284 lines
8.9 KiB
Plaintext
284 lines
8.9 KiB
Plaintext
/* 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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* $Id$
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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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