LEMON/LEMON-official Changeset - r910:9a7e4e606f83

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Changeset - r910:9a7e4e606f83

« 909:ec0b1b

946:5df6a8 »

r910:9a7e4e606f83

Fri, 16 Oct 2009 02:32:30

[Not Reviewed]

0 comments (0 inline)

kpeter (Peter Kovacs)
kpeter@inf.elte.hu

Add a fullInit() function to Suurballe (#181, #323) to provide faster handling of multiple targets. A start() function is also added, just for the sake of convenience.

0 2 0

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2 files changed with 104 insertions and 15 deletions:

lemon/suurballe.h

101

test/suurballe_test.cc

↑ Collapse diff ↑

lemon/suurballe.h

Show inline comments

@@ -26,12 +26,13 @@
 		#include <vector>
 		#include <limits>
 		#include <lemon/bin_heap.h>
 		#include <lemon/path.h>
 		#include <lemon/list_graph.h>
 		#include <lemon/dijkstra.h>
 		#include <lemon/maps.h>
 		namespace lemon {
 		  /// \addtogroup shortest_path
 		  /// @{
@@ -94,22 +95,22 @@
 		    /// The type of the path structures.
 		    typedef SimplePath<GR> Path;
 		  private:
 		    typedef typename Digraph::template NodeMap<int> HeapCrossRef;
 		    typedef BinHeap<Length, HeapCrossRef> Heap;
 		    // ResidualDijkstra is a special implementation of the
 		    // Dijkstra algorithm for finding shortest paths in the
 		    // residual network 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;
 		    private:
 		      const Digraph &_graph;
 		      const LengthMap &_length;
 		      const FlowMap &_flow;
 		      PotentialMap &_pi;
@@ -276,30 +277,38 @@
 		    std::vector<Path> _paths;
 		    int _path_num;
 		    // The pred arc map
 		    PredMap _pred;
 		    // Data for full init
 		    PotentialMap *_init_dist;
 		    PredMap *_init_pred;
 		    bool _full_init;
 		  public:
 		    /// \brief Constructor.
 		    ///
 		    /// Constructor.
 		    ///
 		    /// \param graph The digraph the algorithm runs on.
 		    /// \param length The length (cost) values of the arcs.
 		    Suurballe( const Digraph &graph,
 		               const LengthMap &length ) :
 		      _graph(graph), _length(length), _flow(0), _local_flow(false),
 		      _potential(0), _local_potential(false), _pred(graph)
+		      _potential(0), _local_potential(false), _pred(graph),
 		      _init_dist(0), _init_pred(0)
 		    {}
 		    /// Destructor.
 		    ~Suurballe() {
 		      if (_local_flow) delete _flow;
 		      if (_local_potential) delete _potential;
 		      delete _init_dist;
 		      delete _init_pred;
+		    }
 		    /// \brief Set the flow map.
 		    ///
 		    /// This function sets the flow map.
 		    /// If it is not used before calling \ref run() or \ref init(),
@@ -338,16 +347,19 @@
 		      _potential = &map;
 		      return *this;
+		    }
 		    /// \name Execution Control
 		    /// The simplest way to execute the algorithm is to call the run()
 		    /// function.
 		    /// \n
 		    /// function.\n
 		    /// If you need to execute the algorithm many times using the same
 		    /// source node, then you may call fullInit() once and start()
 		    /// for each target node.\n
 		    /// If you only need the flow that is the union of the found
-		    /// arc-disjoint paths, you may call init() and findFlow().
+		    /// arc-disjoint paths, then you may call findFlow() instead of
 		    /// start().
 		    /// @{
 		    /// \brief Run the algorithm.
 		    ///
 		    /// This function runs the algorithm.
@@ -361,25 +373,23 @@
 		    /// arc-disjoint paths found.
 		    ///
 		    /// \note Apart from the return value, <tt>s.run(s, t, k)</tt> is
 		    /// just a shortcut of the following code.
 		    /// \code
 		    ///   s.init(s);
 		    ///   s.findFlow(t, k);
 		    ///   s.findPaths();
 		    ///   s.start(t, k);
 		    /// \endcode
 		    int run(const Node& s, const Node& t, int k = 2) {
 		      init(s);
 		      findFlow(t, k);
 		      findPaths();
 		      start(t, k);
 		      return _path_num;
+		    }
 		    /// \brief Initialize the algorithm.
 		    ///
 		    /// This function initializes the algorithm.
+		    /// This function initializes the algorithm with the given source node.
 		    ///
 		    /// \param s The source node.
 		    void init(const Node& s) {
 		      _s = s;
 		      // Initialize maps
@@ -388,14 +398,69 @@
 		        _local_flow = true;
+		      }
 		      if (!_potential) {
 		        _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;
 		      _full_init = false;
+		    }
 		    /// \brief Initialize the algorithm and perform Dijkstra.
 		    ///
 		    /// This function initializes the algorithm and performs a full
 		    /// Dijkstra search from the given source node. It makes consecutive
 		    /// executions of \ref start() "start(t, k)" faster, since they
 		    /// have to perform %Dijkstra only k-1 times.
 		    ///
 		    /// This initialization is usually worth using instead of \ref init()
 		    /// if the algorithm is executed many times using the same source node.
 		    ///
 		    /// \param s The source node.
 		    void fullInit(const Node& s) {
 		      // Initialize maps
 		      init(s);
 		      if (!_init_dist) {
 		        _init_dist = new PotentialMap(_graph);
+		      }
 		      if (!_init_pred) {
 		        _init_pred = new PredMap(_graph);
+		      }
 		      // Run a full Dijkstra
 		      typename Dijkstra<Digraph, LengthMap>
 		        ::template SetStandardHeap<Heap>
 		        ::template SetDistMap<PotentialMap>
 		        ::template SetPredMap<PredMap>
 		        ::Create dijk(_graph, _length);
 		      dijk.distMap(*_init_dist).predMap(*_init_pred);
 		      dijk.run(s);
 		      _full_init = true;
+		    }
 		    /// \brief Execute the algorithm.
 		    ///
 		    /// This function executes the algorithm.
 		    ///
 		    /// \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.start(t, k)</tt> is
 		    /// just a shortcut of the following code.
 		    /// \code
 		    ///   s.findFlow(t, k);
 		    ///   s.findPaths();
 		    /// \endcode
 		    int start(const Node& t, int k = 2) {
 		      findFlow(t, k);
 		      findPaths();
 		      return _path_num;
+		    }
 		    /// \brief Execute the 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)
@@ -410,14 +475,35 @@
 		    ///
 		    /// \pre \ref init() must be called before using this function.
 		    int findFlow(const Node& t, int k = 2) {
 		      _t = t;
 		      ResidualDijkstra dijkstra(*this);
 		      // Initialization
 		      for (ArcIt e(_graph); e != INVALID; ++e) {
 		        (*_flow)[e] = 0;
+		      }
 		      if (_full_init) {
 		        for (NodeIt n(_graph); n != INVALID; ++n) {
 		          (*_potential)[n] = (*_init_dist)[n];
+		        }
 		        Node u = _t;
 		        Arc e;
 		        while ((e = (*_init_pred)[u]) != INVALID) {
 		          (*_flow)[e] = 1;
 		          u = _graph.source(e);
+		        }
 		        _path_num = 1;
 		      } else {
 		        for (NodeIt n(_graph); n != INVALID; ++n) {
 		          (*_potential)[n] = 0;
+		        }
 		        _path_num = 0;
+		      }
 		      // Find shortest paths
 		      _path_num = 0;
 		      while (_path_num < k) {
 		        // Run Dijkstra
 		        if (!dijkstra.run(_path_num)) break;
 		        ++_path_num;
 		        // Set the flow along the found shortest path

test/suurballe_test.cc

Show inline comments

@@ -98,12 +98,15 @@
 		    .potentialMap(pi);
 		  int k;
 		  k = suurb_test.run(n, n);
 		  k = suurb_test.run(n, n, k);
 		  suurb_test.init(n);
 		  suurb_test.fullInit(n);
 		  suurb_test.start(n);
 		  suurb_test.start(n, k);
 		  k = suurb_test.findFlow(n);
 		  k = suurb_test.findFlow(n, k);
 		  suurb_test.findPaths();
 		  int f;
 		  VType c;

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