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283 lines
8.7 KiB
283 lines
8.7 KiB
/* boost random/additive_combine.hpp header file |
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* |
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* Copyright Jens Maurer 2000-2001 |
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* Distributed under the Boost Software License, Version 1.0. (See |
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* accompanying file LICENSE_1_0.txt or copy at |
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* http://www.boost.org/LICENSE_1_0.txt) |
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* |
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* See http://www.boost.org for most recent version including documentation. |
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* |
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* $Id: additive_combine.hpp 71018 2011-04-05 21:27:52Z steven_watanabe $ |
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* |
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* Revision history |
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* 2001-02-18 moved to individual header files |
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*/ |
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#ifndef BOOST_RANDOM_ADDITIVE_COMBINE_HPP |
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#define BOOST_RANDOM_ADDITIVE_COMBINE_HPP |
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#include <istream> |
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#include <iosfwd> |
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#include <algorithm> // for std::min and std::max |
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#include <boost/config.hpp> |
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#include <boost/cstdint.hpp> |
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#include <boost/random/detail/config.hpp> |
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#include <boost/random/detail/operators.hpp> |
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#include <boost/random/detail/seed.hpp> |
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#include <boost/random/linear_congruential.hpp> |
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namespace boost { |
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namespace random { |
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/** |
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* An instantiation of class template @c additive_combine_engine models a |
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* \pseudo_random_number_generator. It combines two multiplicative |
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* \linear_congruential_engine number generators, i.e. those with @c c = 0. |
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* It is described in |
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* |
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* @blockquote |
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* "Efficient and Portable Combined Random Number Generators", Pierre L'Ecuyer, |
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* Communications of the ACM, Vol. 31, No. 6, June 1988, pp. 742-749, 774 |
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* @endblockquote |
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* |
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* The template parameters MLCG1 and MLCG2 shall denote two different |
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* \linear_congruential_engine number generators, each with c = 0. Each |
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* invocation returns a random number |
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* X(n) := (MLCG1(n) - MLCG2(n)) mod (m1 - 1), |
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* where m1 denotes the modulus of MLCG1. |
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*/ |
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template<class MLCG1, class MLCG2> |
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class additive_combine_engine |
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{ |
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public: |
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typedef MLCG1 first_base; |
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typedef MLCG2 second_base; |
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typedef typename MLCG1::result_type result_type; |
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// Required by old Boost.Random concept |
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BOOST_STATIC_CONSTANT(bool, has_fixed_range = false); |
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/** |
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* Returns the smallest value that the generator can produce |
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*/ |
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static result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () |
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{ return 1; } |
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/** |
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* Returns the largest value that the generator can produce |
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*/ |
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static result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () |
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{ return MLCG1::modulus-1; } |
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/** |
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* Constructs an @c additive_combine_engine using the |
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* default constructors of the two base generators. |
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*/ |
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additive_combine_engine() : _mlcg1(), _mlcg2() { } |
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/** |
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* Constructs an @c additive_combine_engine, using seed as |
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* the constructor argument for both base generators. |
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*/ |
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BOOST_RANDOM_DETAIL_ARITHMETIC_CONSTRUCTOR(additive_combine_engine, |
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result_type, seed_arg) |
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{ |
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_mlcg1.seed(seed_arg); |
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_mlcg2.seed(seed_arg); |
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} |
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/** |
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* Constructs an @c additive_combine_engine, using seq as |
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* the constructor argument for both base generators. |
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* |
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* @xmlwarning |
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* The semantics of this function are liable to change. |
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* A @c seed_seq is designed to generate all the seeds |
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* in one shot, but this seeds the two base engines |
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* independantly and probably ends up giving the same |
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* sequence to both. |
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* @endxmlwarning |
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*/ |
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BOOST_RANDOM_DETAIL_SEED_SEQ_CONSTRUCTOR(additive_combine_engine, |
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SeedSeq, seq) |
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{ |
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_mlcg1.seed(seq); |
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_mlcg2.seed(seq); |
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} |
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/** |
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* Constructs an @c additive_combine_engine, using |
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* @c seed1 and @c seed2 as the constructor argument to |
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* the first and second base generators, respectively. |
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*/ |
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additive_combine_engine(typename MLCG1::result_type seed1, |
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typename MLCG2::result_type seed2) |
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: _mlcg1(seed1), _mlcg2(seed2) { } |
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/** |
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* Contructs an @c additive_combine_engine with |
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* values from the range defined by the input iterators first |
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* and last. first will be modified to point to the element |
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* after the last one used. |
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* |
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* Throws: @c std::invalid_argument if the input range is too small. |
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* |
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* Exception Safety: Basic |
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*/ |
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template<class It> additive_combine_engine(It& first, It last) |
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: _mlcg1(first, last), _mlcg2(first, last) { } |
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/** |
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* Seeds an @c additive_combine_engine using the default |
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* seeds of the two base generators. |
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*/ |
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void seed() |
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{ |
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_mlcg1.seed(); |
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_mlcg2.seed(); |
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} |
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/** |
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* Seeds an @c additive_combine_engine, using @c seed as the |
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* seed for both base generators. |
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*/ |
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BOOST_RANDOM_DETAIL_ARITHMETIC_SEED(additive_combine_engine, |
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result_type, seed_arg) |
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{ |
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_mlcg1.seed(seed_arg); |
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_mlcg2.seed(seed_arg); |
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} |
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/** |
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* Seeds an @c additive_combine_engine, using @c seq to |
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* seed both base generators. |
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* |
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* See the warning on the corresponding constructor. |
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*/ |
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BOOST_RANDOM_DETAIL_SEED_SEQ_SEED(additive_combine_engine, |
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SeedSeq, seq) |
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{ |
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_mlcg1.seed(seq); |
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_mlcg2.seed(seq); |
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} |
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/** |
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* Seeds an @c additive_combine generator, using @c seed1 and @c seed2 as |
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* the seeds to the first and second base generators, respectively. |
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*/ |
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void seed(typename MLCG1::result_type seed1, |
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typename MLCG2::result_type seed2) |
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{ |
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_mlcg1.seed(seed1); |
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_mlcg2.seed(seed2); |
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} |
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/** |
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* Seeds an @c additive_combine_engine with |
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* values from the range defined by the input iterators first |
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* and last. first will be modified to point to the element |
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* after the last one used. |
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* |
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* Throws: @c std::invalid_argument if the input range is too small. |
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* |
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* Exception Safety: Basic |
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*/ |
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template<class It> void seed(It& first, It last) |
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{ |
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_mlcg1.seed(first, last); |
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_mlcg2.seed(first, last); |
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} |
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/** Returns the next value of the generator. */ |
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result_type operator()() { |
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result_type val1 = _mlcg1(); |
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result_type val2 = _mlcg2(); |
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if(val2 < val1) return val1 - val2; |
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else return val1 - val2 + MLCG1::modulus - 1; |
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} |
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/** Fills a range with random values */ |
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template<class Iter> |
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void generate(Iter first, Iter last) |
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{ detail::generate_from_int(*this, first, last); } |
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/** Advances the state of the generator by @c z. */ |
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void discard(boost::uintmax_t z) |
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{ |
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_mlcg1.discard(z); |
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_mlcg2.discard(z); |
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} |
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/** |
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* Writes the state of an @c additive_combine_engine to a @c |
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* std::ostream. The textual representation of an @c |
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* additive_combine_engine is the textual representation of |
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* the first base generator followed by the textual representation |
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* of the second base generator. |
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*/ |
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BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, additive_combine_engine, r) |
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{ os << r._mlcg1 << ' ' << r._mlcg2; return os; } |
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/** |
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* Reads the state of an @c additive_combine_engine from a |
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* @c std::istream. |
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*/ |
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BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, additive_combine_engine, r) |
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{ is >> r._mlcg1 >> std::ws >> r._mlcg2; return is; } |
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/** |
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* Returns: true iff the two @c additive_combine_engines will |
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* produce the same sequence of values. |
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*/ |
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BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(additive_combine_engine, x, y) |
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{ return x._mlcg1 == y._mlcg1 && x._mlcg2 == y._mlcg2; } |
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/** |
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* Returns: true iff the two @c additive_combine_engines will |
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* produce different sequences of values. |
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*/ |
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BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(additive_combine_engine) |
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private: |
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MLCG1 _mlcg1; |
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MLCG2 _mlcg2; |
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}; |
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#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION |
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template<class MLCG1, class MLCG2> |
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const bool additive_combine_engine<MLCG1, MLCG2>::has_fixed_range; |
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#endif |
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/// \cond show_deprecated |
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/** Provided for backwards compatibility. */ |
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template<class MLCG1, class MLCG2, typename MLCG1::result_type val = 0> |
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class additive_combine : public additive_combine_engine<MLCG1, MLCG2> |
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{ |
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typedef additive_combine_engine<MLCG1, MLCG2> base_t; |
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public: |
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typedef typename base_t::result_type result_type; |
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additive_combine() {} |
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template<class T> |
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additive_combine(T& arg) : base_t(arg) {} |
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template<class T> |
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additive_combine(const T& arg) : base_t(arg) {} |
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template<class It> |
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additive_combine(It& first, It last) : base_t(first, last) {} |
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}; |
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/// \endcond |
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/** |
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* The specialization \ecuyer1988 was suggested in |
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* |
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* @blockquote |
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* "Efficient and Portable Combined Random Number Generators", Pierre L'Ecuyer, |
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* Communications of the ACM, Vol. 31, No. 6, June 1988, pp. 742-749, 774 |
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* @endblockquote |
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*/ |
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typedef additive_combine_engine< |
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linear_congruential_engine<uint32_t, 40014, 0, 2147483563>, |
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linear_congruential_engine<uint32_t, 40692, 0, 2147483399> |
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> ecuyer1988; |
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} // namespace random |
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using random::ecuyer1988; |
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} // namespace boost |
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#endif // BOOST_RANDOM_ADDITIVE_COMBINE_HPP
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