 | }; |
70 | |
71 | // requires N is an upper bound on n |
72 | template<int N, class T> |
73 | inline T const_pow(T arg, int n) { return const_pow_impl<N>::call(arg, n, T(1)); } |
74 | |
75 | template<class T> |
76 | inline T pow2(int n) |
77 | { |
78 | typedef unsigned int_type; |
79 | const int max_bits = std::numeric_limits<int_type>::digits; |
80 | T multiplier = T(int_type(1) << (max_bits - 1)) * 2; |
81 | return (int_type(1) << (n % max_bits)) * |
82 | const_pow<std::numeric_limits<T>::digits / max_bits>(multiplier, n / max_bits); |
83 | } |
84 | |
85 | template<class Engine, class Iter> |
86 | void generate_from_real(Engine& eng, Iter begin, Iter end) |
87 | { |
88 | using std::fmod; |
89 | typedef typename Engine::result_type RealType; |
90 | const int Bits = detail::generator_bits<Engine>::value(); |
91 | int remaining_bits = 0; |
92 | boost::uint_least32_t saved_bits = 0; |
93 | RealType multiplier = pow2<RealType>( Bits); |
94 | RealType mult32 = RealType(4294967296.0); // 2^32 |
95 | while(true) { |
96 | RealType val = eng() * multiplier; |
97 | int available_bits = Bits; |
98 | // Make sure the compiler can optimize this out |
99 | // if it isn't possible. |
100 | if(Bits < 32 && available_bits < 32 - remaining_bits) { |
101 | saved_bits |= boost::uint_least32_t(val) << remaining_bits; |
102 | remaining_bits += Bits; |
103 | } else { |
104 | // If Bits < 32, then remaining_bits != 0, since |
105 | // if remaining_bits == 0, available_bits < 32 - 0, |
106 | // and we won't get here to begin with. |
107 | if(Bits < 32 || remaining_bits != 0) { |
108 | boost::uint_least32_t divisor = |
109 | (boost::uint_least32_t(1) << (32 - remaining_bits)); |
110 | boost::uint_least32_t = boost::uint_least32_t(fmod(val, mult32)) & (divisor - 1); |
111 | val = val / divisor; |
112 | *begin++ = saved_bits | (extra_bits << remaining_bits); |
113 | if(begin == end) return; |
114 | available_bits -= 32 - remaining_bits; |
115 | remaining_bits = 0; |
116 | } |
117 | // If Bits < 32 we should never enter this loop |
118 | if(Bits >= 32) { |
119 | for(; available_bits >= 32; available_bits -= 32) { |
120 | boost::uint_least32_t word = boost::uint_least32_t(fmod(val, mult32)); |
121 | val /= mult32; |
122 | *begin++ = word; |
123 | if(begin == end) return; |
124 | } |
125 | } |
126 | remaining_bits = available_bits; |
127 | saved_bits = static_cast<boost::uint_least32_t>(val); |
128 | } |
129 | } |
130 | } |
131 | |
132 | template<class Engine, class Iter> |
133 | void generate_from_int(Engine& eng, Iter begin, Iter end) |
134 | { |
135 | typedef typename Engine::result_type IntType; |
136 | typedef typename boost::random::traits::make_unsigned<IntType>::type unsigned_type; |
137 | int remaining_bits = 0; |
138 | boost::uint_least32_t saved_bits = 0; |
139 | unsigned_type range = boost::random::detail::subtract<IntType>()((eng.max)(), (eng.min)()); |
140 | |
141 | int bits = |
142 | (range == (std::numeric_limits<unsigned_type>::max)()) ? |
143 | std::numeric_limits<unsigned_type>::digits : |
144 | detail::integer_log2(range + 1); |
145 | |
146 | { |
147 | int discarded_bits = detail::integer_log2(bits); |
148 | unsigned_type excess = (range + 1) >> (bits - discarded_bits); |
149 | if(excess != 0) { |
150 | int = detail::integer_log2((excess - 1) ^ excess); |
151 | bits = bits - discarded_bits + extra_bits; |
152 | } |
153 | } |
154 | |
155 | unsigned_type mask = (static_cast<unsigned_type>(2) << (bits - 1)) - 1; |
156 | unsigned_type limit = ((range + 1) & ~mask) - 1; |
157 | |
158 | while(true) { |
159 | unsigned_type val; |
160 | do { |
161 | val = boost::random::detail::subtract<IntType>()(eng(), (eng.min)()); |
162 | } while(limit != range && val > limit); |
163 | val &= mask; |
164 | int available_bits = bits; |
165 | if(available_bits == 32) { |
166 | *begin++ = static_cast<boost::uint_least32_t>(val) & 0xFFFFFFFFu; |
167 | if(begin == end) return; |
168 | } else if(available_bits % 32 == 0) { |
169 | for(int i = 0; i < available_bits / 32; ++i) { |
170 | boost::uint_least32_t word = boost::uint_least32_t(val) & 0xFFFFFFFFu; |
171 | int suppress_warning = (bits >= 32); |
172 | BOOST_ASSERT(suppress_warning == 1); |
173 | val >>= (32 * suppress_warning); |
174 | *begin++ = word; |
175 | if(begin == end) return; |
176 | } |
177 | } else if(bits < 32 && available_bits < 32 - remaining_bits) { |
178 | saved_bits |= boost::uint_least32_t(val) << remaining_bits; |
179 | remaining_bits += bits; |
180 | } else { |
181 | if(bits < 32 || remaining_bits != 0) { |
182 | boost::uint_least32_t = boost::uint_least32_t(val) & ((boost::uint_least32_t(1) << (32 - remaining_bits)) - 1); |
183 | val >>= 32 - remaining_bits; |
184 | *begin++ = saved_bits | (extra_bits << remaining_bits); |
185 | if(begin == end) return; |
186 | available_bits -= 32 - remaining_bits; |
187 | remaining_bits = 0; |
188 | } |
189 | if(bits >= 32) { |
190 | for(; available_bits >= 32; available_bits -= 32) { |
191 | boost::uint_least32_t word = boost::uint_least32_t(val) & 0xFFFFFFFFu; |
192 | int suppress_warning = (bits >= 32); |
193 | BOOST_ASSERT(suppress_warning == 1); |
194 | val >>= (32 * suppress_warning); |
195 | *begin++ = word; |
196 | if(begin == end) return; |
197 | } |
198 | } |
199 | remaining_bits = available_bits; |
200 | saved_bits = static_cast<boost::uint_least32_t>(val); |
201 | } |
202 | } |
203 | } |
204 | |
205 | template<class Engine, class Iter> |
206 | void generate_impl(Engine& eng, Iter first, Iter last, boost::mpl::true_) |
207 | { |
208 | return detail::generate_from_int(eng, first, last); |
209 | } |
210 | |
211 | template<class Engine, class Iter> |
212 | void generate_impl(Engine& eng, Iter first, Iter last, boost::mpl::false_) |
213 | { |
214 | return detail::generate_from_real(eng, first, last); |
215 | } |
216 | |
217 | template<class Engine, class Iter> |
218 | void generate(Engine& eng, Iter first, Iter last) |
219 | { |
220 | return detail::generate_impl(eng, first, last, boost::random::traits::is_integral<typename Engine::result_type>()); |
221 | } |
222 | |
223 | |
224 | |
225 | template<class IntType, IntType m, class SeedSeq> |
226 | IntType seed_one_int(SeedSeq& seq) |
227 | { |
228 | static const int log = ::boost::mpl::if_c<(m == 0), |
229 | ::boost::mpl::int_<(::std::numeric_limits<IntType>::digits)>, |
230 | ::boost::static_log2<m> >::type::value; |
231 | static const int k = |
232 | (log + ((~(static_cast<IntType>(2) << (log - 1)) & m)? 32 : 31)) / 32; |
233 | ::boost::uint_least32_t array[log / 32 + 4]; |
234 | seq.generate(&array[0], &array[0] + k + 3); |
235 | IntType s = 0; |
236 | for(int j = 0; j < k; ++j) { |
237 | IntType digit = const_mod<IntType, m>::apply(IntType(array[j+3])); |
238 | IntType mult = IntType(1) << 32*j; |
239 | s = const_mod<IntType, m>::mult_add(mult, digit, s); |
240 | } |
241 | return s; |
242 | } |
243 | |
244 | template<class IntType, IntType m, class Iter> |
245 | IntType get_one_int(Iter& first, Iter last) |
246 | { |
247 | static const int log = ::boost::mpl::if_c<(m == 0), |
248 | ::boost::mpl::int_<(::std::numeric_limits<IntType>::digits)>, |
249 | ::boost::static_log2<m> >::type::value; |
250 | static const int k = |
251 | (log + ((~(static_cast<IntType>(2) << (log - 1)) & m)? 32 : 31)) / 32; |
252 | IntType s = 0; |
253 | for(int j = 0; j < k; ++j) { |
254 | if(first == last) { |
255 | boost::throw_exception(::std::invalid_argument("Not enough elements in call to seed." )); |
256 | } |
257 | IntType digit = const_mod<IntType, m>::apply(IntType(*first++)); |
258 | IntType mult = IntType(1) << 32*j; |
259 | s = const_mod<IntType, m>::mult_add(mult, digit, s); |
260 | } |
261 | return s; |
262 | } |
263 | |
264 | // TODO: work in-place whenever possible |
265 | template<int w, std::size_t n, class SeedSeq, class UIntType> |
266 | void seed_array_int_impl(SeedSeq& seq, UIntType (&x)[n]) |
267 | { |
268 | boost::uint_least32_t storage[((w+31)/32) * n]; |
269 | seq.generate(&storage[0], &storage[0] + ((w+31)/32) * n); |
270 | for(std::size_t j = 0; j < n; j++) { |
271 | UIntType val = 0; |
272 | for(std::size_t k = 0; k < (w+31)/32; ++k) { |
273 | val += static_cast<UIntType>(storage[(w+31)/32*j + k]) << 32*k; |
274 | } |
275 | x[j] = val & ::boost::low_bits_mask_t<w>::sig_bits; |
276 | } |
277 | } |
278 | |
279 | template<int w, std::size_t n, class SeedSeq, class IntType> |
280 | inline void seed_array_int_impl(SeedSeq& seq, IntType (&x)[n], boost::mpl::true_) |
281 | { |
282 | BOOST_STATIC_ASSERT_MSG(boost::is_integral<IntType>::value, "Sorry but this routine has not been ported to non built-in integers as it relies on a reinterpret_cast." ); |
283 | typedef typename boost::make_unsigned<IntType>::type unsigned_array[n]; |
284 | seed_array_int_impl<w>(seq, reinterpret_cast<unsigned_array&>(x)); |
285 | } |
286 | |
287 | template<int w, std::size_t n, class SeedSeq, class IntType> |
288 | inline void seed_array_int_impl(SeedSeq& seq, IntType (&x)[n], boost::mpl::false_) |
289 | { |
290 | seed_array_int_impl<w>(seq, x); |
291 | } |
292 | |
293 | template<int w, std::size_t n, class SeedSeq, class IntType> |
294 | inline void seed_array_int(SeedSeq& seq, IntType (&x)[n]) |
295 | { |
296 | seed_array_int_impl<w>(seq, x, boost::random::traits::is_signed<IntType>()); |
297 | } |
298 | |
299 | template<int w, std::size_t n, class Iter, class UIntType> |
300 | void fill_array_int_impl(Iter& first, Iter last, UIntType (&x)[n]) |
301 | { |
302 | for(std::size_t j = 0; j < n; j++) { |
303 | UIntType val = 0; |
304 | for(std::size_t k = 0; k < (w+31)/32; ++k) { |
305 | if(first == last) { |
306 | boost::throw_exception(std::invalid_argument("Not enough elements in call to seed." )); |
307 | } |
308 | val += static_cast<UIntType>(*first++) << 32*k; |
309 | } |
310 | x[j] = val & ::boost::low_bits_mask_t<w>::sig_bits; |
311 | } |
312 | } |
313 | |
314 | template<int w, std::size_t n, class Iter, class IntType> |
315 | inline void fill_array_int_impl(Iter& first, Iter last, IntType (&x)[n], boost::mpl::true_) |
316 | { |
317 | BOOST_STATIC_ASSERT_MSG(boost::is_integral<IntType>::value, "Sorry but this routine has not been ported to non built-in integers as it relies on a reinterpret_cast." ); |
318 | typedef typename boost::make_unsigned<IntType>::type unsigned_array[n]; |
319 | fill_array_int_impl<w>(first, last, reinterpret_cast<unsigned_array&>(x)); |
320 | } |
321 | |
322 | template<int w, std::size_t n, class Iter, class IntType> |
323 | inline void fill_array_int_impl(Iter& first, Iter last, IntType (&x)[n], boost::mpl::false_) |
324 | { |
325 | fill_array_int_impl<w>(first, last, x); |
326 | } |
327 | |
328 | template<int w, std::size_t n, class Iter, class IntType> |
329 | inline void fill_array_int(Iter& first, Iter last, IntType (&x)[n]) |
330 | { |
331 | fill_array_int_impl<w>(first, last, x, boost::random::traits::is_signed<IntType>()); |
332 | } |
333 | |
334 | template<int w, std::size_t n, class RealType> |
335 | void seed_array_real_impl(const boost::uint_least32_t* storage, RealType (&x)[n]) |
336 | { |
337 | boost::uint_least32_t mask = ~((~boost::uint_least32_t(0)) << (w%32)); |
338 | RealType two32 = 4294967296.0; |
339 | const RealType divisor = RealType(1)/detail::pow2<RealType>(w); |
340 | unsigned int j; |
341 | for(j = 0; j < n; ++j) { |
342 | RealType val = RealType(0); |
343 | RealType mult = divisor; |
344 | for(int k = 0; k < w/32; ++k) { |
345 | val += *storage++ * mult; |
346 | mult *= two32; |
347 | } |
348 | if(mask != 0) { |
349 | val += (*storage++ & mask) * mult; |
350 | } |
351 | BOOST_ASSERT(val >= 0); |
352 | BOOST_ASSERT(val < 1); |
353 | x[j] = val; |
354 | } |
355 | } |
356 | |
357 | template<int w, std::size_t n, class SeedSeq, class RealType> |
358 | void seed_array_real(SeedSeq& seq, RealType (&x)[n]) |
359 | { |
360 | using std::pow; |
361 | boost::uint_least32_t storage[((w+31)/32) * n]; |
362 | seq.generate(&storage[0], &storage[0] + ((w+31)/32) * n); |
363 | seed_array_real_impl<w>(storage, x); |
364 | } |
365 | |
366 | template<int w, std::size_t n, class Iter, class RealType> |
367 | void fill_array_real(Iter& first, Iter last, RealType (&x)[n]) |
368 | { |
369 | boost::uint_least32_t mask = ~((~boost::uint_least32_t(0)) << (w%32)); |
370 | RealType two32 = 4294967296.0; |
371 | const RealType divisor = RealType(1)/detail::pow2<RealType>(w); |
372 | unsigned int j; |
373 | for(j = 0; j < n; ++j) { |
374 | RealType val = RealType(0); |
375 | RealType mult = divisor; |
376 | for(int k = 0; k < w/32; ++k, ++first) { |
377 | if(first == last) boost::throw_exception(std::invalid_argument("Not enough elements in call to seed." )); |
378 | val += *first * mult; |
379 | mult *= two32; |
380 | } |
381 | if(mask != 0) { |
382 | if(first == last) boost::throw_exception(std::invalid_argument("Not enough elements in call to seed." )); |
383 | val += (*first & mask) * mult; |
384 | ++first; |
385 | } |
386 | BOOST_ASSERT(val >= 0); |
387 | BOOST_ASSERT(val < 1); |
388 | x[j] = val; |
389 | } |
390 | } |
391 | |
392 | } |
393 | } |
394 | } |
395 | |
396 | #include <boost/random/detail/enable_warnings.hpp> |
397 | |
398 | #endif |
399 | |