[857] | 1 | // Copyright 2004 The Trustees of Indiana University.
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| 2 |
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| 3 | // Use, modification and distribution is subject to the Boost Software
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| 4 | // License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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| 5 | // http://www.boost.org/LICENSE_1_0.txt)
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| 6 |
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| 7 | // Authors: Douglas Gregor
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| 8 | // Andrew Lumsdaine
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| 9 | #ifndef BOOST_GRAPH_ERDOS_RENYI_GENERATOR_HPP
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| 10 | #define BOOST_GRAPH_ERDOS_RENYI_GENERATOR_HPP
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| 11 |
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| 12 | #include <iterator>
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| 13 | #include <utility>
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| 14 | #include <boost/random/uniform_int.hpp>
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| 15 | #include <boost/graph/graph_traits.hpp>
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| 16 | #include <boost/type_traits/is_base_and_derived.hpp>
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| 17 | #include <boost/type_traits/is_same.hpp>
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| 18 |
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| 19 | namespace boost {
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| 20 |
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| 21 | template<typename RandomGenerator, typename Graph>
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| 22 | class erdos_renyi_iterator
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| 23 | {
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| 24 | typedef typename graph_traits<Graph>::directed_category directed_category;
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| 25 | typedef typename graph_traits<Graph>::vertices_size_type vertices_size_type;
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| 26 | typedef typename graph_traits<Graph>::edges_size_type edges_size_type;
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| 27 |
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| 28 | BOOST_STATIC_CONSTANT
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| 29 | (bool,
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| 30 | is_undirected = (is_base_and_derived<undirected_tag,
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| 31 | directed_category>::value
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| 32 | || is_same<undirected_tag, directed_category>::value));
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| 33 |
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| 34 | public:
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| 35 | typedef std::input_iterator_tag iterator_category;
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| 36 | typedef std::pair<vertices_size_type, vertices_size_type> value_type;
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| 37 | typedef const value_type& reference;
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| 38 | typedef const value_type* pointer;
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| 39 | typedef void difference_type;
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| 40 |
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| 41 | erdos_renyi_iterator() : gen(0), n(0), edges(0), allow_self_loops(false) {}
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| 42 | erdos_renyi_iterator(RandomGenerator& gen, vertices_size_type n,
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| 43 | double prob = 0.0, bool allow_self_loops = false)
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| 44 | : gen(&gen), n(n), edges(edges_size_type(prob * n * n)),
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| 45 | allow_self_loops(allow_self_loops)
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| 46 | {
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| 47 | if (is_undirected) edges = edges / 2;
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| 48 | next();
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| 49 | }
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| 50 |
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| 51 | reference operator*() const { return current; }
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| 52 | pointer operator->() const { return ¤t; }
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| 53 |
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| 54 | erdos_renyi_iterator& operator++()
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| 55 | {
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| 56 | --edges;
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| 57 | next();
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| 58 | return *this;
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| 59 | }
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| 60 |
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| 61 | erdos_renyi_iterator operator++(int)
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| 62 | {
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| 63 | erdos_renyi_iterator temp(*this);
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| 64 | ++(*this);
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| 65 | return temp;
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| 66 | }
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| 67 |
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| 68 | bool operator==(const erdos_renyi_iterator& other) const
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| 69 | { return edges == other.edges; }
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| 70 |
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| 71 | bool operator!=(const erdos_renyi_iterator& other) const
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| 72 | { return !(*this == other); }
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| 73 |
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| 74 | private:
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| 75 | void next()
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| 76 | {
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| 77 | uniform_int<vertices_size_type> rand_vertex(0, n-1);
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| 78 | current.first = rand_vertex(*gen);
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| 79 | do {
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| 80 | current.second = rand_vertex(*gen);
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| 81 | } while (current.first == current.second && !allow_self_loops);
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| 82 | }
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| 83 |
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| 84 | RandomGenerator* gen;
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| 85 | vertices_size_type n;
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| 86 | edges_size_type edges;
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| 87 | bool allow_self_loops;
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| 88 | value_type current;
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| 89 | };
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| 90 |
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| 91 | } // end namespace boost
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| 92 |
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| 93 | #endif // BOOST_GRAPH_ERDOS_RENYI_GENERATOR_HPP
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