lemon-main: comparison lemon/suurballe.h

equal deleted inserted replaced

-:b7f2f856ffb2
+:2f1b555e9812
 ///\file
 ///\brief An algorithm for finding arc-disjoint paths between two
 /// nodes having minimum total length.
 #include <vector>
+#include <limits>
 #include <lemon/bin_heap.h>
 #include <lemon/path.h>
 #include <lemon/list_graph.h>
 #include <lemon/maps.h>
 ///
 /// \ref lemon::Suurballe "Suurballe" implements an algorithm for
 /// finding arc-disjoint paths having minimum total length (cost)
 /// from a given source node to a given target node in a digraph.
 ///
-/// In fact, this implementation is the specialization of the
+/// Note that this problem is a special case of the \ref min_cost_flow
-/// \ref CapacityScaling "successive shortest path" algorithm.
+/// "minimum cost flow problem". This implementation is actually an
+/// efficient specialized version of the \ref CapacityScaling
+/// "Successive Shortest Path" algorithm directly for this problem.
+/// Therefore this class provides query functions for flow values and
+/// node potentials (the dual solution) just like the minimum cost flow
+/// algorithms.
 ///
 /// \tparam GR The digraph type the algorithm runs on.
-/// The default value is \c ListDigraph.
+/// \tparam LEN The type of the length map.
-/// \tparam LEN The type of the length (cost) map.
+/// The default value is <tt>GR::ArcMap<int></tt>.
-/// The default value is <tt>Digraph::ArcMap<int></tt>.
 ///
 /// \warning Length values should be \e non-negative \e integers.
 ///
 /// \note For finding node-disjoint paths this algorithm can be used
-/// with \ref SplitNodes.
+/// along with the \ref SplitNodes adaptor.
 #ifdef DOXYGEN
 template <typename GR, typename LEN>
 #else
-template < typename GR = ListDigraph,
+template < typename GR,
 typename LEN = typename GR::template ArcMap<int> >
 #endif
 class Suurballe
 {
 TEMPLATE_DIGRAPH_TYPEDEFS(GR);
 typedef GR Digraph;
 /// The type of the length map.
 typedef LEN LengthMap;
 /// The type of the lengths.
 typedef typename LengthMap::Value Length;
+#ifdef DOXYGEN
+/// The type of the flow map.
+typedef GR::ArcMap<int> FlowMap;
+/// The type of the potential map.
+typedef GR::NodeMap<Length> PotentialMap;
+#else
 /// The type of the flow map.
 typedef typename Digraph::template ArcMap<int> FlowMap;
 /// The type of the potential map.
 typedef typename Digraph::template NodeMap<Length> PotentialMap;
+#endif
 /// The type of the path structures.
-typedef SimplePath<Digraph> Path;
+typedef SimplePath<GR> Path;
 private:
-/// \brief Special implementation of the Dijkstra algorithm
+// ResidualDijkstra is a special implementation of the
-/// for finding shortest paths in the residual network.
+// Dijkstra algorithm for finding shortest paths in the
-///
+// residual network with respect to the reduced arc lengths
-/// \ref ResidualDijkstra is a special implementation of the
+// and modifying the node potentials according to the
-/// \ref Dijkstra algorithm for finding shortest paths in the
+// distance of the nodes.
-/// residual network of the digraph with respect to the reduced arc
-/// lengths and modifying the node potentials according to the
-/// distance of the nodes.
 class ResidualDijkstra
 {
 typedef typename Digraph::template NodeMap<int> HeapCrossRef;
 typedef BinHeap<Length, HeapCrossRef> Heap;
 Node _t;
 public:
 /// Constructor.
-ResidualDijkstra( const Digraph &digraph,
+ResidualDijkstra( const Digraph &graph,
 const FlowMap &flow,
 const LengthMap &length,
 PotentialMap &potential,
 PredMap &pred,
 Node s, Node t ) :
-_graph(digraph), _flow(flow), _length(length), _potential(potential),
+_graph(graph), _flow(flow), _length(length), _potential(potential),
-_dist(digraph), _pred(pred), _s(s), _t(t) {}
+_dist(graph), _pred(pred), _s(s), _t(t) {}
 /// \brief Run the algorithm. It returns \c true if a path is found
 /// from the source node to the target node.
 bool run() {
 HeapCrossRef heap_cross_ref(_graph, Heap::PRE_HEAP);
 /// \brief Constructor.
 ///
 /// Constructor.
 ///
-/// \param digraph The digraph the algorithm runs on.
+/// \param graph The digraph the algorithm runs on.
 /// \param length The length (cost) values of the arcs.
-/// \param s The source node.
+Suurballe( const Digraph &graph,
-/// \param t The target node.
+const LengthMap &length ) :
-Suurballe( const Digraph &digraph,
+_graph(graph), _length(length), _flow(0), _local_flow(false),
-const LengthMap &length,
+_potential(0), _local_potential(false), _pred(graph)
-Node s, Node t ) :
+{
-_graph(digraph), _length(length), _flow(0), _local_flow(false),
+LEMON_ASSERT(std::numeric_limits<Length>::is_integer,
-_potential(0), _local_potential(false), _source(s), _target(t),
+"The length type of Suurballe must be integer");
-_pred(digraph) {}
+}
 /// Destructor.
 ~Suurballe() {
 if (_local_flow) delete _flow;
 if (_local_potential) delete _potential;
 }
 /// \brief Set the flow map.
 ///
 /// This function sets the flow map.
-///
+/// If it is not used before calling \ref run() or \ref init(),
-/// The found flow contains only 0 and 1 values. It is the union of
+/// an instance will be allocated automatically. The destructor
-/// the found arc-disjoint paths.
+/// deallocates this automatically allocated map, of course.
+///
+/// The found flow contains only 0 and 1 values, since it is the
+/// union of the found arc-disjoint paths.
 ///
 /// \return <tt>(*this)</tt>
 Suurballe& flowMap(FlowMap &map) {
 if (_local_flow) {
 delete _flow;
 }
 /// \brief Set the potential map.
 ///
 /// This function sets the potential map.
-///
+/// If it is not used before calling \ref run() or \ref init(),
-/// The potentials provide the dual solution of the underlying
+/// an instance will be allocated automatically. The destructor
-/// minimum cost flow problem.
+/// deallocates this automatically allocated map, of course.
+///
+/// The node potentials provide the dual solution of the underlying
+/// \ref min_cost_flow "minimum cost flow problem".
 ///
 /// \return <tt>(*this)</tt>
 Suurballe& potentialMap(PotentialMap &map) {
 if (_local_potential) {
 delete _potential;
 /// \brief Run the algorithm.
 ///
 /// This function runs the algorithm.
 ///
+/// \param s The source node.
+/// \param t The target node.
 /// \param k The number of paths to be found.
 ///
 /// \return \c k if there are at least \c k arc-disjoint paths from
 /// \c s to \c t in the digraph. Otherwise it returns the number of
 /// arc-disjoint paths found.
 ///
-/// \note Apart from the return value, <tt>s.run(k)</tt> is just a
+/// \note Apart from the return value, <tt>s.run(s, t, k)</tt> is
-/// shortcut of the following code.
+/// just a shortcut of the following code.
 /// \code
-///   s.init();
+///   s.init(s);
-///   s.findFlow(k);
+///   s.findFlow(t, k);
 ///   s.findPaths();
 /// \endcode
-int run(int k = 2) {
+int run(const Node& s, const Node& t, int k = 2) {
-init();
+init(s);
-findFlow(k);
+findFlow(t, k);
 findPaths();
 return _path_num;
 }
 /// \brief Initialize the algorithm.
 ///
 /// This function initializes the algorithm.
-void init() {
+///
+/// \param s The source node.
+void init(const Node& s) {
+_source = s;
 // Initialize maps
 if (!_flow) {
 _flow = new FlowMap(_graph);
 _local_flow = true;
 }
 _potential = new PotentialMap(_graph);
 _local_potential = true;
 }
 for (ArcIt e(_graph); e != INVALID; ++e) (*_flow)[e] = 0;
 for (NodeIt n(_graph); n != INVALID; ++n) (*_potential)[n] = 0;
+}
-_dijkstra = new ResidualDijkstra( _graph, *_flow, _length,
-*_potential, _pred,
+/// \brief Execute the algorithm to find an optimal flow.
-_source, _target );
-}
-/// \brief Execute the successive shortest path algorithm to find
-/// an optimal flow.
 ///
 /// This function executes the successive shortest path algorithm to
-/// find a minimum cost flow, which is the union of \c k or less
+/// find a minimum cost flow, which is the union of \c k (or less)
 /// arc-disjoint paths.
 ///
+/// \param t The target node.
+/// \param k The number of paths to be found.
+///
 /// \return \c k if there are at least \c k arc-disjoint paths from
-/// \c s to \c t in the digraph. Otherwise it returns the number of
+/// the source node to the given node \c t in the digraph.
-/// arc-disjoint paths found.
+/// Otherwise it returns the number of arc-disjoint paths found.
 ///
 /// \pre \ref init() must be called before using this function.
-int findFlow(int k = 2) {
+int findFlow(const Node& t, int k = 2) {
+_target = t;
+_dijkstra =
+new ResidualDijkstra( _graph, *_flow, _length, *_potential, _pred,
+_source, _target );
 // Find shortest paths
 _path_num = 0;
 while (_path_num < k) {
 // Run Dijkstra
 if (!_dijkstra->run()) break;
 return _path_num;
 }
 /// \brief Compute the paths from the flow.
 ///
-/// This function computes the paths from the flow.
+/// This function computes the paths from the found minimum cost flow,
+/// which is the union of some arc-disjoint paths.
 ///
 /// \pre \ref init() and \ref findFlow() must be called before using
 /// this function.
 void findPaths() {
-// Create the residual flow map (the union of the paths not found
-// so far)
 FlowMap res_flow(_graph);
 for(ArcIt a(_graph); a != INVALID; ++a) res_flow[a] = (*_flow)[a];
 paths.clear();
 paths.resize(_path_num);
 /// functions.
 /// \n The algorithm should be executed before using them.
 /// @{
-/// \brief Return a const reference to the arc map storing the
+/// \brief Return the total length of the found paths.
-/// found flow.
+///
-///
+/// This function returns the total length of the found paths, i.e.
-/// This function returns a const reference to the arc map storing
+/// the total cost of the found flow.
-/// the flow that is the union of the found arc-disjoint paths.
+/// The complexity of the function is O(e).
-///
-/// \pre \ref run() or \ref findFlow() must be called before using
-/// this function.
-const FlowMap& flowMap() const {
-return *_flow;
-}
-/// \brief Return a const reference to the node map storing the
-/// found potentials (the dual solution).
-///
-/// This function returns a const reference to the node map storing
-/// the found potentials that provide the dual solution of the
-/// underlying minimum cost flow problem.
-///
-/// \pre \ref run() or \ref findFlow() must be called before using
-/// this function.
-const PotentialMap& potentialMap() const {
-return *_potential;
-}
-/// \brief Return the flow on the given arc.
-///
-/// This function returns the flow on the given arc.
-/// It is \c 1 if the arc is involved in one of the found paths,
-/// otherwise it is \c 0.
-///
-/// \pre \ref run() or \ref findFlow() must be called before using
-/// this function.
-int flow(const Arc& arc) const {
-return (*_flow)[arc];
-}
-/// \brief Return the potential of the given node.
-///
-/// This function returns the potential of the given node.
-///
-/// \pre \ref run() or \ref findFlow() must be called before using
-/// this function.
-Length potential(const Node& node) const {
-return (*_potential)[node];
-}
-/// \brief Return the total length (cost) of the found paths (flow).
-///
-/// This function returns the total length (cost) of the found paths
-/// (flow). The complexity of the function is O(e).
 ///
 /// \pre \ref run() or \ref findFlow() must be called before using
 /// this function.
 Length totalLength() const {
 Length c = 0;
 for (ArcIt e(_graph); e != INVALID; ++e)
 c += (*_flow)[e] * _length[e];
 return c;
 }
+/// \brief Return the flow value on the given arc.
+///
+/// This function returns the flow value on the given arc.
+/// It is \c 1 if the arc is involved in one of the found arc-disjoint
+/// paths, otherwise it is \c 0.
+///
+/// \pre \ref run() or \ref findFlow() must be called before using
+/// this function.
+int flow(const Arc& arc) const {
+return (*_flow)[arc];
+}
+/// \brief Return a const reference to an arc map storing the
+/// found flow.
+///
+/// This function returns a const reference to an arc map storing
+/// the flow that is the union of the found arc-disjoint paths.
+///
+/// \pre \ref run() or \ref findFlow() must be called before using
+/// this function.
+const FlowMap& flowMap() const {
+return *_flow;
+}
+/// \brief Return the potential of the given node.
+///
+/// This function returns the potential of the given node.
+/// The node potentials provide the dual solution of the
+/// underlying \ref min_cost_flow "minimum cost flow problem".
+///
+/// \pre \ref run() or \ref findFlow() must be called before using
+/// this function.
+Length potential(const Node& node) const {
+return (*_potential)[node];
+}
+/// \brief Return a const reference to a node map storing the
+/// found potentials (the dual solution).
+///
+/// This function returns a const reference to a node map storing
+/// the found potentials that provide the dual solution of the
+/// underlying \ref min_cost_flow "minimum cost flow problem".
+///
+/// \pre \ref run() or \ref findFlow() must be called before using
+/// this function.
+const PotentialMap& potentialMap() const {
+return *_potential;
+}
 /// \brief Return the number of the found paths.
 ///
 /// This function returns the number of the found paths.
 ///
 /// \pre \ref run() or \ref findFlow() must be called before using
 /// \brief Return a const reference to the specified path.
 ///
 /// This function returns a const reference to the specified path.
 ///
-/// \param i The function returns the \c i-th path.
+/// \param i The function returns the <tt>i</tt>-th path.
 /// \c i must be between \c 0 and <tt>%pathNum()-1</tt>.
 ///
 /// \pre \ref run() or \ref findPaths() must be called before using
 /// this function.
 Path path(int i) const {

changeset 756	53bea38f71cb
parent 584	33c6b6e755cd
child 851	c67e235c832f