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/Src/Dependencies/Boost/boost/random/additive_combine.hpp

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  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: additive_combine.hpp 71018 2011-04-05 21:27:52Z steven_watanabe $
 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
 29namespace boost {
 30namespace 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 */
 49template<class MLCG1, class MLCG2>
 50class additive_combine_engine
 51{
 52public:
 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
234private:
235    MLCG1 _mlcg1;
236    MLCG2 _mlcg2;
237};
238
239#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
240template<class MLCG1, class MLCG2>
241const bool additive_combine_engine<MLCG1, MLCG2>::has_fixed_range;
242#endif
243
244/// \cond show_deprecated
245
246/** Provided for backwards compatibility. */
247template<class MLCG1, class MLCG2, typename MLCG1::result_type val = 0>
248class additive_combine : public additive_combine_engine<MLCG1, MLCG2>
249{
250    typedef additive_combine_engine<MLCG1, MLCG2> base_t;
251public:
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 */
272typedef 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
279using random::ecuyer1988;
280
281} // namespace boost
282
283#endif // BOOST_RANDOM_ADDITIVE_COMBINE_HPP