Chris@16: /* boost random/xor_combine.hpp header file
Chris@16:  *
Chris@16:  * Copyright Jens Maurer 2002
Chris@16:  * Distributed under the Boost Software License, Version 1.0. (See
Chris@16:  * accompanying file LICENSE_1_0.txt or copy at
Chris@16:  * http://www.boost.org/LICENSE_1_0.txt)
Chris@16:  *
Chris@16:  * See http://www.boost.org for most recent version including documentation.
Chris@16:  *
Chris@101:  * $Id$
Chris@16:  *
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_RANDOM_XOR_COMBINE_HPP
Chris@16: #define BOOST_RANDOM_XOR_COMBINE_HPP
Chris@16: 
Chris@16: #include <istream>
Chris@16: #include <iosfwd>
Chris@16: #include <cassert>
Chris@16: #include <algorithm> // for std::min and std::max
Chris@16: #include <boost/config.hpp>
Chris@16: #include <boost/limits.hpp>
Chris@16: #include <boost/cstdint.hpp>     // uint32_t
Chris@16: #include <boost/random/detail/config.hpp>
Chris@16: #include <boost/random/detail/seed.hpp>
Chris@16: #include <boost/random/detail/seed_impl.hpp>
Chris@101: #include <boost/random/detail/operators.hpp>
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace random {
Chris@16: 
Chris@16: /**
Chris@16:  * Instantiations of @c xor_combine_engine model a
Chris@16:  * \pseudo_random_number_generator.  To produce its output it
Chris@16:  * invokes each of the base generators, shifts their results
Chris@16:  * and xors them together.
Chris@16:  */
Chris@16: template<class URNG1, int s1, class URNG2, int s2>
Chris@16: class xor_combine_engine
Chris@16: {
Chris@16: public:
Chris@16:     typedef URNG1 base1_type;
Chris@16:     typedef URNG2 base2_type;
Chris@16:     typedef typename base1_type::result_type result_type;
Chris@16: 
Chris@16:     BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
Chris@16:     BOOST_STATIC_CONSTANT(int, shift1 = s1);
Chris@16:     BOOST_STATIC_CONSTANT(int, shift2 = s2);
Chris@16: 
Chris@16:     /**
Chris@16:      * Constructors a @c xor_combine_engine by default constructing
Chris@16:      * both base generators.
Chris@16:      */
Chris@16:     xor_combine_engine() : _rng1(), _rng2() { }
Chris@16: 
Chris@16:     /** Constructs a @c xor_combine by copying two base generators. */
Chris@16:     xor_combine_engine(const base1_type & rng1, const base2_type & rng2)
Chris@16:       : _rng1(rng1), _rng2(rng2) { }
Chris@16: 
Chris@16:     /**
Chris@16:      * Constructs a @c xor_combine_engine, seeding both base generators
Chris@16:      * with @c v.
Chris@16:      *
Chris@16:      * @xmlwarning
Chris@16:      * The exact algorithm used by this function may change in the future.
Chris@16:      * @endxmlwarning
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_ARITHMETIC_CONSTRUCTOR(xor_combine_engine,
Chris@16:         result_type, v)
Chris@16:     { seed(v); }
Chris@16: 
Chris@16:     /**
Chris@16:      * Constructs a @c xor_combine_engine, seeding both base generators
Chris@16:      * with values produced by @c seq.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_SEED_SEQ_CONSTRUCTOR(xor_combine_engine,
Chris@16:         SeedSeq, seq)
Chris@16:     { seed(seq); }
Chris@16: 
Chris@16:     /**
Chris@16:      * Constructs a @c xor_combine_engine, seeding both base generators
Chris@16:      * with values from the iterator range [first, last) and changes
Chris@16:      * first to point to the element after the last one used.  If there
Chris@16:      * are not enough elements in the range to seed both generators,
Chris@16:      * throws @c std::invalid_argument.
Chris@16:      */
Chris@16:     template<class It> xor_combine_engine(It& first, It last)
Chris@16:       : _rng1(first, last), _rng2( /* advanced by other call */ first, last) { }
Chris@16: 
Chris@16:     /** Calls @c seed() for both base generators. */
Chris@16:     void seed() { _rng1.seed(); _rng2.seed(); }
Chris@16: 
Chris@16:     /** @c seeds both base generators with @c v. */
Chris@16:     BOOST_RANDOM_DETAIL_ARITHMETIC_SEED(xor_combine_engine, result_type, v)
Chris@16:     { _rng1.seed(v); _rng2.seed(v); }
Chris@16: 
Chris@16:     /** @c seeds both base generators with values produced by @c seq. */
Chris@16:     BOOST_RANDOM_DETAIL_SEED_SEQ_SEED(xor_combine_engine, SeedSeq, seq)
Chris@16:     { _rng1.seed(seq); _rng2.seed(seq); }
Chris@16: 
Chris@16:     /**
Chris@16:      * seeds both base generators with values from the iterator
Chris@16:      * range [first, last) and changes first to point to the element
Chris@16:      * after the last one used.  If there are not enough elements in
Chris@16:      * the range to seed both generators, throws @c std::invalid_argument.
Chris@16:      */
Chris@16:     template<class It> void seed(It& first, It last)
Chris@16:     {
Chris@16:         _rng1.seed(first, last);
Chris@16:         _rng2.seed(first, last);
Chris@16:     }
Chris@16: 
Chris@16:     /** Returns the first base generator. */
Chris@16:     const base1_type& base1() const { return _rng1; }
Chris@16: 
Chris@16:     /** Returns the second base generator. */
Chris@16:     const base2_type& base2() const { return _rng2; }
Chris@16: 
Chris@16:     /** Returns the next value of the generator. */
Chris@16:     result_type operator()()
Chris@16:     {
Chris@16:         return (_rng1() << s1) ^ (_rng2() << s2);
Chris@16:     }
Chris@16:   
Chris@16:     /** Fills a range with random values */
Chris@16:     template<class Iter>
Chris@16:     void generate(Iter first, Iter last)
Chris@16:     { detail::generate_from_int(*this, first, last); }
Chris@16: 
Chris@16:     /** Advances the state of the generator by @c z. */
Chris@16:     void discard(boost::uintmax_t z)
Chris@16:     {
Chris@16:         _rng1.discard(z);
Chris@16:         _rng2.discard(z);
Chris@16:     }
Chris@16: 
Chris@16:     /** Returns the smallest value that the generator can produce. */
Chris@16:     static result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () { return (std::min)((URNG1::min)(), (URNG2::min)()); }
Chris@16:     /** Returns the largest value that the generator can produce. */
Chris@16:     static result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () { return (std::max)((URNG1::min)(), (URNG2::max)()); }
Chris@16: 
Chris@16:     /**
Chris@16:      * Writes the textual representation of the generator to a @c std::ostream.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, xor_combine_engine, s)
Chris@16:     {
Chris@16:         os << s._rng1 << ' ' << s._rng2;
Chris@16:         return os;
Chris@16:     }
Chris@16:     
Chris@16:     /**
Chris@16:      * Reads the textual representation of the generator from a @c std::istream.
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, xor_combine_engine, s)
Chris@16:     {
Chris@16:         is >> s._rng1 >> std::ws >> s._rng2;
Chris@16:         return is;
Chris@16:     }
Chris@16:     
Chris@16:     /** Returns true if the two generators will produce identical sequences. */
Chris@16:     BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(xor_combine_engine, x, y)
Chris@16:     { return x._rng1 == y._rng1 && x._rng2 == y._rng2; }
Chris@16:     
Chris@16:     /** Returns true if the two generators will produce different sequences. */
Chris@16:     BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(xor_combine_engine)
Chris@16: 
Chris@16: private:
Chris@16:     base1_type _rng1;
Chris@16:     base2_type _rng2;
Chris@16: };
Chris@16: 
Chris@16: #ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
Chris@16: //  A definition is required even for integral static constants
Chris@16: template<class URNG1, int s1, class URNG2, int s2>
Chris@16: const bool xor_combine_engine<URNG1, s1, URNG2, s2>::has_fixed_range;
Chris@16: template<class URNG1, int s1, class URNG2, int s2>
Chris@16: const int xor_combine_engine<URNG1, s1, URNG2, s2>::shift1;
Chris@16: template<class URNG1, int s1, class URNG2, int s2>
Chris@16: const int xor_combine_engine<URNG1, s1, URNG2, s2>::shift2;
Chris@16: #endif
Chris@16: 
Chris@16: /// \cond show_private
Chris@16: 
Chris@16: /** Provided for backwards compatibility. */
Chris@16: template<class URNG1, int s1, class URNG2, int s2,
Chris@16:     typename URNG1::result_type v = 0>
Chris@16: class xor_combine : public xor_combine_engine<URNG1, s1, URNG2, s2>
Chris@16: {
Chris@16:     typedef xor_combine_engine<URNG1, s1, URNG2, s2> base_type;
Chris@16: public:
Chris@16:     typedef typename base_type::result_type result_type;
Chris@16:     xor_combine() {}
Chris@16:     xor_combine(result_type val) : base_type(val) {}
Chris@16:     template<class It>
Chris@16:     xor_combine(It& first, It last) : base_type(first, last) {}
Chris@16:     xor_combine(const URNG1 & rng1, const URNG2 & rng2)
Chris@16:       : base_type(rng1, rng2) { }
Chris@16: 
Chris@16:     result_type min BOOST_PREVENT_MACRO_SUBSTITUTION () const { return (std::min)((this->base1().min)(), (this->base2().min)()); }
Chris@16:     result_type max BOOST_PREVENT_MACRO_SUBSTITUTION () const { return (std::max)((this->base1().min)(), (this->base2().max)()); }
Chris@16: };
Chris@16: 
Chris@16: /// \endcond
Chris@16: 
Chris@16: } // namespace random
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #endif // BOOST_RANDOM_XOR_COMBINE_HPP