BoostGraphColoring.h

// Copyright (C) 2010 Garth N. Wells
//
// This file is part of DOLFIN.
//
// DOLFIN is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// DOLFIN is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with DOLFIN. If not, see <http://www.gnu.org/licenses/>.
//
// First added:  2010-11-24
// Last changed:

#ifndef __DOLFIN_BOOST_GRAPH_INTERFACE_H
#define __DOLFIN_BOOST_GRAPH_INTERFACE_H

#include <iostream>
#include <vector>

#include <boost/graph/adjacency_list.hpp>
#include <boost/graph/compressed_sparse_row_graph.hpp>
#include <boost/graph/sequential_vertex_coloring.hpp>
#include <dolfin/common/Timer.h>
#include "Graph.h"

namespace dolfin
{

  class Mesh;


  class BoostGraphColoring
  {

  public:

    template<typename ColorType>
      static std::size_t compute_local_vertex_coloring(const Graph& graph,
                                                       std::vector<ColorType>& colors)
    {
      Timer timer("Boost graph coloring (from dolfin::Graph)");

      // Typedef for Boost compressed sparse row graph
      typedef boost::compressed_sparse_row_graph<boost::directedS,
        boost::property<boost::vertex_color_t, ColorType> > BoostGraph;

      // Number of vertices
      const std::size_t n = graph.size();

      // Count number of edges
      Graph::const_iterator vertex;
      std::size_t num_edges = 0;
      for (vertex = graph.begin(); vertex != graph.end(); ++vertex)
        num_edges += vertex->size();

      // Build list of graph edges
      std::vector<std::pair<std::size_t, std::size_t> > edges;
      edges.reserve(num_edges);
      graph_set_type::const_iterator edge;
      for (vertex = graph.begin(); vertex != graph.end(); ++vertex)
      {
        for (edge = vertex->begin(); edge != vertex->end(); ++edge)
        {
          const std::size_t vertex_index = vertex - graph.begin();
          if (vertex_index != (std::size_t) *edge)
            edges.push_back(std::make_pair(vertex_index, *edge));
        }
      }
      // Build Boost graph
      const BoostGraph g(boost::edges_are_unsorted_multi_pass,
                         edges.begin(), edges.end(), n);

      // Resize vector to hold colors
      colors.resize(n);

      // Perform coloring
      return compute_local_vertex_coloring(g, colors);
    }

    template<typename T, typename ColorType>
    static std::size_t compute_local_vertex_coloring(const T& graph,
                                            std::vector<ColorType>& colors)
    {
      Timer timer("Boost graph coloring");

      // Number of vertices in graph
      const std::size_t num_vertices = boost::num_vertices(graph);
      dolfin_assert(num_vertices == colors.size());

      typedef typename boost::graph_traits<T>::vertices_size_type
        vert_size_type;
      typedef typename boost::property_map<T,
        boost::vertex_index_t>::const_type vert_index_map;

      // Resize to hold colors
      colors.resize(num_vertices);

      // Color vertices
      std::vector<vert_size_type> _colors(num_vertices);
      boost::iterator_property_map<vert_size_type*, vert_index_map>
          color(&_colors.front(), get(boost::vertex_index, graph));
      const vert_size_type num_colors = sequential_vertex_coloring(graph,
                                                                   color);

      // Copy colors and return
      std::copy(_colors.begin(), _colors.end(), colors.begin());
      return num_colors;
    }

  };
}

#endif