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