235 lines
7.3 KiB
C++
235 lines
7.3 KiB
C++
/* 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 60755 2010-03-22 00:45:06Z 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 <iostream>
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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/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 \additive_combine model a
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* \pseudo_random_number_generator. It combines two multiplicative
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* \linear_congruential 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 number generators, each with c = 0. Each invocation
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* returns a random number X(n) := (MLCG1(n) - MLCG2(n)) mod (m1 - 1), where
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* m1 denotes the modulus of MLCG1.
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*
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* The template parameter @c val is the validation value checked by validation.
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*/
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template<class MLCG1, class MLCG2,
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#ifndef BOOST_NO_DEPENDENT_TYPES_IN_TEMPLATE_VALUE_PARAMETERS
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typename MLCG1::result_type
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#else
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int32_t
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#endif
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val>
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class additive_combine
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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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#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
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static const bool has_fixed_range = true;
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static const result_type min_value = 1;
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static const result_type max_value = MLCG1::max_value-1;
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#else
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enum { has_fixed_range = false };
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#endif
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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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result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { 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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result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return (_mlcg1.max)()-1; }
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/**
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* Constructs an \additive_combine generator using the
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* default constructors of the two base generators.
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*/
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additive_combine() : _mlcg1(), _mlcg2() { }
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/**
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* Constructs an \additive_combine generator, using aseed as
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* the constructor argument for both base generators.
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*/
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explicit additive_combine(result_type aseed)
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: _mlcg1(aseed), _mlcg2(aseed) { }
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/**
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* Constructs an \additive_combine generator, 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(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 \additive_combine generator 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(It& first, It last)
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: _mlcg1(first, last), _mlcg2(first, last) { }
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/**
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* Seeds an \additive_combine generator 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 \additive_combine generator, using @c aseed as the
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* seed for both base generators.
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*/
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void seed(result_type aseed)
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{
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_mlcg1.seed(aseed);
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_mlcg2.seed(aseed);
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}
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/**
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* Seeds an \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 \additive_combine generator 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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/**
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* Returns: the next value of the generator
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*/
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result_type operator()() {
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result_type z = _mlcg1() - _mlcg2();
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if(z < 1)
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z += MLCG1::modulus-1;
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return z;
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}
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static bool validation(result_type x) { return val == x; }
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#ifndef BOOST_NO_OPERATORS_IN_NAMESPACE
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#ifndef BOOST_RANDOM_NO_STREAM_OPERATORS
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/**
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* Writes the state of an \additive_combine generator to a @c
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* std::ostream. The textual representation of an \additive_combine
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* generator is the textual representation of the first base
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* generator followed by the textual representation of the
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* second base generator.
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*/
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template<class CharT, class Traits>
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friend std::basic_ostream<CharT,Traits>&
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operator<<(std::basic_ostream<CharT,Traits>& os, const additive_combine& 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 \additive_combine generator from a
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* @c std::istream.
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*/
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template<class CharT, class Traits>
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friend std::basic_istream<CharT,Traits>&
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operator>>(std::basic_istream<CharT,Traits>& is, additive_combine& r)
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{ is >> r._mlcg1 >> std::ws >> r._mlcg2; return is; }
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#endif
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/**
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* Returns: true iff the two \additive_combine generators will
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* produce the same sequence of values.
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*/
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friend bool operator==(const additive_combine& x, const additive_combine& 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 \additive_combine generators will
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* produce different sequences of values.
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*/
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friend bool operator!=(const additive_combine& x, const additive_combine& y)
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{ return !(x == y); }
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#else
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// Use a member function; Streamable concept not supported.
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bool operator==(const additive_combine& rhs) const
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{ return _mlcg1 == rhs._mlcg1 && _mlcg2 == rhs._mlcg2; }
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bool operator!=(const additive_combine& rhs) const
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{ return !(*this == rhs); }
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#endif
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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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} // namespace random
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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 random::additive_combine<
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random::linear_congruential<int32_t, 40014, 0, 2147483563, 0>,
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random::linear_congruential<int32_t, 40692, 0, 2147483399, 0>,
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2060321752> ecuyer1988;
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} // namespace boost
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#endif // BOOST_RANDOM_ADDITIVE_COMBINE_HPP
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