///////////////////////////////////////////////////////////////////////////////
// tail.hpp
//
// Copyright 2005 Eric Niebler, Michael Gauckler. 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)
#ifndef BOOST_ACCUMULATORS_STATISTICS_TAIL_HPP_EAN_28_10_2005
#define BOOST_ACCUMULATORS_STATISTICS_TAIL_HPP_EAN_28_10_2005
#include <vector>
#include <functional>
#include <boost/assert.hpp>
#include <boost/range.hpp>
#include <boost/mpl/if.hpp>
#include <boost/mpl/or.hpp>
#include <boost/mpl/placeholders.hpp>
#include <boost/parameter/keyword.hpp>
#include <boost/iterator/reverse_iterator.hpp>
#include <boost/iterator/permutation_iterator.hpp>
#include <boost/accumulators/framework/accumulator_base.hpp>
#include <boost/accumulators/framework/extractor.hpp>
#include <boost/accumulators/numeric/functional.hpp>
#include <boost/accumulators/framework/parameters/sample.hpp>
#include <boost/accumulators/framework/depends_on.hpp>
#include <boost/accumulators/statistics_fwd.hpp>
namespace boost { namespace accumulators
{
///////////////////////////////////////////////////////////////////////////////
// cache_size named parameters
BOOST_PARAMETER_NESTED_KEYWORD(tag, right_tail_cache_size, cache_size)
BOOST_PARAMETER_NESTED_KEYWORD(tag, left_tail_cache_size, cache_size)
namespace detail
{
///////////////////////////////////////////////////////////////////////////////
// tail_range
/// INTERNAL ONLY
///
template<typename ElementIterator, typename IndexIterator>
struct tail_range
{
typedef boost::iterator_range<
boost::reverse_iterator<boost::permutation_iterator<ElementIterator, IndexIterator> >
> type;
};
///////////////////////////////////////////////////////////////////////////////
// make_tail_range
/// INTERNAL ONLY
///
template<typename ElementIterator, typename IndexIterator>
typename tail_range<ElementIterator, IndexIterator>::type
make_tail_range(ElementIterator elem_begin, IndexIterator index_begin, IndexIterator index_end)
{
return boost::make_iterator_range(
boost::make_reverse_iterator(
boost::make_permutation_iterator(elem_begin, index_end)
)
, boost::make_reverse_iterator(
boost::make_permutation_iterator(elem_begin, index_begin)
)
);
}
///////////////////////////////////////////////////////////////////////////////
// stat_assign_visitor
/// INTERNAL ONLY
///
template<typename Args>
struct stat_assign_visitor
{
stat_assign_visitor(Args const &a, std::size_t i)
: args(a)
, index(i)
{
}
template<typename Stat>
void operator ()(Stat &stat) const
{
stat.assign(this->args, this->index);
}
private:
stat_assign_visitor &operator =(stat_assign_visitor const &);
Args const &args;
std::size_t index;
};
///////////////////////////////////////////////////////////////////////////////
// stat_assign
/// INTERNAL ONLY
///
template<typename Args>
inline stat_assign_visitor<Args> const stat_assign(Args const &args, std::size_t index)
{
return stat_assign_visitor<Args>(args, index);
}
///////////////////////////////////////////////////////////////////////////////
// is_tail_variate_feature
/// INTERNAL ONLY
///
template<typename Stat, typename LeftRight>
struct is_tail_variate_feature
: mpl::false_
{
};
/// INTERNAL ONLY
///
template<typename VariateType, typename VariateTag, typename LeftRight>
struct is_tail_variate_feature<tag::tail_variate<VariateType, VariateTag, LeftRight>, LeftRight>
: mpl::true_
{
};
/// INTERNAL ONLY
///
template<typename LeftRight>
struct is_tail_variate_feature<tag::tail_weights<LeftRight>, LeftRight>
: mpl::true_
{
};
} // namespace detail
namespace impl
{
///////////////////////////////////////////////////////////////////////////////
// tail_impl
template<typename Sample, typename LeftRight>
struct tail_impl
: accumulator_base
{
// LeftRight must be either right or left
BOOST_MPL_ASSERT((
mpl::or_<is_same<LeftRight, right>, is_same<LeftRight, left> >
));
typedef
typename mpl::if_<
is_same<LeftRight, right>
, numeric::functional::greater<Sample const, Sample const>
, numeric::functional::less<Sample const, Sample const>
>::type
predicate_type;
// for boost::result_of
typedef typename detail::tail_range<
typename std::vector<Sample>::const_iterator
, std::vector<std::size_t>::iterator
>::type result_type;
template<typename Args>
tail_impl(Args const &args)
: is_sorted(false)
, indices()
, samples(args[tag::tail<LeftRight>::cache_size], args[sample | Sample()])
{
this->indices.reserve(this->samples.size());
}
tail_impl(tail_impl const &that)
: is_sorted(that.is_sorted)
, indices(that.indices)
, samples(that.samples)
{
this->indices.reserve(this->samples.size());
}
// This just stores the heap and the samples.
// In operator()() below, if we are adding a new sample
// to the sample cache, we force all the
// tail_variates to update also. (It's not
// good enough to wait for the accumulator_set to do it
// for us because then information about whether a sample
// was stored and where is lost, and would need to be
// queried at runtime, which would be slow.) This is
// implemented as a filtered visitation over the stats,
// which we can access because args[accumulator] gives us
// all the stats.
template<typename Args>
void operator ()(Args const &args)
{
if(this->indices.size() < this->samples.size())
{
this->indices.push_back(this->indices.size());
this->assign(args, this->indices.back());
}
else if(predicate_type()(args[sample], this->samples[this->indices[0]]))
{
std::pop_heap(this->indices.begin(), this->indices.end(), indirect_cmp(this->samples));
this->assign(args, this->indices.back());
}
}
result_type result(dont_care) const
{
if(!this->is_sorted)
{
// Must use the same predicate here as in push_heap/pop_heap above.
std::sort_heap(this->indices.begin(), this->indices.end(), indirect_cmp(this->samples));
// sort_heap puts elements in reverse order. Calling std::reverse
// turns the sorted sequence back into a valid heap.
std::reverse(this->indices.begin(), this->indices.end());
this->is_sorted = true;
}
return detail::make_tail_range(
this->samples.begin()
, this->indices.begin()
, this->indices.end()
);
}
private:
struct is_tail_variate
{
template<typename T>
struct apply
: detail::is_tail_variate_feature<
typename detail::feature_tag<T>::type
, LeftRight
>
{};
};
template<typename Args>
void assign(Args const &args, std::size_t index)
{
BOOST_ASSERT(index < this->samples.size());
this->samples[index] = args[sample];
std::push_heap(this->indices.begin(), this->indices.end(), indirect_cmp(this->samples));
this->is_sorted = false;
// Tell the tail variates to store their values also
args[accumulator].template visit_if<is_tail_variate>(detail::stat_assign(args, index));
}
///////////////////////////////////////////////////////////////////////////////
//
struct indirect_cmp
: std::binary_function<std::size_t, std::size_t, bool>
{
indirect_cmp(std::vector<Sample> const &s)
: samples(s)
{
}
bool operator ()(std::size_t left, std::size_t right) const
{
return predicate_type()(this->samples[left], this->samples[right]);
}
private:
indirect_cmp &operator =(indirect_cmp const &);
std::vector<Sample> const &samples;
};
mutable bool is_sorted;
mutable std::vector<std::size_t> indices;
std::vector<Sample> samples;
};
} // namespace impl
// TODO The templatized tag::tail below should inherit from the correct named parameter.
// The following lines provide a workaround, but there must be a better way of doing this.
template<typename T>
struct tail_cache_size_named_arg
{
};
template<>
struct tail_cache_size_named_arg<left>
: tag::left_tail_cache_size
{
};
template<>
struct tail_cache_size_named_arg<right>
: tag::right_tail_cache_size
{
};
///////////////////////////////////////////////////////////////////////////////
// tag::tail<>
//
namespace tag
{
template<typename LeftRight>
struct tail
: depends_on<>
, tail_cache_size_named_arg<LeftRight>
{
/// INTERNAL ONLY
///
typedef accumulators::impl::tail_impl<mpl::_1, LeftRight> impl;
#ifdef BOOST_ACCUMULATORS_DOXYGEN_INVOKED
/// tag::tail<LeftRight>::cache_size named parameter
static boost::parameter::keyword<tail_cache_size_named_arg<LeftRight> > const cache_size;
#endif
};
struct abstract_tail
: depends_on<>
{
};
}
///////////////////////////////////////////////////////////////////////////////
// extract::tail
//
namespace extract
{
extractor<tag::abstract_tail> const tail = {};
BOOST_ACCUMULATORS_IGNORE_GLOBAL(tail)
}
using extract::tail;
template<typename LeftRight>
struct feature_of<tag::tail<LeftRight> >
: feature_of<tag::abstract_tail>
{
};
}} // namespace boost::accumulators
#endif
Submit an article or tip