//=======================================================================
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// Copyright 1997, 1998, 1999, 2000 University of Notre Dame.
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// Authors: Andrew Lumsdaine, Lie-Quan Lee, Jeremy G. Siek
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//
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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//=======================================================================
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// Revision History:
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// 17 March 2006: Fixed a bug: when updating the degree a vertex
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// could be moved to a wrong bucket. (Roman Dementiev)
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//
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#ifndef BOOST_SMALLEST_LAST_VERTEX_ORDERING_HPP
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#define BOOST_SMALLEST_LAST_VERTEX_ORDERING_HPP
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/*
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The smallest-last ordering is defined for the loopless graph G with
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vertices a(j), j = 1,2,...,n where a(j) is the j-th column of A and
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with edge (a(i),a(j)) if and only if columns i and j have a
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non-zero in the same row position. The smallest-last ordering is
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determined recursively by letting list(k), k = n,...,1 be a column
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with least degree in the subgraph spanned by the un-ordered
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columns.
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*/
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#include <vector>
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#include <algorithm>
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#include <boost/config.hpp>
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#include <boost/graph/graph_traits.hpp>
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#include <boost/graph/properties.hpp>
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#include <boost/pending/bucket_sorter.hpp>
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namespace boost
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{
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template < class VertexListGraph, class Order, class Degree, class Marker >
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void smallest_last_vertex_ordering(
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const VertexListGraph& G, Order order, Degree degree, Marker marker)
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{
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typedef typename boost::graph_traits< VertexListGraph > GraphTraits;
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typedef typename GraphTraits::vertex_descriptor Vertex;
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// typedef typename GraphTraits::size_type size_type;
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typedef std::size_t size_type;
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const size_type num = num_vertices(G);
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typedef
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typename boost::property_map< VertexListGraph, vertex_index_t >::type
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ID;
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typedef bucket_sorter< size_type, Vertex, Degree, ID > BucketSorter;
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BucketSorter degree_bucket_sorter(num, num, degree, get(vertex_index, G));
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smallest_last_vertex_ordering(
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G, order, degree, marker, degree_bucket_sorter);
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}
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template < class VertexListGraph, class Order, class Degree, class Marker,
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class BucketSorter >
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void smallest_last_vertex_ordering(const VertexListGraph& G, Order order,
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Degree degree, Marker marker, BucketSorter& degree_buckets)
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{
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typedef typename boost::graph_traits< VertexListGraph > GraphTraits;
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typedef typename GraphTraits::vertex_descriptor Vertex;
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// typedef typename GraphTraits::size_type size_type;
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typedef std::size_t size_type;
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const size_type num = num_vertices(G);
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typename GraphTraits::vertex_iterator v, vend;
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for (boost::tie(v, vend) = vertices(G); v != vend; ++v)
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{
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put(marker, *v, num);
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put(degree, *v, out_degree(*v, G));
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degree_buckets.push(*v);
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}
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size_type minimum_degree = 0;
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size_type current_order = num - 1;
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while (1)
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{
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typedef typename BucketSorter::stack MDStack;
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MDStack minimum_degree_stack = degree_buckets[minimum_degree];
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while (minimum_degree_stack.empty())
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minimum_degree_stack = degree_buckets[++minimum_degree];
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Vertex node = minimum_degree_stack.top();
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put(order, current_order, node);
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if (current_order == 0) // find all vertices
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break;
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minimum_degree_stack.pop();
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put(marker, node, 0); // node has been ordered.
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typename GraphTraits::adjacency_iterator v, vend;
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for (boost::tie(v, vend) = adjacent_vertices(node, G); v != vend; ++v)
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if (get(marker, *v) > current_order)
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{ //*v is unordered vertex
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put(marker, *v,
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current_order); // mark the columns adjacent to node
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// delete *v from the bucket sorter
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degree_buckets.remove(*v);
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// It is possible minimum degree goes down
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// Here we keep tracking it.
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put(degree, *v, get(degree, *v) - 1);
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BOOST_USING_STD_MIN();
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minimum_degree = min BOOST_PREVENT_MACRO_SUBSTITUTION(
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minimum_degree, get(degree, *v));
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// reinsert *v in the bucket sorter with the new degree
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degree_buckets.push(*v);
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}
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current_order--;
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}
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// at this point, order[i] = v_i;
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}
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template < class VertexListGraph, class Order >
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void smallest_last_vertex_ordering(const VertexListGraph& G, Order order)
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{
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typedef typename graph_traits< VertexListGraph >::vertex_descriptor
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vertex_descriptor;
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typedef typename graph_traits< VertexListGraph >::degree_size_type
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degree_size_type;
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smallest_last_vertex_ordering(G, order,
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make_shared_array_property_map(
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num_vertices(G), degree_size_type(0), get(vertex_index, G)),
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make_shared_array_property_map(
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num_vertices(G), (std::size_t)(0), get(vertex_index, G)));
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}
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template < class VertexListGraph >
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std::vector< typename graph_traits< VertexListGraph >::vertex_descriptor >
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smallest_last_vertex_ordering(const VertexListGraph& G)
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{
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std::vector< typename graph_traits< VertexListGraph >::vertex_descriptor >
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o(num_vertices(G));
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smallest_last_vertex_ordering(G,
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make_iterator_property_map(
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o.begin(), typed_identity_property_map< std::size_t >()));
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return o;
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}
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}
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#endif
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