You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and dots ('.'), can be up to 35 characters long. Letters must be lowercase.
97 lines
3.0 KiB
97 lines
3.0 KiB
/* boost random/generate_canonical.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: generate_canonical.hpp 72951 2011-07-07 04:57:37Z steven_watanabe $ |
|
* |
|
*/ |
|
|
|
#ifndef BOOST_RANDOM_GENERATE_CANONICAL_HPP |
|
#define BOOST_RANDOM_GENERATE_CANONICAL_HPP |
|
|
|
#include <algorithm> |
|
#include <boost/assert.hpp> |
|
#include <boost/config/no_tr1/cmath.hpp> |
|
#include <boost/limits.hpp> |
|
#include <boost/type_traits/is_integral.hpp> |
|
#include <boost/math/special_functions.hpp> |
|
#include <boost/random/detail/signed_unsigned_tools.hpp> |
|
#include <boost/random/detail/generator_bits.hpp> |
|
|
|
namespace boost { |
|
namespace random { |
|
|
|
namespace detail { |
|
|
|
template<class RealType, std::size_t bits, class URNG> |
|
RealType generate_canonical_impl(URNG& g, boost::mpl::true_ /*is_integral*/) |
|
{ |
|
using std::pow; |
|
typedef typename URNG::result_type base_result; |
|
std::size_t digits = std::numeric_limits<RealType>::digits; |
|
RealType R = RealType((g.max)()) - RealType((g.min)()) + 1; |
|
RealType mult = R; |
|
RealType limit = |
|
pow(RealType(2), |
|
RealType((std::min)(static_cast<std::size_t>(bits), digits))); |
|
RealType S = RealType(detail::subtract<base_result>()(g(), (g.min)())); |
|
while(mult < limit) { |
|
RealType inc = RealType(detail::subtract<base_result>()(g(), (g.min)())); |
|
S += inc * mult; |
|
mult *= R; |
|
} |
|
return S / mult; |
|
} |
|
|
|
template<class RealType, std::size_t bits, class URNG> |
|
RealType generate_canonical_impl(URNG& g, boost::mpl::false_ /*is_integral*/) |
|
{ |
|
using std::pow; |
|
using std::floor; |
|
BOOST_ASSERT((g.min)() == 0); |
|
BOOST_ASSERT((g.max)() == 1); |
|
typedef typename URNG::result_type base_result; |
|
std::size_t digits = std::numeric_limits<RealType>::digits; |
|
std::size_t engine_bits = detail::generator_bits<URNG>::value(); |
|
std::size_t b = (std::min)(bits, digits); |
|
RealType R = pow(RealType(2), RealType(engine_bits)); |
|
RealType mult = R; |
|
RealType limit = pow(RealType(2), RealType(b)); |
|
RealType S = RealType(g() - (g.min)()); |
|
while(mult < limit) { |
|
RealType inc(floor((RealType(g()) - RealType((g.min)())) * R)); |
|
S += inc * mult; |
|
mult *= R; |
|
} |
|
return S / mult; |
|
} |
|
|
|
} |
|
|
|
/** |
|
* Returns a value uniformly distributed in the range [0, 1) |
|
* with at least @c bits random bits. |
|
*/ |
|
template<class RealType, std::size_t bits, class URNG> |
|
RealType generate_canonical(URNG& g) |
|
{ |
|
RealType result = detail::generate_canonical_impl<RealType, bits>( |
|
g, boost::is_integral<typename URNG::result_type>()); |
|
BOOST_ASSERT(result >= 0); |
|
BOOST_ASSERT(result <= 1); |
|
if(result == 1) { |
|
result -= std::numeric_limits<RealType>::epsilon() / 2; |
|
BOOST_ASSERT(result != 1); |
|
} |
|
return result; |
|
} |
|
|
|
} // namespace random |
|
} // namespace boost |
|
|
|
#endif // BOOST_RANDOM_GENERATE_CANONICAL_HPP
|
|
|