Chris@16: /* boost random/discard_block.hpp header file
Chris@16:  *
Chris@16:  * Copyright Jens Maurer 2002
Chris@16:  * Copyright Steven Watanabe 2010
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:  * Revision history
Chris@16:  *  2001-03-02  created
Chris@16:  */
Chris@16: 
Chris@16: #ifndef BOOST_RANDOM_DISCARD_BLOCK_HPP
Chris@16: #define BOOST_RANDOM_DISCARD_BLOCK_HPP
Chris@16: 
Chris@16: #include <iostream>
Chris@16: #include <boost/config.hpp>
Chris@16: #include <boost/cstdint.hpp>
Chris@16: #include <boost/limits.hpp>
Chris@16: #include <boost/static_assert.hpp>
Chris@16: #include <boost/random/detail/config.hpp>
Chris@16: #include <boost/random/detail/seed.hpp>
Chris@101: #include <boost/random/detail/seed_impl.hpp>
Chris@16: 
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace random {
Chris@16: 
Chris@16: /**
Chris@16:  * The class template \discard_block_engine is a model of
Chris@16:  * \pseudo_random_number_generator.  It modifies
Chris@16:  * another generator by discarding parts of its output.
Chris@16:  * Out of every block of @c p results, the first @c r
Chris@16:  * will be returned and the rest discarded.
Chris@16:  *
Chris@16:  * Requires: 0 < p <= r
Chris@16:  */
Chris@16: template<class UniformRandomNumberGenerator, std::size_t p, std::size_t r>
Chris@16: class discard_block_engine
Chris@16: {
Chris@16:     typedef typename detail::seed_type<
Chris@16:         typename UniformRandomNumberGenerator::result_type>::type seed_type;
Chris@16: public:
Chris@16:     typedef UniformRandomNumberGenerator base_type;
Chris@16:     typedef typename base_type::result_type result_type;
Chris@16: 
Chris@16:     BOOST_STATIC_CONSTANT(std::size_t, block_size = p);
Chris@16:     BOOST_STATIC_CONSTANT(std::size_t, used_block = r);
Chris@16: 
Chris@16:     BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
Chris@16:     BOOST_STATIC_CONSTANT(std::size_t, total_block = p);
Chris@16:     BOOST_STATIC_CONSTANT(std::size_t, returned_block = r);
Chris@16: 
Chris@16:     BOOST_STATIC_ASSERT(total_block >= returned_block);
Chris@16: 
Chris@16:     /** Uses the default seed for the base generator. */
Chris@16:     discard_block_engine() : _rng(), _n(0) { }
Chris@16:     /** Constructs a new \discard_block_engine with a copy of rng. */
Chris@16:     explicit discard_block_engine(const base_type & rng) : _rng(rng), _n(0) { }
Chris@16: 
Chris@101: #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
Chris@16:     /** Constructs a new \discard_block_engine with rng. */
Chris@16:     explicit discard_block_engine(base_type && rng) : _rng(rng), _n(0) { }
Chris@16: #endif
Chris@16: 
Chris@16:     /**
Chris@16:      * Creates a new \discard_block_engine and seeds the underlying
Chris@16:      * generator with @c value
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_ARITHMETIC_CONSTRUCTOR(discard_block_engine,
Chris@16:                                                seed_type, value)
Chris@16:     { _rng.seed(value); _n = 0; }
Chris@16:     
Chris@16:     /**
Chris@16:      * Creates a new \discard_block_engine and seeds the underlying
Chris@16:      * generator with @c seq
Chris@16:      */
Chris@16:     BOOST_RANDOM_DETAIL_SEED_SEQ_CONSTRUCTOR(discard_block_engine, SeedSeq, seq)
Chris@16:     { _rng.seed(seq); _n = 0; }
Chris@16:     
Chris@16:     /**
Chris@16:      * Creates a new \discard_block_engine and seeds the underlying
Chris@16:      * generator with first and last.
Chris@16:      */
Chris@16:     template<class It> discard_block_engine(It& first, It last)
Chris@16:       : _rng(first, last), _n(0) { }
Chris@16:     
Chris@16:     /** default seeds the underlying generator. */
Chris@16:     void seed() { _rng.seed(); _n = 0; }
Chris@16:     /** Seeds the underlying generator with s. */
Chris@16:     BOOST_RANDOM_DETAIL_ARITHMETIC_SEED(discard_block_engine, seed_type, s)
Chris@16:     { _rng.seed(s); _n = 0; }
Chris@16:     /** Seeds the underlying generator with seq. */
Chris@16:     BOOST_RANDOM_DETAIL_SEED_SEQ_SEED(discard_block_engine, SeedSeq, seq)
Chris@16:     { _rng.seed(seq); _n = 0; }
Chris@16:     /** Seeds the underlying generator with first and last. */
Chris@16:     template<class It> void seed(It& first, It last)
Chris@16:     { _rng.seed(first, last); _n = 0; }
Chris@16: 
Chris@16:     /** Returns the underlying engine. */
Chris@16:     const base_type& base() const { return _rng; }
Chris@16: 
Chris@16:     /** Returns the next value of the generator. */
Chris@16:     result_type operator()()
Chris@16:     {
Chris@16:         if(_n >= returned_block) {
Chris@16:             // discard values of random number generator
Chris@16:             // Don't use discard, since we still need to
Chris@16:             // be somewhat compatible with TR1.
Chris@16:             // _rng.discard(total_block - _n);
Chris@16:             for(std::size_t i = 0; i < total_block - _n; ++i) {
Chris@16:                 _rng();
Chris@16:             }
Chris@16:             _n = 0;
Chris@16:         }
Chris@16:         ++_n;
Chris@16:         return _rng();
Chris@16:     }
Chris@16: 
Chris@16:     void discard(boost::uintmax_t z)
Chris@16:     {
Chris@16:         for(boost::uintmax_t j = 0; j < z; ++j) {
Chris@16:             (*this)();
Chris@16:         }
Chris@16:     }
Chris@16: 
Chris@16:     template<class It>
Chris@16:     void generate(It first, It last)
Chris@16:     { detail::generate(*this, first, last); }
Chris@16: 
Chris@16:     /**
Chris@16:      * Returns the smallest value that the generator can produce.
Chris@16:      * This is the same as the minimum of the underlying generator.
Chris@16:      */
Chris@16:     static result_type min BOOST_PREVENT_MACRO_SUBSTITUTION ()
Chris@16:     { return (base_type::min)(); }
Chris@16:     /**
Chris@16:      * Returns the largest value that the generator can produce.
Chris@16:      * This is the same as the maximum of the underlying generator.
Chris@16:      */
Chris@16:     static result_type max BOOST_PREVENT_MACRO_SUBSTITUTION ()
Chris@16:     { return (base_type::max)(); }
Chris@16: 
Chris@16: #ifndef BOOST_RANDOM_NO_STREAM_OPERATORS
Chris@16:     /** Writes a \discard_block_engine to a @c std::ostream. */
Chris@16:     template<class CharT, class Traits>
Chris@16:     friend std::basic_ostream<CharT,Traits>&
Chris@16:     operator<<(std::basic_ostream<CharT,Traits>& os,
Chris@16:                const discard_block_engine& s)
Chris@16:     {
Chris@16:         os << s._rng << ' ' << s._n;
Chris@16:         return os;
Chris@16:     }
Chris@16: 
Chris@16:     /** Reads a \discard_block_engine from a @c std::istream. */
Chris@16:     template<class CharT, class Traits>
Chris@16:     friend std::basic_istream<CharT,Traits>&
Chris@16:     operator>>(std::basic_istream<CharT,Traits>& is, discard_block_engine& s)
Chris@16:     {
Chris@16:         is >> s._rng >> std::ws >> s._n;
Chris@16:         return is;
Chris@16:     }
Chris@16: #endif
Chris@16: 
Chris@16:     /** Returns true if the two generators will produce identical sequences. */
Chris@16:     friend bool operator==(const discard_block_engine& x,
Chris@16:                            const discard_block_engine& y)
Chris@16:     { return x._rng == y._rng && x._n == y._n; }
Chris@16:     /** Returns true if the two generators will produce different sequences. */
Chris@16:     friend bool operator!=(const discard_block_engine& x,
Chris@16:                            const discard_block_engine& y)
Chris@16:     { return !(x == y); }
Chris@16: 
Chris@16: private:
Chris@16:     base_type _rng;
Chris@16:     std::size_t _n;
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 URNG, std::size_t p, std::size_t r>
Chris@16: const bool discard_block_engine<URNG, p, r>::has_fixed_range;
Chris@16: template<class URNG, std::size_t p, std::size_t r>
Chris@16: const std::size_t discard_block_engine<URNG, p, r>::total_block;
Chris@16: template<class URNG, std::size_t p, std::size_t r>
Chris@16: const std::size_t discard_block_engine<URNG, p, r>::returned_block;
Chris@16: template<class URNG, std::size_t p, std::size_t r>
Chris@16: const std::size_t discard_block_engine<URNG, p, r>::block_size;
Chris@16: template<class URNG, std::size_t p, std::size_t r>
Chris@16: const std::size_t discard_block_engine<URNG, p, r>::used_block;
Chris@16: #endif
Chris@16: 
Chris@16: /// \cond \show_deprecated
Chris@16: 
Chris@16: template<class URNG, int p, int r>
Chris@16: class discard_block : public discard_block_engine<URNG, p, r>
Chris@16: {
Chris@16:     typedef discard_block_engine<URNG, p, r> base_t;
Chris@16: public:
Chris@16:     typedef typename base_t::result_type result_type;
Chris@16:     discard_block() {}
Chris@16:     template<class T>
Chris@16:     discard_block(T& arg) : base_t(arg) {}
Chris@16:     template<class T>
Chris@16:     discard_block(const T& arg) : base_t(arg) {}
Chris@16:     template<class It>
Chris@16:     discard_block(It& first, It last) : base_t(first, last) {}
Chris@16:     result_type min BOOST_PREVENT_MACRO_SUBSTITUTION ()
Chris@16:     { return (this->base().min)(); }
Chris@16:     result_type max BOOST_PREVENT_MACRO_SUBSTITUTION ()
Chris@16:     { return (this->base().max)(); }
Chris@16: };
Chris@16: 
Chris@16: /// \endcond
Chris@16: 
Chris@16: namespace detail {
Chris@16: 
Chris@16:     template<class Engine>
Chris@16:     struct generator_bits;
Chris@16:     
Chris@16:     template<class URNG, std::size_t p, std::size_t r>
Chris@16:     struct generator_bits<discard_block_engine<URNG, p, r> > {
Chris@16:         static std::size_t value() { return generator_bits<URNG>::value(); }
Chris@16:     };
Chris@16: 
Chris@16:     template<class URNG, int p, int r>
Chris@16:     struct generator_bits<discard_block<URNG, p, r> > {
Chris@16:         static std::size_t value() { return generator_bits<URNG>::value(); }
Chris@16:     };
Chris@16: 
Chris@16: }
Chris@16: 
Chris@16: } // namespace random
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #endif // BOOST_RANDOM_DISCARD_BLOCK_HPP