132 lines
4.9 KiB
C++
132 lines
4.9 KiB
C++
// (C) Copyright 2007 Andrew Sutton
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//
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// Use, modification and distribution are subject to the
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// Boost Software License, Version 1.0 (See accompanying file
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// LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_GRAPH_DETAIL_GEODESIC_HPP
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#define BOOST_GRAPH_DETAIL_GEODESIC_HPP
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#include <functional>
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#include <boost/config.hpp>
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#include <boost/graph/graph_concepts.hpp>
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#include <boost/graph/numeric_values.hpp>
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#include <boost/concept/assert.hpp>
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// TODO: Should this really be in detail?
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namespace boost
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{
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// This is a very good discussion on centrality measures. While I can't
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// say that this has been the motivating factor for the design and
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// implementation of ths centrality framework, it does provide a single
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// point of reference for defining things like degree and closeness
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// centrality. Plus, the bibliography seems fairly complete.
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//
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// @article{citeulike:1144245,
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// author = {Borgatti, Stephen P. and Everett, Martin G.},
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// citeulike-article-id = {1144245},
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// doi = {10.1016/j.socnet.2005.11.005},
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// journal = {Social Networks},
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// month = {October},
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// number = {4},
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// pages = {466--484},
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// priority = {0},
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// title = {A Graph-theoretic perspective on centrality},
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// url = {http://dx.doi.org/10.1016/j.socnet.2005.11.005},
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// volume = {28},
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// year = {2006}
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// }
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// }
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namespace detail {
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// Note that this assumes T == property_traits<DistanceMap>::value_type
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// and that the args and return of combine are also T.
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template <typename Graph,
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typename DistanceMap,
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typename Combinator,
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typename Distance>
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inline Distance
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combine_distances(const Graph& g,
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DistanceMap dist,
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Combinator combine,
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Distance init)
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{
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BOOST_CONCEPT_ASSERT(( VertexListGraphConcept<Graph> ));
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typedef typename graph_traits<Graph>::vertex_descriptor Vertex;
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typedef typename graph_traits<Graph>::vertex_iterator VertexIterator;
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BOOST_CONCEPT_ASSERT(( ReadablePropertyMapConcept<DistanceMap,Vertex> ));
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BOOST_CONCEPT_ASSERT(( NumericValueConcept<Distance> ));
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typedef numeric_values<Distance> DistanceNumbers;
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BOOST_CONCEPT_ASSERT(( AdaptableBinaryFunction<Combinator,Distance,Distance,Distance> ));
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// If there's ever an infinite distance, then we simply return
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// infinity. Note that this /will/ include the a non-zero
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// distance-to-self in the combined values. However, this is usually
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// zero, so it shouldn't be too problematic.
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Distance ret = init;
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VertexIterator i, end;
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for(boost::tie(i, end) = vertices(g); i != end; ++i) {
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Vertex v = *i;
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if(get(dist, v) != DistanceNumbers::infinity()) {
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ret = combine(ret, get(dist, v));
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}
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else {
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ret = DistanceNumbers::infinity();
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break;
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}
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}
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return ret;
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}
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// Similar to std::plus<T>, but maximizes parameters
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// rather than adding them.
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template <typename T>
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struct maximize : public std::binary_function<T, T, T>
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{
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T operator ()(T x, T y) const
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{ BOOST_USING_STD_MAX(); return max BOOST_PREVENT_MACRO_SUBSTITUTION (x, y); }
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};
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// Another helper, like maximize() to help abstract functional
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// concepts. This is trivially instantiated for builtin numeric
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// types, but should be specialized for those types that have
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// discrete notions of reciprocals.
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template <typename T>
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struct reciprocal : public std::unary_function<T, T>
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{
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typedef std::unary_function<T, T> function_type;
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typedef typename function_type::result_type result_type;
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typedef typename function_type::argument_type argument_type;
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T operator ()(T t)
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{ return T(1) / t; }
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};
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} /* namespace detail */
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// This type defines the basic facilities used for computing values
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// based on the geodesic distances between vertices. Examples include
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// closeness centrality and mean geodesic distance.
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template <typename Graph, typename DistanceType, typename ResultType>
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struct geodesic_measure
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{
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typedef DistanceType distance_type;
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typedef ResultType result_type;
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typedef typename graph_traits<Graph>::vertices_size_type size_type;
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typedef numeric_values<distance_type> distance_values;
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typedef numeric_values<result_type> result_values;
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static inline distance_type infinite_distance()
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{ return distance_values::infinity(); }
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static inline result_type infinite_result()
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{ return result_values::infinity(); }
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static inline result_type zero_result()
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{ return result_values::zero(); }
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};
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} /* namespace boost */
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#endif
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