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// Boost.Geometry Index
//
// R-tree R*-tree next node choosing algorithm implementation
//
// Copyright (c) 2011-2017 Adam Wulkiewicz, Lodz, Poland.
//
// Use, modification and distribution is subject to 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_GEOMETRY_INDEX_DETAIL_RTREE_RSTAR_CHOOSE_NEXT_NODE_HPP
#define BOOST_GEOMETRY_INDEX_DETAIL_RTREE_RSTAR_CHOOSE_NEXT_NODE_HPP
#include <algorithm>
#include <boost/geometry/algorithms/expand.hpp>
#include <boost/geometry/index/detail/algorithms/content.hpp>
#include <boost/geometry/index/detail/algorithms/intersection_content.hpp>
#include <boost/geometry/index/detail/algorithms/nth_element.hpp>
#include <boost/geometry/index/detail/algorithms/union_content.hpp>
#include <boost/geometry/index/detail/rtree/node/node.hpp>
#include <boost/geometry/index/detail/rtree/visitors/is_leaf.hpp>
namespace boost { namespace geometry { namespace index {
namespace detail { namespace rtree {
template <typename Value, typename Options, typename Box, typename Allocators>
class choose_next_node<Value, Options, Box, Allocators, choose_by_overlap_diff_tag>
{
typedef typename rtree::node<Value, typename Options::parameters_type, Box, Allocators, typename Options::node_tag>::type node;
typedef typename rtree::internal_node<Value, typename Options::parameters_type, Box, Allocators, typename Options::node_tag>::type internal_node;
typedef typename rtree::leaf<Value, typename Options::parameters_type, Box, Allocators, typename Options::node_tag>::type leaf;
typedef typename rtree::elements_type<internal_node>::type children_type;
typedef typename children_type::value_type child_type;
typedef typename Options::parameters_type parameters_type;
typedef typename index::detail::default_content_result<Box>::type content_type;
public:
template <typename Indexable>
static inline size_t apply(internal_node & n,
Indexable const& indexable,
parameters_type const& parameters,
size_t node_relative_level)
{
::boost::ignore_unused_variable_warning(parameters);
children_type & children = rtree::elements(n);
// children are leafs
if ( node_relative_level <= 1 )
{
return choose_by_minimum_overlap_cost(children, indexable, parameters.get_overlap_cost_threshold());
}
// children are internal nodes
else
return choose_by_minimum_content_cost(children, indexable);
}
private:
template <typename Indexable>
static inline size_t choose_by_minimum_overlap_cost(children_type const& children,
Indexable const& indexable,
size_t overlap_cost_threshold)
{
const size_t children_count = children.size();
content_type min_content_diff = (std::numeric_limits<content_type>::max)();
content_type min_content = (std::numeric_limits<content_type>::max)();
size_t choosen_index = 0;
// create container of children sorted by content enlargement needed to include the new value
typedef boost::tuple<size_t, content_type, content_type> child_contents;
typename rtree::container_from_elements_type<children_type, child_contents>::type children_contents;
children_contents.resize(children_count);
for ( size_t i = 0 ; i < children_count ; ++i )
{
child_type const& ch_i = children[i];
// expanded child node's box
Box box_exp(ch_i.first);
geometry::expand(box_exp, indexable);
// areas difference
content_type content = index::detail::content(box_exp);
content_type content_diff = content - index::detail::content(ch_i.first);
children_contents[i] = boost::make_tuple(i, content_diff, content);
if ( content_diff < min_content_diff ||
(content_diff == min_content_diff && content < min_content) )
{
min_content_diff = content_diff;
min_content = content;
choosen_index = i;
}
}
// is this assumption ok? if min_content_diff == 0 there is no overlap increase?
if ( min_content_diff < -std::numeric_limits<double>::epsilon() || std::numeric_limits<double>::epsilon() < min_content_diff )
{
size_t first_n_children_count = children_count;
if ( 0 < overlap_cost_threshold && overlap_cost_threshold < children.size() )
{
first_n_children_count = overlap_cost_threshold;
// rearrange by content_diff
// in order to calculate nearly minimum overlap cost
index::detail::nth_element(children_contents.begin(), children_contents.begin() + first_n_children_count, children_contents.end(), content_diff_less);
}
// calculate minimum or nearly minimum overlap cost
choosen_index = choose_by_minimum_overlap_cost_first_n(children, indexable, first_n_children_count, children_count, children_contents);
}
return choosen_index;
}
static inline bool content_diff_less(boost::tuple<size_t, content_type, content_type> const& p1, boost::tuple<size_t, content_type, content_type> const& p2)
{
return boost::get<1>(p1) < boost::get<1>(p2) ||
(boost::get<1>(p1) == boost::get<1>(p2) && boost::get<2>(p1) < boost::get<2>(p2));
}
template <typename Indexable, typename ChildrenContents>
static inline size_t choose_by_minimum_overlap_cost_first_n(children_type const& children,
Indexable const& indexable,
size_t const first_n_children_count,
size_t const children_count,
ChildrenContents const& children_contents)
{
BOOST_GEOMETRY_INDEX_ASSERT(first_n_children_count <= children_count, "unexpected value");
BOOST_GEOMETRY_INDEX_ASSERT(children_contents.size() == children_count, "unexpected number of elements");
// choose index with smallest overlap change value, or content change or smallest content
size_t choosen_index = 0;
content_type smallest_overlap_diff = (std::numeric_limits<content_type>::max)();
content_type smallest_content_diff = (std::numeric_limits<content_type>::max)();
content_type smallest_content = (std::numeric_limits<content_type>::max)();
// for each child node
for (size_t i = 0 ; i < first_n_children_count ; ++i )
{
child_type const& ch_i = children[i];
Box box_exp(ch_i.first);
// calculate expanded box of child node ch_i
geometry::expand(box_exp, indexable);
content_type overlap_diff = 0;
// calculate overlap
for ( size_t j = 0 ; j < children_count ; ++j )
{
if ( i != j )
{
child_type const& ch_j = children[j];
content_type overlap_exp = index::detail::intersection_content(box_exp, ch_j.first);
if ( overlap_exp < -std::numeric_limits<content_type>::epsilon() || std::numeric_limits<content_type>::epsilon() < overlap_exp )
{
overlap_diff += overlap_exp - index::detail::intersection_content(ch_i.first, ch_j.first);
}
}
}
content_type content = boost::get<2>(children_contents[i]);
content_type content_diff = boost::get<1>(children_contents[i]);
// update result
if ( overlap_diff < smallest_overlap_diff ||
( overlap_diff == smallest_overlap_diff && ( content_diff < smallest_content_diff ||
( content_diff == smallest_content_diff && content < smallest_content ) )
) )
{
smallest_overlap_diff = overlap_diff;
smallest_content_diff = content_diff;
smallest_content = content;
choosen_index = i;
}
}
return choosen_index;
}
template <typename Indexable>
static inline size_t choose_by_minimum_content_cost(children_type const& children, Indexable const& indexable)
{
size_t children_count = children.size();
// choose index with smallest content change or smallest content
size_t choosen_index = 0;
content_type smallest_content_diff = (std::numeric_limits<content_type>::max)();
content_type smallest_content = (std::numeric_limits<content_type>::max)();
// choose the child which requires smallest box expansion to store the indexable
for ( size_t i = 0 ; i < children_count ; ++i )
{
child_type const& ch_i = children[i];
// expanded child node's box
Box box_exp(ch_i.first);
geometry::expand(box_exp, indexable);
// areas difference
content_type content = index::detail::content(box_exp);
content_type content_diff = content - index::detail::content(ch_i.first);
// update the result
if ( content_diff < smallest_content_diff ||
( content_diff == smallest_content_diff && content < smallest_content ) )
{
smallest_content_diff = content_diff;
smallest_content = content;
choosen_index = i;
}
}
return choosen_index;
}
};
}} // namespace detail::rtree
}}} // namespace boost::geometry::index
#endif // BOOST_GEOMETRY_INDEX_DETAIL_RTREE_RSTAR_CHOOSE_NEXT_NODE_HPP
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