--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/ossrv_pub/boost_apis/boost/graph/erdos_renyi_generator.hpp Tue Feb 02 02:01:42 2010 +0200
@@ -0,0 +1,228 @@
+// Copyright 2004, 2005 The Trustees of Indiana University.
+
+// 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)
+
+// Authors: Jeremiah Willcock
+// Douglas Gregor
+// Andrew Lumsdaine
+#ifndef BOOST_GRAPH_ERDOS_RENYI_GENERATOR_HPP
+#define BOOST_GRAPH_ERDOS_RENYI_GENERATOR_HPP
+
+#include <cassert>
+#include <iterator>
+#include <utility>
+#include <boost/shared_ptr.hpp>
+#include <boost/random/uniform_int.hpp>
+#include <boost/graph/graph_traits.hpp>
+#include <boost/random/geometric_distribution.hpp>
+#include <boost/type_traits/is_base_and_derived.hpp>
+#include <boost/type_traits/is_same.hpp>
+#include <cmath>
+
+namespace boost {
+
+ template<typename RandomGenerator, typename Graph>
+ class erdos_renyi_iterator
+ {
+ typedef typename graph_traits<Graph>::directed_category directed_category;
+ typedef typename graph_traits<Graph>::vertices_size_type vertices_size_type;
+ typedef typename graph_traits<Graph>::edges_size_type edges_size_type;
+
+ BOOST_STATIC_CONSTANT
+ (bool,
+ is_undirected = (is_base_and_derived<undirected_tag,
+ directed_category>::value
+ || is_same<undirected_tag, directed_category>::value));
+
+ public:
+ typedef std::input_iterator_tag iterator_category;
+ typedef std::pair<vertices_size_type, vertices_size_type> value_type;
+ typedef const value_type& reference;
+ typedef const value_type* pointer;
+ typedef void difference_type;
+
+ erdos_renyi_iterator() : gen(), n(0), edges(0), allow_self_loops(false) {}
+ erdos_renyi_iterator(RandomGenerator& gen, vertices_size_type n,
+ double fraction = 0.0, bool allow_self_loops = false)
+ : gen(&gen), n(n), edges(edges_size_type(fraction * n * n)),
+ allow_self_loops(allow_self_loops)
+ {
+ if (is_undirected) edges = edges / 2;
+ next();
+ }
+
+ erdos_renyi_iterator(RandomGenerator& gen, vertices_size_type n,
+ edges_size_type m, bool allow_self_loops = false)
+ : gen(&gen), n(n), edges(m),
+ allow_self_loops(allow_self_loops)
+ {
+ next();
+ }
+
+ reference operator*() const { return current; }
+ pointer operator->() const { return ¤t; }
+
+ erdos_renyi_iterator& operator++()
+ {
+ --edges;
+ next();
+ return *this;
+ }
+
+ erdos_renyi_iterator operator++(int)
+ {
+ erdos_renyi_iterator temp(*this);
+ ++(*this);
+ return temp;
+ }
+
+ bool operator==(const erdos_renyi_iterator& other) const
+ { return edges == other.edges; }
+
+ bool operator!=(const erdos_renyi_iterator& other) const
+ { return !(*this == other); }
+
+ private:
+ void next()
+ {
+ uniform_int<vertices_size_type> rand_vertex(0, n-1);
+ current.first = rand_vertex(*gen);
+ do {
+ current.second = rand_vertex(*gen);
+ } while (current.first == current.second && !allow_self_loops);
+ }
+
+ RandomGenerator* gen;
+ vertices_size_type n;
+ edges_size_type edges;
+ bool allow_self_loops;
+ value_type current;
+ };
+
+ template<typename RandomGenerator, typename Graph>
+ class sorted_erdos_renyi_iterator
+ {
+ typedef typename graph_traits<Graph>::directed_category directed_category;
+ typedef typename graph_traits<Graph>::vertices_size_type vertices_size_type;
+ typedef typename graph_traits<Graph>::edges_size_type edges_size_type;
+
+ BOOST_STATIC_CONSTANT
+ (bool,
+ is_undirected = (is_base_and_derived<undirected_tag,
+ directed_category>::value
+ || is_same<undirected_tag, directed_category>::value));
+
+ public:
+ typedef std::input_iterator_tag iterator_category;
+ typedef std::pair<vertices_size_type, vertices_size_type> value_type;
+ typedef const value_type& reference;
+ typedef const value_type* pointer;
+ typedef void difference_type;
+
+ sorted_erdos_renyi_iterator()
+ : gen(), rand_vertex(0.5), n(0), allow_self_loops(false),
+ src((std::numeric_limits<vertices_size_type>::max)()), tgt(0), prob(0) {}
+ sorted_erdos_renyi_iterator(RandomGenerator& gen, vertices_size_type n,
+ double prob = 0.0,
+ bool allow_self_loops = false)
+ : gen(),
+ // The "1.0 - prob" in the next line is to work around a Boost.Random
+ // (and TR1) bug in the specification of geometric_distribution. It
+ // should be replaced by "prob" when the issue is fixed.
+ rand_vertex(1.0 - prob),
+ n(n), allow_self_loops(allow_self_loops), src(0), tgt(0), prob(prob)
+ {
+ this->gen.reset(new uniform_01<RandomGenerator>(gen));
+
+ if (prob == 0.0) {src = (std::numeric_limits<vertices_size_type>::max)(); return;}
+ next();
+ }
+
+ reference operator*() const { return current; }
+ pointer operator->() const { return ¤t; }
+
+ sorted_erdos_renyi_iterator& operator++()
+ {
+ next();
+ return *this;
+ }
+
+ sorted_erdos_renyi_iterator operator++(int)
+ {
+ sorted_erdos_renyi_iterator temp(*this);
+ ++(*this);
+ return temp;
+ }
+
+ bool operator==(const sorted_erdos_renyi_iterator& other) const
+ { return src == other.src && tgt == other.tgt; }
+
+ bool operator!=(const sorted_erdos_renyi_iterator& other) const
+ { return !(*this == other); }
+
+ private:
+ void next()
+ {
+ using std::sqrt;
+ using std::floor;
+
+ // In order to get the edges from the generator in sorted order, one
+ // effective (but slow) procedure would be to use a
+ // bernoulli_distribution for each legal (src, tgt) pair. Because of the
+ // O(n^2) cost of that, a geometric distribution is used. The geometric
+ // distribution tells how many times the bernoulli_distribution would
+ // need to be run until it returns true. Thus, this distribution can be
+ // used to step through the edges which are actually present. Everything
+ // beyond "tgt += increment" is done to effectively convert linear
+ // indexing (the partial sums of the geometric distribution output) into
+ // graph edges.
+ assert (src != (std::numeric_limits<vertices_size_type>::max)());
+ vertices_size_type increment = rand_vertex(*gen);
+ tgt += increment;
+ if (is_undirected) {
+ // Update src and tgt based on position of tgt
+ // Basically, we want the greatest src_increment such that (in \bbQ):
+ // src_increment * (src + allow_self_loops + src_increment - 1/2) <= tgt
+ // The result of the LHS of this, evaluated with the computed
+ // src_increment, is then subtracted from tgt
+ double src_minus_half = (src + allow_self_loops) - 0.5;
+ double disc = src_minus_half * src_minus_half + 2 * tgt;
+ double src_increment_fp = floor(sqrt(disc) - src_minus_half);
+ vertices_size_type src_increment = vertices_size_type(src_increment_fp);
+ if (src + src_increment >= n) {
+ src = n;
+ } else {
+ tgt -= (src + allow_self_loops) * src_increment +
+ src_increment * (src_increment - 1) / 2;
+ src += src_increment;
+ }
+ } else {
+ // Number of out edge positions possible from each vertex in this graph
+ vertices_size_type possible_out_edges = n - (allow_self_loops ? 0 : 1);
+ src += (std::min)(n - src, tgt / possible_out_edges);
+ tgt %= possible_out_edges;
+ }
+ // Set end of graph code so (src, tgt) will be the same as for the end
+ // sorted_erdos_renyi_iterator
+ if (src >= n) {src = (std::numeric_limits<vertices_size_type>::max)(); tgt = 0;}
+ // Copy (src, tgt) into current
+ current.first = src;
+ current.second = tgt;
+ // Adjust for (src, src) edge being forbidden
+ if (!allow_self_loops && tgt >= src) ++current.second;
+ }
+
+ shared_ptr<uniform_01<RandomGenerator> > gen;
+ geometric_distribution<vertices_size_type> rand_vertex;
+ vertices_size_type n;
+ bool allow_self_loops;
+ vertices_size_type src, tgt;
+ value_type current;
+ double prob;
+ };
+
+} // end namespace boost
+
+#endif // BOOST_GRAPH_ERDOS_RENYI_GENERATOR_HPP