This class implements Edmonds' alternating forest matching algorithm for finding a maximum cardinality matching in a general undirected graph. It can be started from an arbitrary initial matching (the default is the empty one).
The dual solution of the problem is a map of the nodes to Status, having values EVEN (or D), ODD (or A) and MATCHED (or C) defining the Gallai-Edmonds decomposition of the graph. The nodes in EVEN/D induce a subgraph with factor-critical components, the nodes in ODD/A form the canonical barrier, and the nodes in MATCHED/C induce a graph having a perfect matching. The number of the factor-critical components minus the number of barrier nodes is a lower bound on the unmatched nodes, and the matching is optimal if and only if this bound is tight. This decomposition can be obtained using status() or statusMap() after running the algorithm.
| GR | The undirected graph type the algorithm runs on. |
#include <lemon/matching.h>
Public Types | |
| enum | Status { EVEN = 1 , MATCHED = 0 , ODD = -1 , UNMATCHED = -2 } |
Status constants for Gallai-Edmonds decomposition. More... | |
| typedef GR | Graph |
| The graph type of the algorithm. | |
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typedef Graph::template NodeMap< typename Graph::Arc > | MatchingMap |
| The type of the matching map. | |
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typedef Graph::template NodeMap< Status > | StatusMap |
| The type of the status map. | |
Public Member Functions | |
| MaxMatching (const Graph &graph) | |
Execution Control | |
The simplest way to execute the algorithm is to use the | |
| void | init () |
| Set the initial matching to the empty matching. | |
| void | greedyInit () |
| Find an initial matching in a greedy way. | |
| template<typename MatchingMap > | |
| bool | matchingInit (const MatchingMap &matching) |
| Initialize the matching from a map. | |
| void | startSparse () |
| Start Edmonds' algorithm. | |
| void | startDense () |
| Start Edmonds' algorithm with a heuristic improvement for dense graphs. | |
| void | run () |
| Run Edmonds' algorithm. | |
Primal Solution | |
Functions to get the primal solution, i.e. the maximum matching. | |
| int | matchingSize () const |
| Return the size (cardinality) of the matching. | |
| bool | matching (const Edge &edge) const |
Return true if the given edge is in the matching. | |
| Arc | matching (const Node &n) const |
| Return the matching arc (or edge) incident to the given node. | |
| const MatchingMap & | matchingMap () const |
| Return a const reference to the matching map. | |
| Node | mate (const Node &n) const |
| Return the mate of the given node. | |
Dual Solution | |
Functions to get the dual solution, i.e. the Gallai-Edmonds decomposition. | |
| Status | status (const Node &n) const |
| Return the status of the given node in the Edmonds-Gallai decomposition. | |
| const StatusMap & | statusMap () const |
| Return a const reference to the status map, which stores the Edmonds-Gallai decomposition. | |
| bool | barrier (const Node &n) const |
Return true if the given node is in the barrier. | |
| enum Status |
These constants are used for indicating the Gallai-Edmonds decomposition of a graph. The nodes with status EVEN (or D) induce a subgraph with factor-critical components, the nodes with status ODD (or A) form the canonical barrier, and the nodes with status MATCHED (or C) induce a subgraph having a perfect matching.
| MaxMatching | ( | const Graph & | graph | ) | [inline] |
Constructor.
| void init | ( | ) | [inline] |
This function sets the initial matching to the empty matching.
| void greedyInit | ( | ) | [inline] |
This function finds an initial matching in a greedy way.
| bool matchingInit | ( | const MatchingMap & | matching | ) | [inline] |
This function initializes the matching from a bool valued edge map. This map should have the property that there are no two incident edges with true value, i.e. it really contains a matching.
true if the map contains a matching. | void startSparse | ( | ) | [inline] |
This function runs the original Edmonds' algorithm.
| void startDense | ( | ) | [inline] |
This function runs Edmonds' algorithm with a heuristic of postponing shrinks, therefore resulting in a faster algorithm for dense graphs.
| void run | ( | ) | [inline] |
This function runs Edmonds' algorithm. An additional heuristic of postponing shrinks is used for relatively dense graphs (for which m>=2*n holds).
| int matchingSize | ( | ) | const [inline] |
This function returns the size (cardinality) of the current matching. After run() it returns the size of the maximum matching in the graph.
| bool matching | ( | const Edge & | edge | ) | const [inline] |
This function returns true if the given edge is in the current matching.
| Arc matching | ( | const Node & | n | ) | const [inline] |
This function returns the matching arc (or edge) incident to the given node in the current matching or INVALID if the node is not covered by the matching.
| const MatchingMap& matchingMap | ( | ) | const [inline] |
This function returns a const reference to a node map that stores the matching arc (or edge) incident to each node.
| Node mate | ( | const Node & | n | ) | const [inline] |
This function returns the mate of the given node in the current matching or INVALID if the node is not covered by the matching.
| Status status | ( | const Node & | n | ) | const [inline] |
This function returns the status of the given node in the Edmonds-Gallai decomposition.
| const StatusMap& statusMap | ( | ) | const [inline] |
This function returns a const reference to a node map that stores the status of each node in the Edmonds-Gallai decomposition.
| bool barrier | ( | const Node & | n | ) | const [inline] |
This function returns true if the given node is in the barrier.
1.7.3