osrm-backend/data_structures/node_based_graph.hpp

/*

Copyright (c) 2015, Project OSRM contributors
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*/

#ifndef NODE_BASED_GRAPH_HPP
#define NODE_BASED_GRAPH_HPP

#include "dynamic_graph.hpp"
#include "import_edge.hpp"
#include "../util/simple_logger.hpp"

#include <tbb/parallel_sort.h>

#include <memory>

struct NodeBasedEdgeData
{
    NodeBasedEdgeData()
        : distance(INVALID_EDGE_WEIGHT), edgeBasedNodeID(SPECIAL_NODEID),
          nameID(std::numeric_limits<unsigned>::max()), isAccessRestricted(false), shortcut(false),
          forward(false), backward(false), roundabout(false), ignore_in_grid(false),
          travel_mode(TRAVEL_MODE_INACCESSIBLE)
    {
    }

    int distance;
    unsigned edgeBasedNodeID;
    unsigned nameID;
    bool isAccessRestricted : 1;
    bool shortcut : 1;
    bool forward : 1;
    bool backward : 1;
    bool roundabout : 1;
    bool ignore_in_grid : 1;
    TravelMode travel_mode : 4;

    void SwapDirectionFlags()
    {
        bool temp_flag = forward;
        forward = backward;
        backward = temp_flag;
    }

    bool IsCompatibleTo(const NodeBasedEdgeData &other) const
    {
        return (forward == other.forward) && (backward == other.backward) &&
               (nameID == other.nameID) && (ignore_in_grid == other.ignore_in_grid) &&
               (travel_mode == other.travel_mode);
    }
};

using NodeBasedDynamicGraph = DynamicGraph<NodeBasedEdgeData>;

// Factory method to create NodeBasedDynamicGraph from NodeBasedEdges
inline std::shared_ptr<NodeBasedDynamicGraph>
NodeBasedDynamicGraphFromImportEdges(int number_of_nodes, std::vector<NodeBasedEdge> &input_edge_list)
{
    static_assert(sizeof(NodeBasedEdgeData) == 16,
                  "changing node based edge data size changes memory consumption");

    DeallocatingVector<NodeBasedDynamicGraph::InputEdge> edges_list;
    NodeBasedDynamicGraph::InputEdge edge;
    for (const NodeBasedEdge &import_edge : input_edge_list)
    {
        BOOST_ASSERT(import_edge.forward || import_edge.backward);
        if (import_edge.forward)
        {
            edge.source = import_edge.source;
            edge.target = import_edge.target;
            edge.data.forward = import_edge.forward;
            edge.data.backward = import_edge.backward;
        }
        else
        {
            edge.source = import_edge.target;
            edge.target = import_edge.source;
            edge.data.backward = import_edge.forward;
            edge.data.forward = import_edge.backward;
        }

        if (edge.source == edge.target)
        {
            continue;
        }

        edge.data.distance = (std::max)(static_cast<int>(import_edge.weight), 1);
        BOOST_ASSERT(edge.data.distance > 0);
        edge.data.shortcut = false;
        edge.data.roundabout = import_edge.roundabout;
        edge.data.ignore_in_grid = import_edge.in_tiny_cc;
        edge.data.nameID = import_edge.name_id;
        edge.data.isAccessRestricted = import_edge.access_restricted;
        edge.data.travel_mode = import_edge.travel_mode;

        edges_list.push_back(edge);

        if (!import_edge.is_split)
        {
            using std::swap; // enable ADL
            swap(edge.source, edge.target);
            edge.data.SwapDirectionFlags();
            edges_list.push_back(edge);
        }
    }

    // sort edges by source node id
    tbb::parallel_sort(edges_list.begin(), edges_list.end());

    // this code removes multi-edges
    // my merging mutli-edges bi-directional edges can become directional again!
    // Consider the following example:
    // a --5-- b
    //  `--1--^
    // After merging we need to split {a, b, 5} into (a, b, 1) and (b, a, 5)
    NodeID edge_count = 0;
    for (NodeID i = 0; i < edges_list.size();)
    {
        const NodeID source = edges_list[i].source;
        const NodeID target = edges_list[i].target;
        // remove eigenloops
        if (source == target)
        {
            i++;
            continue;
        }
        NodeBasedDynamicGraph::InputEdge forward_edge;
        NodeBasedDynamicGraph::InputEdge reverse_edge;
        forward_edge = reverse_edge = edges_list[i];
        forward_edge.data.forward = reverse_edge.data.backward = true;
        forward_edge.data.backward = reverse_edge.data.forward = false;
        forward_edge.data.shortcut = reverse_edge.data.shortcut = false;
        forward_edge.data.distance = reverse_edge.data.distance = std::numeric_limits<int>::max();
        // remove parallel edges and set current distance values
        while (i < edges_list.size() && edges_list[i].source == source &&
               edges_list[i].target == target)
        {
            if (edges_list[i].data.forward)
            {
                forward_edge.data.distance =
                    std::min(edges_list[i].data.distance, forward_edge.data.distance);
            }
            if (edges_list[i].data.backward)
            {
                reverse_edge.data.distance =
                    std::min(edges_list[i].data.distance, reverse_edge.data.distance);
            }
            ++i;
        }
        // merge edges (s,t) and (t,s) into bidirectional edge
        if (forward_edge.data.distance == reverse_edge.data.distance)
        {
            if (static_cast<int>(forward_edge.data.distance) != std::numeric_limits<int>::max())
            {
                forward_edge.data.backward = true;
                BOOST_ASSERT(edge_count < i);
                edges_list[edge_count++] = forward_edge;
            }
        }
        else
        { // insert seperate edges
          // this case can only happen if we merged a bi-directional edge with a directional
          // edge above, this incrementing i and making it safe to overwrite the next element
          // as well
            if (static_cast<int>(forward_edge.data.distance) != std::numeric_limits<int>::max())
            {
                BOOST_ASSERT(edge_count < i);
                edges_list[edge_count++] = forward_edge;
            }
            if (static_cast<int>(reverse_edge.data.distance) != std::numeric_limits<int>::max())
            {
                BOOST_ASSERT(edge_count < i);
                edges_list[edge_count++] = reverse_edge;
            }
        }
    }
    edges_list.resize(edge_count);
    SimpleLogger().Write() << "merged " << edges_list.size() - edge_count << " edges out of "
                           << edges_list.size();

    return std::make_shared<NodeBasedDynamicGraph>(
        static_cast<NodeBasedDynamicGraph::NodeIterator>(number_of_nodes), edges_list);
}

#endif // NODE_BASED_GRAPH_HPP