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src/boost/graph/distributed/crauser_et_al_shortest_paths.hpp  view on Meta::CPAN

                                 const MinInWeightMap& min_in_weight)
      : inherited(boost::graph::parallel::process_group(g), get(vertex_owner, g)),
        dist_queue(num_vertices(g),
                   dist_queue_compare_type(distance_map, compare),
                   id),
        out_queue(num_vertices(g),
                  out_queue_compare_type(distance_map, min_out_weight,
                                         combine, compare),
                  id),
        in_queue(num_vertices(g),
                 in_queue_compare_type(distance_map, min_in_weight,
                                       combine, compare),
                 id),
        g(g),
        distance_map(distance_map),
        predecessor_map(predecessor_map),
        min_out_weight(min_out_weight),
        min_in_weight(min_in_weight),
        min_distance(0),
        min_out_distance(0)
#ifdef PBGL_ACCOUNTING
        , local_deletions(0)
#endif
    { }

    void push(const value_type& x)
    {
      msg_value_type msg_value =
        msg_value_creator::create(get(distance_map, x),
                                  predecessor_value(get(predecessor_map, x)));
      inherited::update(x, msg_value);
    }

    void update(const value_type& x) { push(x); }

    void pop()
    {
      // Remove from distance queue
      dist_queue.remove(top_vertex);

      // Remove from OUT queue
      out_queue.remove(top_vertex);

      // Remove from IN queue
      in_queue.remove(top_vertex);

#ifdef PBGL_ACCOUNTING
      ++local_deletions;
#endif
    }

    vertex_descriptor& top() { return top_vertex; }
    const vertex_descriptor& top() const { return top_vertex; }

    bool empty()
    {
      inherited::collect();

      // If there are no suitable messages, wait until we get something
      while (!has_suitable_vertex()) {
        if (do_synchronize()) return true;
      }
      // Return true only if nobody has any messages; false if we
      // have suitable messages
      return false;
    }

    bool do_synchronize()
    {
      using boost::parallel::all_reduce;
      using boost::parallel::minimum;

      inherited::synchronize();

      // TBD: could use combine here, but then we need to stop using
      // minimum<distance_type>() as the function object.
      distance_type local_distances[2];
      local_distances[0] =
        dist_queue.empty()? (std::numeric_limits<distance_type>::max)()
        : get(distance_map, dist_queue.top());

      local_distances[1] =
        out_queue.empty()? (std::numeric_limits<distance_type>::max)()
        : (get(distance_map, out_queue.top())
           + get(min_out_weight, out_queue.top()));

      distance_type distances[2];
      all_reduce(this->process_group, local_distances, local_distances + 2,
                 distances, minimum<distance_type>());
      min_distance = distances[0];
      min_out_distance = distances[1];

#ifdef PBGL_ACCOUNTING
      std::size_t deletions = 0;
      all_reduce(this->process_group, &local_deletions, &local_deletions + 1,
                 &deletions, std::plus<std::size_t>());
      if (process_id(this->process_group) == 0) {
        crauser_et_al_shortest_paths_stats.deleted_vertices.push_back(deletions);
      }
      local_deletions = 0;
      BOOST_ASSERT(deletions > 0);
#endif

      return min_distance == (std::numeric_limits<distance_type>::max)();
    }

  private:
    vertex_descriptor predecessor_value(vertex_descriptor v) const
    { return v; }

    vertex_descriptor
    predecessor_value(property_traits<dummy_property_map>::reference) const
    { return graph_traits<Graph>::null_vertex(); }

    bool has_suitable_vertex() const
    {
      if (!dist_queue.empty()) {
        top_vertex = dist_queue.top();
        if (get(distance_map, dist_queue.top()) <= min_out_distance)
          return true;
      }

      if (!in_queue.empty()) {
        top_vertex = in_queue.top();
        return (get(distance_map, top_vertex)
                - get(min_in_weight, top_vertex)) <= min_distance;
      }
      return false;
    }

  public:
    void
    receive_update(process_id_type source, vertex_descriptor vertex,

src/boost/graph/distributed/crauser_et_al_shortest_paths.hpp  view on Meta::CPAN

          in_queue.push(vertex);
        }
        else {
          dist_queue.update(vertex);
          out_queue.update(vertex);
          in_queue.update(vertex);
        }
      }
    }

    void
    receive_update(process_id_type source, vertex_descriptor vertex,
                   std::pair<distance_type, vertex_descriptor> p)
    {
      if (p.first <= get(distance_map, vertex)) {
        put(predecessor_map, vertex, p.second);
        receive_update(source, vertex, p.first);
      }
    }

  private:
    dist_queue_type           dist_queue;
    out_queue_type            out_queue;
    in_queue_type             in_queue;
    mutable value_type        top_vertex;
    const Graph&              g;
    DistanceMap               distance_map;
    PredecessorMap            predecessor_map;
    MinOutWeightMap           min_out_weight;
    MinInWeightMap            min_in_weight;
    distance_type             min_distance;
    distance_type             min_out_distance;
#ifdef PBGL_ACCOUNTING
    std::size_t               local_deletions;
#endif
  };
  /************************************************************************/

  /************************************************************************
   * Initialize the property map that contains the minimum incoming edge  *
   * weight for each vertex. There are separate implementations for       *
   * directed, bidirectional, and undirected graph.                       *
   ************************************************************************/
  template<typename Graph, typename MinInWeightMap, typename WeightMap,
           typename Inf, typename Compare>
  void
  initialize_min_in_weights(const Graph& g, MinInWeightMap min_in_weight,
                            WeightMap weight, Inf inf, Compare compare,
                            directed_tag, incidence_graph_tag)
  {
    // Send minimum weights off to the owners
    set_property_map_role(vertex_distance, min_in_weight);
    BGL_FORALL_VERTICES_T(v, g, Graph) {
      BGL_FORALL_OUTEDGES_T(v, e, g, Graph) {
        if (get(weight, e) < get(min_in_weight, target(e, g)))
          put(min_in_weight, target(e, g), get(weight, e));
      }
    }

    using boost::graph::parallel::process_group;
    synchronize(process_group(g));

    // Replace any infinities with zeros
    BGL_FORALL_VERTICES_T(v, g, Graph) {
      if (get(min_in_weight, v) == inf) put(min_in_weight, v, 0);
    }
  }

  template<typename Graph, typename MinInWeightMap, typename WeightMap,
           typename Inf, typename Compare>
  void
  initialize_min_in_weights(const Graph& g, MinInWeightMap min_in_weight,
                            WeightMap weight, Inf inf, Compare compare,
                            directed_tag, bidirectional_graph_tag)
  {
#if 0
    typename property_map<Graph, vertex_local_t>::const_type
      local = get(vertex_local, g);

    // This code assumes that the properties of the in-edges are
    // available locally. This is not necessarily the case, so don't
    // do this yet.
    set_property_map_role(vertex_distance, min_in_weight);
    BGL_FORALL_VERTICES_T(v, g, Graph) {
      if (in_edges(v, g).first != in_edges(v, g).second) {
        std::cerr << "weights(" << g.distribution().global(get(local, v))
                  << ") = ";
        BGL_FORALL_INEDGES_T(v, e, g, Graph) {
          std::cerr << get(weight, e) << ' ';
        }
        std::cerr << std::endl;
        put(min_in_weight, v,
            *std::min_element
            (make_property_map_iterator(weight, in_edges(v, g).first),
             make_property_map_iterator(weight, in_edges(v, g).second),
             compare));
      } else {
        put(min_in_weight, v, 0);
      }
      std::cerr << "miw(" << g.distribution().global(get(local, v)) << ") = "
                << get(min_in_weight, v) << std::endl;
    }
#else
    initialize_min_in_weights(g, min_in_weight, weight, inf, compare,
                              directed_tag(), incidence_graph_tag());
#endif
  }

  template<typename Graph, typename MinInWeightMap, typename WeightMap,
           typename Inf, typename Compare>
  inline void
  initialize_min_in_weights(const Graph&, MinInWeightMap, WeightMap, Inf,
                            Compare, undirected_tag, bidirectional_graph_tag)
  {
    // In weights are the same as out weights, so do nothing
  }
  /************************************************************************/


  /************************************************************************
   * Initialize the property map that contains the minimum outgoing edge  *