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