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Simplify upper bound condition for MLD routing
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@oxidase
oxidase committed Mar 14, 2017
1 parent aecb92e commit 8582c3d
Showing 1 changed file with 29 additions and 58 deletions.
87 changes: 29 additions & 58 deletions include/engine/routing_algorithms/routing_base_mld.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -27,30 +27,24 @@ void routingStep(const datafacade::ContiguousInternalMemoryDataFacade<algorithm:
SearchEngineData::MultiLayerDijkstraHeap &reverse_heap,
const std::pair<LevelID, CellID> &parent_cell,
NodeID &middle_node,
EdgeWeight &path_upper_bound,
EdgeWeight &forward_upper_bound,
EdgeWeight &reverse_upper_bound)
EdgeWeight &path_upper_bound)
{
const auto node = forward_heap.DeleteMin();
const auto weight = forward_heap.GetKey(node);

auto update_upper_bounds = [&](NodeID to, EdgeWeight forward_weight, EdgeWeight edge_weight) {
// Upper bound for the path source -> target with
// weight(source -> node) = forward_weight, weight(node -> to) = edge_weight and
// weight(to -> target) ≤ reverse_weight is forward_weight + edge_weight + reverse_weight
// More tighter upper bound requires additional condition reverse_heap.WasRemoved(to)
// with weight(to -> target) = reverse_weight and all weights ≥ 0
if (reverse_heap.WasInserted(to))
// Upper bound for the path source -> target with
// weight(source -> node) = weight weight(to -> target) ≤ reverse_weight
// is weight + reverse_weight
// More tighter upper bound requires additional condition reverse_heap.WasRemoved(to)
// with weight(to -> target) = reverse_weight and all weights ≥ 0
if (reverse_heap.WasInserted(node))
{
auto reverse_weight = reverse_heap.GetKey(node);
auto path_weight = weight + reverse_weight;
if (path_weight >= 0 && path_weight < path_upper_bound)
{
auto reverse_weight = reverse_heap.GetKey(to);
auto path_weight = forward_weight + edge_weight + reverse_weight;
if (path_weight >= 0 && path_weight < path_upper_bound)
{
middle_node = to;
path_upper_bound = path_weight;
forward_upper_bound = forward_weight + edge_weight;
reverse_upper_bound = reverse_weight + edge_weight;
}
middle_node = node;
path_upper_bound = path_weight;
}
};

Expand All @@ -61,9 +55,6 @@ void routingStep(const datafacade::ContiguousInternalMemoryDataFacade<algorithm:
(node_data.parent == node || // is the first point of the path
node_data.edge_id != SPECIAL_EDGEID); // or an overlay entreé point

// Edge case: single node path
update_upper_bounds(node, weight, 0);

if (check_overlay_edges)
{
if (DIRECTION == FORWARD_DIRECTION)
Expand All @@ -81,13 +72,11 @@ void routingStep(const datafacade::ContiguousInternalMemoryDataFacade<algorithm:
if (!forward_heap.WasInserted(to))
{
forward_heap.Insert(to, to_weight, {node, level});
update_upper_bounds(to, weight, shortcut_weight);
}
else if (to_weight < forward_heap.GetKey(to))
{
forward_heap.GetData(to) = {node, level};
forward_heap.DecreaseKey(to, to_weight);
update_upper_bounds(to, weight, shortcut_weight);
}
}
++destination;
Expand All @@ -108,13 +97,11 @@ void routingStep(const datafacade::ContiguousInternalMemoryDataFacade<algorithm:
if (!forward_heap.WasInserted(to))
{
forward_heap.Insert(to, to_weight, {node, level});
update_upper_bounds(to, weight, shortcut_weight);
}
else if (to_weight < forward_heap.GetKey(to))
{
forward_heap.GetData(to) = {node, level};
forward_heap.DecreaseKey(to, to_weight);
update_upper_bounds(to, weight, shortcut_weight);
}
}
++source;
Expand Down Expand Up @@ -144,13 +131,11 @@ void routingStep(const datafacade::ContiguousInternalMemoryDataFacade<algorithm:
if (!forward_heap.WasInserted(to))
{
forward_heap.Insert(to, to_weight, {node, to_level, edge});
update_upper_bounds(to, weight, edge_data.weight);
}
else if (to_weight < forward_heap.GetKey(to))
{
forward_heap.GetData(to) = {node, to_level, edge};
forward_heap.DecreaseKey(to, to_weight);
update_upper_bounds(to, weight, edge_data.weight);
}
}
}
Expand All @@ -164,44 +149,30 @@ auto search(const datafacade::ContiguousInternalMemoryDataFacade<algorithm::MLD>
SearchEngineData::MultiLayerDijkstraHeap &reverse_heap,
const std::pair<LevelID, CellID> &parent_cell)
{
BOOST_ASSERT(!forward_heap.Empty() && forward_heap.MinKey() < INVALID_EDGE_WEIGHT);
BOOST_ASSERT(!reverse_heap.Empty() && reverse_heap.MinKey() < INVALID_EDGE_WEIGHT);

// run two-Target Dijkstra routing step.
NodeID middle = SPECIAL_NODEID;
EdgeWeight weight = INVALID_EDGE_WEIGHT;
EdgeWeight forward_search_radius = INVALID_EDGE_WEIGHT;
EdgeWeight reverse_search_radius = INVALID_EDGE_WEIGHT;
bool progress;
do
EdgeWeight forward_heap_min = forward_heap.MinKey();
EdgeWeight reverse_heap_min = reverse_heap.MinKey();
while ((forward_heap_min + reverse_heap_min <= weight) &&
(forward_heap.Size() + reverse_heap.Size() > 0))
{
progress = false;
if (!forward_heap.Empty() && (forward_heap.MinKey() < forward_search_radius))
if (!forward_heap.Empty())
{
progress = true;
routingStep<FORWARD_DIRECTION>(facade,
partition,
cells,
forward_heap,
reverse_heap,
parent_cell,
middle,
weight,
forward_search_radius,
reverse_search_radius);
forward_heap_min = forward_heap.MinKey();
routingStep<FORWARD_DIRECTION>(
facade, partition, cells, forward_heap, reverse_heap, parent_cell, middle, weight);
}
if (!reverse_heap.Empty() && (reverse_heap.MinKey() < reverse_search_radius))
if (!reverse_heap.Empty())
{
progress = true;
routingStep<REVERSE_DIRECTION>(facade,
partition,
cells,
reverse_heap,
forward_heap,
parent_cell,
middle,
weight,
reverse_search_radius,
forward_search_radius);
reverse_heap_min = reverse_heap.MinKey();
routingStep<REVERSE_DIRECTION>(
facade, partition, cells, reverse_heap, forward_heap, parent_cell, middle, weight);
}
} while (progress);
};

// No path found for both target nodes?
if (weight == INVALID_EDGE_WEIGHT || SPECIAL_NODEID == middle)
Expand Down

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