max/edmonds-matching-algorithm
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update ρ correctly: include verticse that were contracted to paths

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Maximilian Keßler 2023-11-05 18:37:29 +01:00
parent 249877af7e
commit a102845ba5
Signed by: max
GPG key ID: BCC5A619923C0BA5
1 changed files with 16 additions and 5 deletions
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21
src/edmonds.cpp
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@ -103,10 +103,10 @@ void maximum_matching_from_initial_matching(Graph & graph)
for(NodeId neighbor_id : graph.node(id).neighbors()) for(NodeId neighbor_id : graph.node(id).neighbors())
{ {
check_integrity(graph); check_integrity(graph);
std::cout << "Check passed" << std::endl; //std::cout << "Check passed" << std::endl;
if (graph.is_out_of_forest(neighbor_id)) if (graph.is_out_of_forest(neighbor_id))
{ {
std::cout << "Grow forest" << std::endl; //std::cout << "Grow forest" << std::endl;
// Grow Forest // Grow Forest
graph.node(neighbor_id).phi = id; graph.node(neighbor_id).phi = id;
} }
@ -117,7 +117,7 @@ void maximum_matching_from_initial_matching(Graph & graph)
if (x_path.back() != y_path.back()) if (x_path.back() != y_path.back())
{ {
std::cout << "Augment" << std::endl; //std::cout << "Augment" << std::endl;
// Paths are disjoint -> augment // Paths are disjoint -> augment
graph.node(x_path.front()).matched_neighbor = y_path.front(); graph.node(x_path.front()).matched_neighbor = y_path.front();
graph.node(y_path.front()).matched_neighbor = x_path.front(); graph.node(y_path.front()).matched_neighbor = x_path.front();
@ -140,7 +140,7 @@ void maximum_matching_from_initial_matching(Graph & graph)
} }
else else
{ {
std::cout << "Contract blossom" << std::endl; //std::cout << "Contract blossom" << std::endl;
// Paths are not disjoint -> shrink blossom // Paths are not disjoint -> shrink blossom
size_t distance_from_x = x_path.size() - 1; size_t distance_from_x = x_path.size() - 1;
size_t distance_from_y = y_path.size() - 1; size_t distance_from_y = y_path.size() - 1;
@ -181,7 +181,10 @@ void maximum_matching_from_initial_matching(Graph & graph)
graph.node(y_path.front()).phi = x_path.front(); graph.node(y_path.front()).phi = x_path.front();
} }
// Update root indices // Update root indices. We have to do this for all vertices v with
// ρ(v) in the paths from x or y to r
// We update ρ(v) first for the paths themselves, and then 'contract' ρ
// by updating ρ(v) to r for all vertices where ρ(ρ(v)) = r
for(size_t i = 0; i <= distance_from_x; ++i) for(size_t i = 0; i <= distance_from_x; ++i)
{ {
graph.node(x_path[i]).rho = blossom_root_id; graph.node(x_path[i]).rho = blossom_root_id;
@ -190,6 +193,14 @@ void maximum_matching_from_initial_matching(Graph & graph)
{ {
graph.node(y_path[i]).rho = blossom_root_id; graph.node(y_path[i]).rho = blossom_root_id;
} }
for(NodeId node_id = 0; node_id < graph.num_nodes(); ++node_id)
{
if (graph.rho(graph.rho(node_id)) == blossom_root_id)
{
graph.node(node_id).rho = blossom_root_id;
}
}
check_integrity(graph);
} }
} }
} }