510 lines
21 KiB
C++
510 lines
21 KiB
C++
#ifndef OSRM_ENGINE_ROUTING_BASE_MLD_HPP
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#define OSRM_ENGINE_ROUTING_BASE_MLD_HPP
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#include "engine/algorithm.hpp"
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#include "engine/datafacade.hpp"
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#include "engine/routing_algorithms/routing_base.hpp"
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#include "engine/search_engine_data.hpp"
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#include "util/typedefs.hpp"
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#include <boost/assert.hpp>
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#include <algorithm>
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#include <iterator>
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#include <limits>
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#include <tuple>
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#include <vector>
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namespace osrm
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{
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namespace engine
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{
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namespace routing_algorithms
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{
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namespace mld
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{
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namespace
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{
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// Unrestricted search (Args is const PhantomNodes &):
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// * use partition.GetQueryLevel to find the node query level based on source and target phantoms
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// * allow to traverse all cells
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template <typename MultiLevelPartition>
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inline LevelID getNodeQueryLevel(const MultiLevelPartition &partition,
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NodeID node,
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const PhantomNodes &phantom_nodes)
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{
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auto level = [&partition, node](const SegmentID &source, const SegmentID &target) {
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if (source.enabled && target.enabled)
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return partition.GetQueryLevel(source.id, target.id, node);
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return INVALID_LEVEL_ID;
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};
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return std::min(std::min(level(phantom_nodes.source_phantom.forward_segment_id,
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phantom_nodes.target_phantom.forward_segment_id),
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level(phantom_nodes.source_phantom.forward_segment_id,
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phantom_nodes.target_phantom.reverse_segment_id)),
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std::min(level(phantom_nodes.source_phantom.reverse_segment_id,
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phantom_nodes.target_phantom.forward_segment_id),
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level(phantom_nodes.source_phantom.reverse_segment_id,
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phantom_nodes.target_phantom.reverse_segment_id)));
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}
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inline bool checkParentCellRestriction(CellID, const PhantomNodes &) { return true; }
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// Restricted search (Args is LevelID, CellID):
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// * use the fixed level for queries
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// * check if the node cell is the same as the specified parent onr
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template <typename MultiLevelPartition>
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inline LevelID getNodeQueryLevel(const MultiLevelPartition &, NodeID, LevelID level, CellID)
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{
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return level;
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}
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inline bool checkParentCellRestriction(CellID cell, LevelID, CellID parent)
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{
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return cell == parent;
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}
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}
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// Heaps only record for each node its predecessor ("parent") on the shortest path.
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// For re-constructing the actual path we need to trace back all parent "pointers".
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// In contrast to the CH code MLD needs to know the edges (with clique arc property).
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using PackedEdge = std::tuple</*from*/ NodeID, /*to*/ NodeID, /*from_clique_arc*/ bool>;
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using PackedPath = std::vector<PackedEdge>;
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template <bool DIRECTION, typename OutIter>
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inline void retrievePackedPathFromSingleHeap(const SearchEngineData<Algorithm>::QueryHeap &heap,
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const NodeID middle,
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OutIter out)
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{
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NodeID current = middle;
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NodeID parent = heap.GetData(current).parent;
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while (current != parent)
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{
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const auto &data = heap.GetData(current);
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if (DIRECTION == FORWARD_DIRECTION)
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{
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*out = std::make_tuple(parent, current, data.from_clique_arc);
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++out;
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}
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else if (DIRECTION == REVERSE_DIRECTION)
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{
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*out = std::make_tuple(current, parent, data.from_clique_arc);
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++out;
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}
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current = parent;
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parent = heap.GetData(parent).parent;
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}
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}
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template <bool DIRECTION>
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inline PackedPath
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retrievePackedPathFromSingleHeap(const SearchEngineData<Algorithm>::QueryHeap &heap,
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const NodeID middle)
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{
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PackedPath packed_path;
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retrievePackedPathFromSingleHeap<DIRECTION>(heap, middle, std::back_inserter(packed_path));
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return packed_path;
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}
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// Trace path from middle to start in the forward search space (in reverse)
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// and from middle to end in the reverse search space. Middle connects paths.
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inline PackedPath
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retrievePackedPathFromHeap(const SearchEngineData<Algorithm>::QueryHeap &forward_heap,
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const SearchEngineData<Algorithm>::QueryHeap &reverse_heap,
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const NodeID middle)
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{
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// Retrieve start -> middle. Is in reverse order since tracing back starts from middle.
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auto packed_path = retrievePackedPathFromSingleHeap<FORWARD_DIRECTION>(forward_heap, middle);
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std::reverse(begin(packed_path), end(packed_path));
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// Retrieve middle -> end. Is already in correct order, tracing starts from middle.
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auto into = std::back_inserter(packed_path);
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retrievePackedPathFromSingleHeap<REVERSE_DIRECTION>(reverse_heap, middle, into);
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return packed_path;
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}
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template <bool DIRECTION, typename Algorithm, typename... Args>
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void relaxOutgoingEdges(const DataFacade<Algorithm> &facade,
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typename SearchEngineData<Algorithm>::QueryHeap &forward_heap,
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const NodeID node,
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const EdgeWeight weight,
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Args... args)
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{
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const auto &partition = facade.GetMultiLevelPartition();
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const auto &cells = facade.GetCellStorage();
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const auto &metric = facade.GetCellMetric();
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const auto level = getNodeQueryLevel(partition, node, args...);
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if (level >= 1 && !forward_heap.GetData(node).from_clique_arc)
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{
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if (DIRECTION == FORWARD_DIRECTION)
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{
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// Shortcuts in forward direction
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const auto &cell = cells.GetCell(metric, level, partition.GetCell(level, node));
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auto destination = cell.GetDestinationNodes().begin();
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for (auto shortcut_weight : cell.GetOutWeight(node))
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{
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BOOST_ASSERT(destination != cell.GetDestinationNodes().end());
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const NodeID to = *destination;
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if (shortcut_weight != INVALID_EDGE_WEIGHT && node != to)
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{
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const EdgeWeight to_weight = weight + shortcut_weight;
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BOOST_ASSERT(to_weight >= weight);
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if (!forward_heap.WasInserted(to))
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{
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forward_heap.Insert(to, to_weight, {node, true});
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}
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else if (to_weight < forward_heap.GetKey(to))
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{
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forward_heap.GetData(to) = {node, true};
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forward_heap.DecreaseKey(to, to_weight);
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}
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}
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++destination;
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}
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}
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else
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{
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// Shortcuts in backward direction
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const auto &cell = cells.GetCell(metric, level, partition.GetCell(level, node));
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auto source = cell.GetSourceNodes().begin();
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for (auto shortcut_weight : cell.GetInWeight(node))
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{
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BOOST_ASSERT(source != cell.GetSourceNodes().end());
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const NodeID to = *source;
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if (shortcut_weight != INVALID_EDGE_WEIGHT && node != to)
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{
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const EdgeWeight to_weight = weight + shortcut_weight;
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BOOST_ASSERT(to_weight >= weight);
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if (!forward_heap.WasInserted(to))
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{
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forward_heap.Insert(to, to_weight, {node, true});
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}
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else if (to_weight < forward_heap.GetKey(to))
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{
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forward_heap.GetData(to) = {node, true};
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forward_heap.DecreaseKey(to, to_weight);
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}
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}
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++source;
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}
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}
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}
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// Boundary edges
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for (const auto edge : facade.GetBorderEdgeRange(level, node))
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{
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const auto &edge_data = facade.GetEdgeData(edge);
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if (DIRECTION == FORWARD_DIRECTION ? edge_data.forward : edge_data.backward)
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{
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const NodeID to = facade.GetTarget(edge);
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if (!facade.ExcludeNode(to) &&
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checkParentCellRestriction(partition.GetCell(level + 1, to), args...))
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{
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BOOST_ASSERT_MSG(edge_data.weight > 0, "edge_weight invalid");
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const EdgeWeight to_weight = weight + edge_data.weight;
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if (!forward_heap.WasInserted(to))
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{
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forward_heap.Insert(to, to_weight, {node, false});
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}
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else if (to_weight < forward_heap.GetKey(to))
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{
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forward_heap.GetData(to) = {node, false};
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forward_heap.DecreaseKey(to, to_weight);
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}
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}
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}
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}
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}
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template <bool DIRECTION, typename Algorithm, typename... Args>
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void routingStep(const DataFacade<Algorithm> &facade,
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typename SearchEngineData<Algorithm>::QueryHeap &forward_heap,
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typename SearchEngineData<Algorithm>::QueryHeap &reverse_heap,
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NodeID &middle_node,
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EdgeWeight &path_upper_bound,
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const bool force_loop_forward,
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const bool force_loop_reverse,
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Args... args)
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{
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const auto node = forward_heap.DeleteMin();
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const auto weight = forward_heap.GetKey(node);
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BOOST_ASSERT(!facade.ExcludeNode(node));
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// Upper bound for the path source -> target with
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// weight(source -> node) = weight weight(to -> target) ≤ reverse_weight
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// is weight + reverse_weight
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// More tighter upper bound requires additional condition reverse_heap.WasRemoved(to)
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// with weight(to -> target) = reverse_weight and all weights ≥ 0
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if (reverse_heap.WasInserted(node))
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{
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auto reverse_weight = reverse_heap.GetKey(node);
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auto path_weight = weight + reverse_weight;
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// MLD uses loops forcing only to prune single node paths in forward and/or
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// backward direction (there is no need to force loops in MLD but in CH)
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if (!(force_loop_forward && forward_heap.GetData(node).parent == node) &&
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!(force_loop_reverse && reverse_heap.GetData(node).parent == node) &&
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(path_weight >= 0) && (path_weight < path_upper_bound))
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{
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middle_node = node;
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path_upper_bound = path_weight;
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}
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}
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// Relax outgoing edges from node
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relaxOutgoingEdges<DIRECTION>(facade, forward_heap, node, weight, args...);
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}
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// With (s, middle, t) we trace back the paths middle -> s and middle -> t.
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// This gives us a packed path (node ids) from the base graph around s and t,
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// and overlay node ids otherwise. We then have to unpack the overlay clique
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// edges by recursively descending unpacking the path down to the base graph.
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using UnpackedNodes = std::vector<NodeID>;
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using UnpackedEdges = std::vector<EdgeID>;
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using UnpackedPath = std::tuple<EdgeWeight, UnpackedNodes, UnpackedEdges>;
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template <typename Algorithm, typename... Args>
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UnpackedPath search(SearchEngineData<Algorithm> &engine_working_data,
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const DataFacade<Algorithm> &facade,
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typename SearchEngineData<Algorithm>::QueryHeap &forward_heap,
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typename SearchEngineData<Algorithm>::QueryHeap &reverse_heap,
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const bool force_loop_forward,
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const bool force_loop_reverse,
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EdgeWeight weight_upper_bound,
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Args... args)
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{
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if (forward_heap.Empty() || reverse_heap.Empty())
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{
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return std::make_tuple(INVALID_EDGE_WEIGHT, std::vector<NodeID>(), std::vector<EdgeID>());
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}
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const auto &partition = facade.GetMultiLevelPartition();
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BOOST_ASSERT(!forward_heap.Empty() && forward_heap.MinKey() < INVALID_EDGE_WEIGHT);
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BOOST_ASSERT(!reverse_heap.Empty() && reverse_heap.MinKey() < INVALID_EDGE_WEIGHT);
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// run two-Target Dijkstra routing step.
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NodeID middle = SPECIAL_NODEID;
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EdgeWeight weight = weight_upper_bound;
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EdgeWeight forward_heap_min = forward_heap.MinKey();
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EdgeWeight reverse_heap_min = reverse_heap.MinKey();
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while (forward_heap.Size() + reverse_heap.Size() > 0 &&
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forward_heap_min + reverse_heap_min < weight)
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{
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if (!forward_heap.Empty())
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{
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routingStep<FORWARD_DIRECTION>(facade,
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forward_heap,
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reverse_heap,
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middle,
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weight,
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force_loop_forward,
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force_loop_reverse,
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args...);
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if (!forward_heap.Empty())
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forward_heap_min = forward_heap.MinKey();
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}
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if (!reverse_heap.Empty())
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{
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routingStep<REVERSE_DIRECTION>(facade,
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reverse_heap,
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forward_heap,
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middle,
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weight,
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force_loop_reverse,
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force_loop_forward,
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args...);
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if (!reverse_heap.Empty())
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reverse_heap_min = reverse_heap.MinKey();
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}
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};
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// No path found for both target nodes?
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if (weight >= weight_upper_bound || SPECIAL_NODEID == middle)
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{
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return std::make_tuple(INVALID_EDGE_WEIGHT, std::vector<NodeID>(), std::vector<EdgeID>());
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}
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// Get packed path as edges {from node ID, to node ID, from_clique_arc}
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auto packed_path = retrievePackedPathFromHeap(forward_heap, reverse_heap, middle);
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// Beware the edge case when start, middle, end are all the same.
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// In this case we return a single node, no edges. We also don't unpack.
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const NodeID source_node = !packed_path.empty() ? std::get<0>(packed_path.front()) : middle;
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// Unpack path
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std::vector<NodeID> unpacked_nodes;
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std::vector<EdgeID> unpacked_edges;
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unpacked_nodes.reserve(packed_path.size());
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unpacked_edges.reserve(packed_path.size());
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unpacked_nodes.push_back(source_node);
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for (auto const &packed_edge : packed_path)
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{
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NodeID source, target;
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bool overlay_edge;
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std::tie(source, target, overlay_edge) = packed_edge;
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if (!overlay_edge)
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{ // a base graph edge
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unpacked_nodes.push_back(target);
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unpacked_edges.push_back(facade.FindEdge(source, target));
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}
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else
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{ // an overlay graph edge
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LevelID level = getNodeQueryLevel(partition, source, args...);
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CellID parent_cell_id = partition.GetCell(level, source);
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BOOST_ASSERT(parent_cell_id == partition.GetCell(level, target));
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LevelID sublevel = level - 1;
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// Here heaps can be reused, let's go deeper!
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forward_heap.Clear();
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reverse_heap.Clear();
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forward_heap.Insert(source, 0, {source});
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reverse_heap.Insert(target, 0, {target});
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// TODO: when structured bindings will be allowed change to
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// auto [subpath_weight, subpath_source, subpath_target, subpath] = ...
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EdgeWeight subpath_weight;
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std::vector<NodeID> subpath_nodes;
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std::vector<EdgeID> subpath_edges;
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std::tie(subpath_weight, subpath_nodes, subpath_edges) = search(engine_working_data,
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facade,
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forward_heap,
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reverse_heap,
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force_loop_forward,
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force_loop_reverse,
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INVALID_EDGE_WEIGHT,
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sublevel,
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parent_cell_id);
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BOOST_ASSERT(!subpath_edges.empty());
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BOOST_ASSERT(subpath_nodes.size() > 1);
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BOOST_ASSERT(subpath_nodes.front() == source);
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BOOST_ASSERT(subpath_nodes.back() == target);
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unpacked_nodes.insert(
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unpacked_nodes.end(), std::next(subpath_nodes.begin()), subpath_nodes.end());
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unpacked_edges.insert(unpacked_edges.end(), subpath_edges.begin(), subpath_edges.end());
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}
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}
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return std::make_tuple(weight, std::move(unpacked_nodes), std::move(unpacked_edges));
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}
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// Alias to be compatible with the CH-based search
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template <typename Algorithm>
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inline void search(SearchEngineData<Algorithm> &engine_working_data,
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const DataFacade<Algorithm> &facade,
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typename SearchEngineData<Algorithm>::QueryHeap &forward_heap,
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typename SearchEngineData<Algorithm>::QueryHeap &reverse_heap,
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EdgeWeight &weight,
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std::vector<NodeID> &unpacked_nodes,
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const bool force_loop_forward,
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const bool force_loop_reverse,
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const PhantomNodes &phantom_nodes,
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const EdgeWeight weight_upper_bound = INVALID_EDGE_WEIGHT)
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{
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// TODO: change search calling interface to use unpacked_edges result
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std::tie(weight, unpacked_nodes, std::ignore) = search(engine_working_data,
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facade,
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forward_heap,
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reverse_heap,
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force_loop_forward,
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force_loop_reverse,
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weight_upper_bound,
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phantom_nodes);
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}
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// TODO: refactor CH-related stub to use unpacked_edges
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template <typename RandomIter, typename FacadeT>
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void unpackPath(const FacadeT &facade,
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RandomIter packed_path_begin,
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RandomIter packed_path_end,
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const PhantomNodes &phantom_nodes,
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std::vector<PathData> &unpacked_path)
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{
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const auto nodes_number = std::distance(packed_path_begin, packed_path_end);
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BOOST_ASSERT(nodes_number > 0);
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std::vector<NodeID> unpacked_nodes;
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std::vector<EdgeID> unpacked_edges;
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unpacked_nodes.reserve(nodes_number);
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unpacked_edges.reserve(nodes_number);
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unpacked_nodes.push_back(*packed_path_begin);
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if (nodes_number > 1)
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{
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util::for_each_pair(
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packed_path_begin,
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packed_path_end,
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[&facade, &unpacked_nodes, &unpacked_edges](const auto from, const auto to) {
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unpacked_nodes.push_back(to);
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unpacked_edges.push_back(facade.FindEdge(from, to));
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});
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}
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annotatePath(facade, phantom_nodes, unpacked_nodes, unpacked_edges, unpacked_path);
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}
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template <typename Algorithm>
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double getNetworkDistance(SearchEngineData<Algorithm> &engine_working_data,
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const DataFacade<Algorithm> &facade,
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typename SearchEngineData<Algorithm>::QueryHeap &forward_heap,
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typename SearchEngineData<Algorithm>::QueryHeap &reverse_heap,
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const PhantomNode &source_phantom,
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const PhantomNode &target_phantom,
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EdgeWeight weight_upper_bound = INVALID_EDGE_WEIGHT)
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{
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forward_heap.Clear();
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reverse_heap.Clear();
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const PhantomNodes phantom_nodes{source_phantom, target_phantom};
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insertNodesInHeaps(forward_heap, reverse_heap, phantom_nodes);
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EdgeWeight weight = INVALID_EDGE_WEIGHT;
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std::vector<NodeID> unpacked_nodes;
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std::vector<EdgeID> unpacked_edges;
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std::tie(weight, unpacked_nodes, unpacked_edges) = search(engine_working_data,
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facade,
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forward_heap,
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reverse_heap,
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DO_NOT_FORCE_LOOPS,
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DO_NOT_FORCE_LOOPS,
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weight_upper_bound,
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phantom_nodes);
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if (weight == INVALID_EDGE_WEIGHT)
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{
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return std::numeric_limits<double>::max();
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}
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std::vector<PathData> unpacked_path;
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annotatePath(facade, phantom_nodes, unpacked_nodes, unpacked_edges, unpacked_path);
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return getPathDistance(facade, unpacked_path, source_phantom, target_phantom);
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}
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} // namespace mld
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} // namespace routing_algorithms
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} // namespace engine
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} // namespace osrm
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#endif // OSRM_ENGINE_ROUTING_BASE_MLD_HPP
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