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140 lines
5.3 KiB
140 lines
5.3 KiB
//======================================================================= |
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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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template <class VertexListGraph, class Order, class Degree, class Marker> |
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void |
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smallest_last_vertex_ordering(const VertexListGraph& G, Order order, |
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Degree degree, Marker marker) { |
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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 typename boost::property_map<VertexListGraph, vertex_index_t>::type 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, |
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get(vertex_index,G)); |
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smallest_last_vertex_ordering(G, order, degree, marker, degree_bucket_sorter); |
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} |
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template <class VertexListGraph, class Order, class Degree, |
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class Marker, class BucketSorter> |
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void |
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smallest_last_vertex_ordering(const VertexListGraph& G, Order order, |
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Degree degree, Marker marker, |
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BucketSorter& degree_buckets) { |
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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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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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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 ) { //*v is unordered vertex |
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put(marker, *v, 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(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 |
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smallest_last_vertex_ordering(const VertexListGraph& G, Order order) { |
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typedef typename graph_traits<VertexListGraph>::vertex_descriptor vertex_descriptor; |
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typedef typename graph_traits<VertexListGraph>::degree_size_type degree_size_type; |
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smallest_last_vertex_ordering(G, order, |
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make_shared_array_property_map(num_vertices(G), degree_size_type(0), get(vertex_index, G)), |
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make_shared_array_property_map(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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std::vector<typename graph_traits<VertexListGraph>::vertex_descriptor> o(num_vertices(G)); |
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smallest_last_vertex_ordering(G, make_iterator_property_map(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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