272 lines
8.8 KiB
C++
272 lines
8.8 KiB
C++
|
/* boost random/independent_bits.hpp header file
|
||
|
|
*
|
||
|
|
* Copyright Steven Watanabe 2011
|
||
|
|
* Distributed under the Boost Software License, Version 1.0. (See
|
||
|
|
* accompanying file LICENSE_1_0.txt or copy at
|
||
|
|
* http://www.boost.org/LICENSE_1_0.txt)
|
||
|
|
*
|
||
|
|
* See http://www.boost.org for most recent version including documentation.
|
||
|
|
*
|
||
|
|
* $Id$
|
||
|
|
*
|
||
|
|
*/
|
||
|
|
|
||
|
|
#ifndef BOOST_RANDOM_INDEPENDENT_BITS_HPP
|
||
|
|
#define BOOST_RANDOM_INDEPENDENT_BITS_HPP
|
||
|
|
|
||
|
|
#include <istream>
|
||
|
|
#include <iosfwd>
|
||
|
|
#include <boost/assert.hpp>
|
||
|
|
#include <boost/limits.hpp>
|
||
|
|
#include <boost/config.hpp>
|
||
|
|
#include <boost/cstdint.hpp>
|
||
|
|
#include <boost/integer/integer_mask.hpp>
|
||
|
|
#include <boost/random/traits.hpp>
|
||
|
|
#include <boost/random/detail/config.hpp>
|
||
|
|
#include <boost/random/detail/integer_log2.hpp>
|
||
|
|
#include <boost/random/detail/operators.hpp>
|
||
|
|
#include <boost/random/detail/seed.hpp>
|
||
|
|
#include <boost/random/detail/seed_impl.hpp>
|
||
|
|
#include <boost/random/detail/signed_unsigned_tools.hpp>
|
||
|
|
|
||
|
|
namespace boost {
|
||
|
|
namespace random {
|
||
|
|
|
||
|
|
/**
|
||
|
|
* An instantiation of class template @c independent_bits_engine
|
||
|
|
* model a \pseudo_random_number_generator. It generates random
|
||
|
|
* numbers distributed between [0, 2^w) by combining one or
|
||
|
|
* more invocations of the base engine.
|
||
|
|
*
|
||
|
|
* Requires: 0 < w <= std::numeric_limits<UIntType>::digits
|
||
|
|
*/
|
||
|
|
template<class Engine, std::size_t w, class UIntType>
|
||
|
|
class independent_bits_engine
|
||
|
|
{
|
||
|
|
public:
|
||
|
|
typedef Engine base_type;
|
||
|
|
typedef UIntType result_type;
|
||
|
|
typedef typename Engine::result_type base_result_type;
|
||
|
|
|
||
|
|
// Required by old Boost.Random concept
|
||
|
|
BOOST_STATIC_CONSTANT(bool, has_fixed_range = false);
|
||
|
|
|
||
|
|
/** Returns the smallest value that the generator can produce. */
|
||
|
|
static result_type min BOOST_PREVENT_MACRO_SUBSTITUTION ()
|
||
|
|
{ return 0; }
|
||
|
|
/** Returns the largest value that the generator can produce. */
|
||
|
|
static result_type max BOOST_PREVENT_MACRO_SUBSTITUTION ()
|
||
|
|
{ return max_imp(boost::is_integral<UIntType>()); }
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Constructs an @c independent_bits_engine using the
|
||
|
|
* default constructor of the base generator.
|
||
|
|
*/
|
||
|
|
independent_bits_engine() { }
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Constructs an @c independent_bits_engine, using seed as
|
||
|
|
* the constructor argument for both base generators.
|
||
|
|
*/
|
||
|
|
BOOST_RANDOM_DETAIL_ARITHMETIC_CONSTRUCTOR(independent_bits_engine,
|
||
|
|
base_result_type, seed_arg)
|
||
|
|
{
|
||
|
|
_base.seed(seed_arg);
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Constructs an @c independent_bits_engine, using seq as
|
||
|
|
* the constructor argument for the base generator.
|
||
|
|
*/
|
||
|
|
BOOST_RANDOM_DETAIL_SEED_SEQ_CONSTRUCTOR(independent_bits_engine,
|
||
|
|
SeedSeq, seq)
|
||
|
|
{ _base.seed(seq); }
|
||
|
|
|
||
|
|
/** Constructs an @c independent_bits_engine by copying @c base. */
|
||
|
|
independent_bits_engine(const base_type& base_arg) : _base(base_arg) {}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Contructs an @c independent_bits_engine with
|
||
|
|
* values from the range defined by the input iterators first
|
||
|
|
* and last. first will be modified to point to the element
|
||
|
|
* after the last one used.
|
||
|
|
*
|
||
|
|
* Throws: @c std::invalid_argument if the input range is too small.
|
||
|
|
*
|
||
|
|
* Exception Safety: Basic
|
||
|
|
*/
|
||
|
|
template<class It>
|
||
|
|
independent_bits_engine(It& first, It last) : _base(first, last) { }
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Seeds an @c independent_bits_engine using the default
|
||
|
|
* seed of the base generator.
|
||
|
|
*/
|
||
|
|
void seed() { _base.seed(); }
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Seeds an @c independent_bits_engine, using @c seed as the
|
||
|
|
* seed for the base generator.
|
||
|
|
*/
|
||
|
|
BOOST_RANDOM_DETAIL_ARITHMETIC_SEED(independent_bits_engine,
|
||
|
|
base_result_type, seed_arg)
|
||
|
|
{ _base.seed(seed_arg); }
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Seeds an @c independent_bits_engine, using @c seq to
|
||
|
|
* seed the base generator.
|
||
|
|
*/
|
||
|
|
BOOST_RANDOM_DETAIL_SEED_SEQ_SEED(independent_bits_engine,
|
||
|
|
SeedSeq, seq)
|
||
|
|
{ _base.seed(seq); }
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Seeds an @c independent_bits_engine with
|
||
|
|
* values from the range defined by the input iterators first
|
||
|
|
* and last. first will be modified to point to the element
|
||
|
|
* after the last one used.
|
||
|
|
*
|
||
|
|
* Throws: @c std::invalid_argument if the input range is too small.
|
||
|
|
*
|
||
|
|
* Exception Safety: Basic
|
||
|
|
*/
|
||
|
|
template<class It> void seed(It& first, It last)
|
||
|
|
{ _base.seed(first, last); }
|
||
|
|
|
||
|
|
/** Returns the next value of the generator. */
|
||
|
|
result_type operator()()
|
||
|
|
{
|
||
|
|
// While it may seem wasteful to recalculate this
|
||
|
|
// every time, both msvc and gcc can propagate
|
||
|
|
// constants, resolving this at compile time.
|
||
|
|
base_unsigned range =
|
||
|
|
detail::subtract<base_result_type>()((_base.max)(), (_base.min)());
|
||
|
|
std::size_t m =
|
||
|
|
(range == (std::numeric_limits<base_unsigned>::max)()) ?
|
||
|
|
std::numeric_limits<base_unsigned>::digits :
|
||
|
|
detail::integer_log2(range + 1);
|
||
|
|
std::size_t n = (w + m - 1) / m;
|
||
|
|
std::size_t w0, n0;
|
||
|
|
base_unsigned y0, y1;
|
||
|
|
base_unsigned y0_mask, y1_mask;
|
||
|
|
calc_params(n, range, w0, n0, y0, y1, y0_mask, y1_mask);
|
||
|
|
if(base_unsigned(range - y0 + 1) > y0 / n) {
|
||
|
|
// increment n and try again.
|
||
|
|
++n;
|
||
|
|
calc_params(n, range, w0, n0, y0, y1, y0_mask, y1_mask);
|
||
|
|
}
|
||
|
|
|
||
|
|
BOOST_ASSERT(n0*w0 + (n - n0)*(w0 + 1) == w);
|
||
|
|
|
||
|
|
result_type S = 0;
|
||
|
|
for(std::size_t k = 0; k < n0; ++k) {
|
||
|
|
base_unsigned u;
|
||
|
|
do {
|
||
|
|
u = detail::subtract<base_result_type>()(_base(), (_base.min)());
|
||
|
|
} while(u > base_unsigned(y0 - 1));
|
||
|
|
S = (S << w0) + (u & y0_mask);
|
||
|
|
}
|
||
|
|
for(std::size_t k = 0; k < (n - n0); ++k) {
|
||
|
|
base_unsigned u;
|
||
|
|
do {
|
||
|
|
u = detail::subtract<base_result_type>()(_base(), (_base.min)());
|
||
|
|
} while(u > base_unsigned(y1 - 1));
|
||
|
|
S = (S << (w0 + 1)) + (u & y1_mask);
|
||
|
|
}
|
||
|
|
return S;
|
||
|
|
}
|
||
|
|
|
||
|
|
/** Fills a range with random values */
|
||
|
|
template<class Iter>
|
||
|
|
void generate(Iter first, Iter last)
|
||
|
|
{ detail::generate_from_int(*this, first, last); }
|
||
|
|
|
||
|
|
/** Advances the state of the generator by @c z. */
|
||
|
|
void discard(boost::uintmax_t z)
|
||
|
|
{
|
||
|
|
for(boost::uintmax_t i = 0; i < z; ++i) {
|
||
|
|
(*this)();
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
const base_type& base() const { return _base; }
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Writes the textual representation if the generator to a @c std::ostream.
|
||
|
|
* The textual representation of the engine is the textual representation
|
||
|
|
* of the base engine.
|
||
|
|
*/
|
||
|
|
BOOST_RANDOM_DETAIL_OSTREAM_OPERATOR(os, independent_bits_engine, r)
|
||
|
|
{
|
||
|
|
os << r._base;
|
||
|
|
return os;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Reads the state of an @c independent_bits_engine from a
|
||
|
|
* @c std::istream.
|
||
|
|
*/
|
||
|
|
BOOST_RANDOM_DETAIL_ISTREAM_OPERATOR(is, independent_bits_engine, r)
|
||
|
|
{
|
||
|
|
is >> r._base;
|
||
|
|
return is;
|
||
|
|
}
|
||
|
|
|
||
|
|
/**
|
||
|
|
* Returns: true iff the two @c independent_bits_engines will
|
||
|
|
* produce the same sequence of values.
|
||
|
|
*/
|
||
|
|
BOOST_RANDOM_DETAIL_EQUALITY_OPERATOR(independent_bits_engine, x, y)
|
||
|
|
{ return x._base == y._base; }
|
||
|
|
/**
|
||
|
|
* Returns: true iff the two @c independent_bits_engines will
|
||
|
|
* produce different sequences of values.
|
||
|
|
*/
|
||
|
|
BOOST_RANDOM_DETAIL_INEQUALITY_OPERATOR(independent_bits_engine)
|
||
|
|
|
||
|
|
private:
|
||
|
|
|
||
|
|
/// \cond show_private
|
||
|
|
typedef typename boost::random::traits::make_unsigned<base_result_type>::type base_unsigned;
|
||
|
|
|
||
|
|
static UIntType max_imp(const boost::true_type&)
|
||
|
|
{
|
||
|
|
return boost::low_bits_mask_t<w>::sig_bits;
|
||
|
|
}
|
||
|
|
static UIntType max_imp(const boost::false_type&)
|
||
|
|
{
|
||
|
|
// We have a multiprecision integer type:
|
||
|
|
BOOST_STATIC_ASSERT(std::numeric_limits<UIntType>::is_specialized);
|
||
|
|
return w < std::numeric_limits<UIntType>::digits ? UIntType((UIntType(1) << w) - 1) : UIntType((((UIntType(1) << (w - 1)) - 1) << 1) | 1u);
|
||
|
|
}
|
||
|
|
|
||
|
|
void calc_params(
|
||
|
|
std::size_t n, base_unsigned range,
|
||
|
|
std::size_t& w0, std::size_t& n0,
|
||
|
|
base_unsigned& y0, base_unsigned& y1,
|
||
|
|
base_unsigned& y0_mask, base_unsigned& y1_mask)
|
||
|
|
{
|
||
|
|
BOOST_ASSERT(w >= n);
|
||
|
|
w0 = w/n;
|
||
|
|
n0 = n - w % n;
|
||
|
|
y0_mask = (base_unsigned(2) << (w0 - 1)) - 1;
|
||
|
|
y1_mask = (y0_mask << 1) | 1;
|
||
|
|
y0 = (range + 1) & ~y0_mask;
|
||
|
|
y1 = (range + 1) & ~y1_mask;
|
||
|
|
BOOST_ASSERT(y0 != 0 || base_unsigned(range + 1) == 0);
|
||
|
|
}
|
||
|
|
/// \endcond
|
||
|
|
|
||
|
|
Engine _base;
|
||
|
|
};
|
||
|
|
|
||
|
|
#ifndef BOOST_NO_INCLASS_MEMBER_INITIALIZATION
|
||
|
|
template<class Engine, std::size_t w, class UIntType>
|
||
|
|
const bool independent_bits_engine<Engine, w, UIntType>::has_fixed_range;
|
||
|
|
#endif
|
||
|
|
|
||
|
|
} // namespace random
|
||
|
|
} // namespace boost
|
||
|
|
|
||
|
|
#endif // BOOST_RANDOM_INDEPENDENT_BITS_HPP
|