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Direct edges in contractor correctly and add better graph validation.

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This commit is contained in:
Patrick Niklaus
2015-05-24 17:25:38 +02:00
parent aba3ec692f
commit 2777d53a12
4 changed files with 232 additions and 233 deletions
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data_structures/node_based_graph.hpp
+114 -86
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@@ -74,7 +74,92 @@ struct NodeBasedEdgeData
using NodeBasedDynamicGraph = DynamicGraph<NodeBasedEdgeData>;
inline bool validateNeighborHood(const NodeBasedDynamicGraph& graph, const NodeID source)
{
for (auto edge = graph.BeginEdges(source); edge < graph.EndEdges(source); ++edge)
{
const auto& data = graph.GetEdgeData(edge);
if (!data.forward && !data.backward)
{
SimpleLogger().Write(logWARNING) << "Invalid edge directions";
return false;
}
auto target = graph.GetTarget(edge);
if (target == SPECIAL_NODEID)
{
SimpleLogger().Write(logWARNING) << "Invalid edge target";
return false;
}
bool found_reverse = false;
for (auto rev_edge = graph.BeginEdges(target); rev_edge < graph.EndEdges(target); ++rev_edge)
{
auto rev_target = graph.GetTarget(rev_edge);
if (rev_target == SPECIAL_NODEID)
{
SimpleLogger().Write(logWARNING) << "Invalid reverse edge target";
return false;
}
if (rev_target != source)
{
continue;
}
if (found_reverse)
{
SimpleLogger().Write(logWARNING) << "Found more than one reverse edge";
return false;
}
const auto& rev_data = graph.GetEdgeData(rev_edge);
// edge is incoming, this must be an outgoing edge
if (data.backward && !rev_data.forward)
{
SimpleLogger().Write(logWARNING) << "Found no outgoing edge to an incoming edge!";
return false;
}
// edge is bi-directional, reverse must be as well
if (data.forward && data.backward && (!rev_data.forward || !rev_data.backward))
{
SimpleLogger().Write(logWARNING) << "Found bi-directional edge that is not bi-directional to both ends";
return false;
}
found_reverse = true;
}
if (!found_reverse)
{
SimpleLogger().Write(logWARNING) << "Could not find reverse edge";
return false;
}
}
return true;
}
// This function checks if the overal graph is undirected (has an edge in each direction).
inline bool validateNodeBasedGraph(const NodeBasedDynamicGraph& graph)
{
for (auto source = 0u; source < graph.GetNumberOfNodes(); ++source)
{
if (!validateNeighborHood(graph, source))
{
return false;
}
}
return true;
}
// Factory method to create NodeBasedDynamicGraph from NodeBasedEdges
// The since DynamicGraph expects directed edges, we need to insert
// two edges for undirected edges.
inline std::shared_ptr<NodeBasedDynamicGraph>
NodeBasedDynamicGraphFromImportEdges(int number_of_nodes, std::vector<NodeBasedEdge> &input_edge_list)
{
@@ -83,9 +168,27 @@ NodeBasedDynamicGraphFromImportEdges(int number_of_nodes, std::vector<NodeBasedE
DeallocatingVector<NodeBasedDynamicGraph::InputEdge> edges_list;
NodeBasedDynamicGraph::InputEdge edge;
// Since DynamicGraph assumes directed edges we have to make sure we transformed
// the compressed edge format into single directed edges. We do this to make sure
// every node also knows its incoming edges, not only its outgoing edges and use the backward=true
// flag to indicate which is which.
//
// We do the transformation in the following way:
//
// if the edge (a, b) is split:
// 1. this edge must be in only one direction, so its a --> b
// 2. there must be another directed edge b --> a somewhere in the data
// if the edge (a, b) is not split:
// 1. this edge be on of a --> b od a <-> b
// (a <-- b gets reducted to b --> a)
// 2. a --> b will be transformed to a --> b and b <-- a
// 3. a <-> b will be transformed to a <-> b and b <-> a (I think a --> b and b <-- a would work as well though)
for (const NodeBasedEdge &import_edge : input_edge_list)
{
BOOST_ASSERT(import_edge.forward || import_edge.backward);
// edges that are not forward get converted by flipping the end points
BOOST_ASSERT(import_edge.forward);
if (import_edge.forward)
{
edge.source = import_edge.source;
@@ -93,20 +196,10 @@ NodeBasedDynamicGraphFromImportEdges(int number_of_nodes, std::vector<NodeBasedE
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;
}
BOOST_ASSERT(edge.source != edge.target);
edge.data.distance = (std::max)(static_cast<int>(import_edge.weight), 1);
edge.data.distance = static_cast<int>(import_edge.weight);
BOOST_ASSERT(edge.data.distance > 0);
edge.data.shortcut = false;
edge.data.roundabout = import_edge.roundabout;
@@ -126,82 +219,17 @@ NodeBasedDynamicGraphFromImportEdges(int number_of_nodes, std::vector<NodeBasedE
}
}
// 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>(
auto graph = std::make_shared<NodeBasedDynamicGraph>(
static_cast<NodeBasedDynamicGraph::NodeIterator>(number_of_nodes), edges_list);
#ifndef NDEBUG
BOOST_ASSERT(validateNodeBasedGraph(*graph));
#endif
return graph;
}
#endif // NODE_BASED_GRAPH_HPP