1.1 --- a/lemon/belmann_ford.h Tue Jan 03 14:56:45 2006 +0000
1.2 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000
1.3 @@ -1,950 +0,0 @@
1.4 -/* -*- C++ -*-
1.5 - * lemon/belmann_ford.h - Part of LEMON, a generic C++ optimization library
1.6 - *
1.7 - * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
1.8 - * (Egervary Research Group on Combinatorial Optimization, EGRES).
1.9 - *
1.10 - * Permission to use, modify and distribute this software is granted
1.11 - * provided that this copyright notice appears in all copies. For
1.12 - * precise terms see the accompanying LICENSE file.
1.13 - *
1.14 - * This software is provided "AS IS" with no warranty of any kind,
1.15 - * express or implied, and with no claim as to its suitability for any
1.16 - * purpose.
1.17 - *
1.18 - */
1.19 -
1.20 -#ifndef LEMON_BELMANN_FORD_H
1.21 -#define LEMON_BELMANN_FORD_H
1.22 -
1.23 -/// \ingroup flowalgs
1.24 -/// \file
1.25 -/// \brief BelmannFord algorithm.
1.26 -///
1.27 -
1.28 -#include <lemon/list_graph.h>
1.29 -#include <lemon/invalid.h>
1.30 -#include <lemon/error.h>
1.31 -#include <lemon/maps.h>
1.32 -
1.33 -#include <limits>
1.34 -
1.35 -namespace lemon {
1.36 -
1.37 - /// \brief Default OperationTraits for the BelmannFord algorithm class.
1.38 - ///
1.39 - /// It defines all computational operations and constants which are
1.40 - /// used in the belmann ford algorithm. The default implementation
1.41 - /// is based on the numeric_limits class. If the numeric type does not
1.42 - /// have infinity value then the maximum value is used as extremal
1.43 - /// infinity value.
1.44 - template <
1.45 - typename Value,
1.46 - bool has_infinity = std::numeric_limits<Value>::has_infinity>
1.47 - struct BelmannFordDefaultOperationTraits {
1.48 - /// \brief Gives back the zero value of the type.
1.49 - static Value zero() {
1.50 - return static_cast<Value>(0);
1.51 - }
1.52 - /// \brief Gives back the positive infinity value of the type.
1.53 - static Value infinity() {
1.54 - return std::numeric_limits<Value>::infinity();
1.55 - }
1.56 - /// \brief Gives back the sum of the given two elements.
1.57 - static Value plus(const Value& left, const Value& right) {
1.58 - return left + right;
1.59 - }
1.60 - /// \brief Gives back true only if the first value less than the second.
1.61 - static bool less(const Value& left, const Value& right) {
1.62 - return left < right;
1.63 - }
1.64 - };
1.65 -
1.66 - template <typename Value>
1.67 - struct BelmannFordDefaultOperationTraits<Value, false> {
1.68 - static Value zero() {
1.69 - return static_cast<Value>(0);
1.70 - }
1.71 - static Value infinity() {
1.72 - return std::numeric_limits<Value>::max();
1.73 - }
1.74 - static Value plus(const Value& left, const Value& right) {
1.75 - if (left == infinity() || right == infinity()) return infinity();
1.76 - return left + right;
1.77 - }
1.78 - static bool less(const Value& left, const Value& right) {
1.79 - return left < right;
1.80 - }
1.81 - };
1.82 -
1.83 - /// \brief Default traits class of BelmannFord class.
1.84 - ///
1.85 - /// Default traits class of BelmannFord class.
1.86 - /// \param _Graph Graph type.
1.87 - /// \param _LegthMap Type of length map.
1.88 - template<class _Graph, class _LengthMap>
1.89 - struct BelmannFordDefaultTraits {
1.90 - /// The graph type the algorithm runs on.
1.91 - typedef _Graph Graph;
1.92 -
1.93 - /// \brief The type of the map that stores the edge lengths.
1.94 - ///
1.95 - /// The type of the map that stores the edge lengths.
1.96 - /// It must meet the \ref concept::ReadMap "ReadMap" concept.
1.97 - typedef _LengthMap LengthMap;
1.98 -
1.99 - // The type of the length of the edges.
1.100 - typedef typename _LengthMap::Value Value;
1.101 -
1.102 - /// \brief Operation traits for belmann-ford algorithm.
1.103 - ///
1.104 - /// It defines the infinity type on the given Value type
1.105 - /// and the used operation.
1.106 - /// \see BelmannFordDefaultOperationTraits
1.107 - typedef BelmannFordDefaultOperationTraits<Value> OperationTraits;
1.108 -
1.109 - /// \brief The type of the map that stores the last edges of the
1.110 - /// shortest paths.
1.111 - ///
1.112 - /// The type of the map that stores the last
1.113 - /// edges of the shortest paths.
1.114 - /// It must meet the \ref concept::WriteMap "WriteMap" concept.
1.115 - ///
1.116 - typedef typename Graph::template NodeMap<typename _Graph::Edge> PredMap;
1.117 -
1.118 - /// \brief Instantiates a PredMap.
1.119 - ///
1.120 - /// This function instantiates a \ref PredMap.
1.121 - /// \param graph is the graph, to which we would like to define the PredMap.
1.122 - static PredMap *createPredMap(const _Graph& graph) {
1.123 - return new PredMap(graph);
1.124 - }
1.125 -
1.126 - /// \brief The type of the map that stores the dists of the nodes.
1.127 - ///
1.128 - /// The type of the map that stores the dists of the nodes.
1.129 - /// It must meet the \ref concept::WriteMap "WriteMap" concept.
1.130 - ///
1.131 - typedef typename Graph::template NodeMap<typename _LengthMap::Value>
1.132 - DistMap;
1.133 -
1.134 - /// \brief Instantiates a DistMap.
1.135 - ///
1.136 - /// This function instantiates a \ref DistMap.
1.137 - /// \param graph is the graph, to which we would like to define the
1.138 - /// \ref DistMap
1.139 - static DistMap *createDistMap(const _Graph& graph) {
1.140 - return new DistMap(graph);
1.141 - }
1.142 -
1.143 - };
1.144 -
1.145 - /// \brief %BelmannFord algorithm class.
1.146 - ///
1.147 - /// \ingroup flowalgs
1.148 - /// This class provides an efficient implementation of \c Belmann-Ford
1.149 - /// algorithm. The edge lengths are passed to the algorithm using a
1.150 - /// \ref concept::ReadMap "ReadMap", so it is easy to change it to any
1.151 - /// kind of length.
1.152 - ///
1.153 - /// The Belmann-Ford algorithm solves the shortest path from one node
1.154 - /// problem when the edges can have negative length but the graph should
1.155 - /// not contain cycles with negative sum of length. If we can assume
1.156 - /// that all edge is non-negative in the graph then the dijkstra algorithm
1.157 - /// should be used rather.
1.158 - ///
1.159 - /// The complexity of the algorithm is O(n * e).
1.160 - ///
1.161 - /// The type of the length is determined by the
1.162 - /// \ref concept::ReadMap::Value "Value" of the length map.
1.163 - ///
1.164 - /// \param _Graph The graph type the algorithm runs on. The default value
1.165 - /// is \ref ListGraph. The value of _Graph is not used directly by
1.166 - /// BelmannFord, it is only passed to \ref BelmannFordDefaultTraits.
1.167 - /// \param _LengthMap This read-only EdgeMap determines the lengths of the
1.168 - /// edges. The default map type is \ref concept::StaticGraph::EdgeMap
1.169 - /// "Graph::EdgeMap<int>". The value of _LengthMap is not used directly
1.170 - /// by BelmannFord, it is only passed to \ref BelmannFordDefaultTraits.
1.171 - /// \param _Traits Traits class to set various data types used by the
1.172 - /// algorithm. The default traits class is \ref BelmannFordDefaultTraits
1.173 - /// "BelmannFordDefaultTraits<_Graph,_LengthMap>". See \ref
1.174 - /// BelmannFordDefaultTraits for the documentation of a BelmannFord traits
1.175 - /// class.
1.176 - ///
1.177 - /// \author Balazs Dezso
1.178 -
1.179 -#ifdef DOXYGEN
1.180 - template <typename _Graph, typename _LengthMap, typename _Traits>
1.181 -#else
1.182 - template <typename _Graph=ListGraph,
1.183 - typename _LengthMap=typename _Graph::template EdgeMap<int>,
1.184 - typename _Traits=BelmannFordDefaultTraits<_Graph,_LengthMap> >
1.185 -#endif
1.186 - class BelmannFord {
1.187 - public:
1.188 -
1.189 - /// \brief \ref Exception for uninitialized parameters.
1.190 - ///
1.191 - /// This error represents problems in the initialization
1.192 - /// of the parameters of the algorithms.
1.193 -
1.194 - class UninitializedParameter : public lemon::UninitializedParameter {
1.195 - public:
1.196 - virtual const char* exceptionName() const {
1.197 - return "lemon::BelmannFord::UninitializedParameter";
1.198 - }
1.199 - };
1.200 -
1.201 - typedef _Traits Traits;
1.202 - ///The type of the underlying graph.
1.203 - typedef typename _Traits::Graph Graph;
1.204 -
1.205 - typedef typename Graph::Node Node;
1.206 - typedef typename Graph::NodeIt NodeIt;
1.207 - typedef typename Graph::Edge Edge;
1.208 - typedef typename Graph::OutEdgeIt OutEdgeIt;
1.209 -
1.210 - /// \brief The type of the length of the edges.
1.211 - typedef typename _Traits::LengthMap::Value Value;
1.212 - /// \brief The type of the map that stores the edge lengths.
1.213 - typedef typename _Traits::LengthMap LengthMap;
1.214 - /// \brief The type of the map that stores the last
1.215 - /// edges of the shortest paths.
1.216 - typedef typename _Traits::PredMap PredMap;
1.217 - /// \brief The type of the map that stores the dists of the nodes.
1.218 - typedef typename _Traits::DistMap DistMap;
1.219 - /// \brief The operation traits.
1.220 - typedef typename _Traits::OperationTraits OperationTraits;
1.221 - private:
1.222 - /// Pointer to the underlying graph.
1.223 - const Graph *graph;
1.224 - /// Pointer to the length map
1.225 - const LengthMap *length;
1.226 - ///Pointer to the map of predecessors edges.
1.227 - PredMap *_pred;
1.228 - ///Indicates if \ref _pred is locally allocated (\c true) or not.
1.229 - bool local_pred;
1.230 - ///Pointer to the map of distances.
1.231 - DistMap *_dist;
1.232 - ///Indicates if \ref _dist is locally allocated (\c true) or not.
1.233 - bool local_dist;
1.234 -
1.235 - typedef typename Graph::template NodeMap<bool> MaskMap;
1.236 - MaskMap *_mask;
1.237 -
1.238 - std::vector<Node> _process;
1.239 -
1.240 - /// Creates the maps if necessary.
1.241 - void create_maps() {
1.242 - if(!_pred) {
1.243 - local_pred = true;
1.244 - _pred = Traits::createPredMap(*graph);
1.245 - }
1.246 - if(!_dist) {
1.247 - local_dist = true;
1.248 - _dist = Traits::createDistMap(*graph);
1.249 - }
1.250 - _mask = new MaskMap(*graph, false);
1.251 - }
1.252 -
1.253 - public :
1.254 -
1.255 - typedef BelmannFord Create;
1.256 -
1.257 - /// \name Named template parameters
1.258 -
1.259 - ///@{
1.260 -
1.261 - template <class T>
1.262 - struct DefPredMapTraits : public Traits {
1.263 - typedef T PredMap;
1.264 - static PredMap *createPredMap(const Graph&) {
1.265 - throw UninitializedParameter();
1.266 - }
1.267 - };
1.268 -
1.269 - /// \brief \ref named-templ-param "Named parameter" for setting PredMap
1.270 - /// type
1.271 - /// \ref named-templ-param "Named parameter" for setting PredMap type
1.272 - ///
1.273 - template <class T>
1.274 - struct DefPredMap
1.275 - : public BelmannFord< Graph, LengthMap, DefPredMapTraits<T> > {
1.276 - typedef BelmannFord< Graph, LengthMap, DefPredMapTraits<T> > Create;
1.277 - };
1.278 -
1.279 - template <class T>
1.280 - struct DefDistMapTraits : public Traits {
1.281 - typedef T DistMap;
1.282 - static DistMap *createDistMap(const Graph& graph) {
1.283 - throw UninitializedParameter();
1.284 - }
1.285 - };
1.286 -
1.287 - /// \brief \ref named-templ-param "Named parameter" for setting DistMap
1.288 - /// type
1.289 - ///
1.290 - /// \ref named-templ-param "Named parameter" for setting DistMap type
1.291 - ///
1.292 - template <class T>
1.293 - struct DefDistMap
1.294 - : public BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > {
1.295 - typedef BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > Create;
1.296 - };
1.297 -
1.298 - template <class T>
1.299 - struct DefOperationTraitsTraits : public Traits {
1.300 - typedef T OperationTraits;
1.301 - };
1.302 -
1.303 - /// \brief \ref named-templ-param "Named parameter" for setting
1.304 - /// OperationTraits type
1.305 - ///
1.306 - /// \ref named-templ-param "Named parameter" for setting OperationTraits
1.307 - /// type
1.308 - template <class T>
1.309 - struct DefOperationTraits
1.310 - : public BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> > {
1.311 - typedef BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> >
1.312 - Create;
1.313 - };
1.314 -
1.315 - ///@}
1.316 -
1.317 - protected:
1.318 -
1.319 - BelmannFord() {}
1.320 -
1.321 - public:
1.322 -
1.323 - /// \brief Constructor.
1.324 - ///
1.325 - /// \param _graph the graph the algorithm will run on.
1.326 - /// \param _length the length map used by the algorithm.
1.327 - BelmannFord(const Graph& _graph, const LengthMap& _length) :
1.328 - graph(&_graph), length(&_length),
1.329 - _pred(0), local_pred(false),
1.330 - _dist(0), local_dist(false) {}
1.331 -
1.332 - ///Destructor.
1.333 - ~BelmannFord() {
1.334 - if(local_pred) delete _pred;
1.335 - if(local_dist) delete _dist;
1.336 - delete _mask;
1.337 - }
1.338 -
1.339 - /// \brief Sets the length map.
1.340 - ///
1.341 - /// Sets the length map.
1.342 - /// \return \c (*this)
1.343 - BelmannFord &lengthMap(const LengthMap &m) {
1.344 - length = &m;
1.345 - return *this;
1.346 - }
1.347 -
1.348 - /// \brief Sets the map storing the predecessor edges.
1.349 - ///
1.350 - /// Sets the map storing the predecessor edges.
1.351 - /// If you don't use this function before calling \ref run(),
1.352 - /// it will allocate one. The destuctor deallocates this
1.353 - /// automatically allocated map, of course.
1.354 - /// \return \c (*this)
1.355 - BelmannFord &predMap(PredMap &m) {
1.356 - if(local_pred) {
1.357 - delete _pred;
1.358 - local_pred=false;
1.359 - }
1.360 - _pred = &m;
1.361 - return *this;
1.362 - }
1.363 -
1.364 - /// \brief Sets the map storing the distances calculated by the algorithm.
1.365 - ///
1.366 - /// Sets the map storing the distances calculated by the algorithm.
1.367 - /// If you don't use this function before calling \ref run(),
1.368 - /// it will allocate one. The destuctor deallocates this
1.369 - /// automatically allocated map, of course.
1.370 - /// \return \c (*this)
1.371 - BelmannFord &distMap(DistMap &m) {
1.372 - if(local_dist) {
1.373 - delete _dist;
1.374 - local_dist=false;
1.375 - }
1.376 - _dist = &m;
1.377 - return *this;
1.378 - }
1.379 -
1.380 - /// \name Execution control
1.381 - /// The simplest way to execute the algorithm is to use
1.382 - /// one of the member functions called \c run(...).
1.383 - /// \n
1.384 - /// If you need more control on the execution,
1.385 - /// first you must call \ref init(), then you can add several source nodes
1.386 - /// with \ref addSource().
1.387 - /// Finally \ref start() will perform the actual path
1.388 - /// computation.
1.389 -
1.390 - ///@{
1.391 -
1.392 - /// \brief Initializes the internal data structures.
1.393 - ///
1.394 - /// Initializes the internal data structures.
1.395 - void init(const Value value = OperationTraits::infinity()) {
1.396 - create_maps();
1.397 - for (NodeIt it(*graph); it != INVALID; ++it) {
1.398 - _pred->set(it, INVALID);
1.399 - _dist->set(it, value);
1.400 - }
1.401 - _process.clear();
1.402 - if (OperationTraits::less(value, OperationTraits::infinity())) {
1.403 - for (NodeIt it(*graph); it != INVALID; ++it) {
1.404 - _process.push_back(it);
1.405 - _mask->set(it, true);
1.406 - }
1.407 - }
1.408 - }
1.409 -
1.410 - /// \brief Adds a new source node.
1.411 - ///
1.412 - /// The optional second parameter is the initial distance of the node.
1.413 - /// It just sets the distance of the node to the given value.
1.414 - void addSource(Node source, Value dst = OperationTraits::zero()) {
1.415 - _dist->set(source, dst);
1.416 - if (!(*_mask)[source]) {
1.417 - _process.push_back(source);
1.418 - _mask->set(source, true);
1.419 - }
1.420 - }
1.421 -
1.422 - /// \brief Executes one round from the belmann ford algorithm.
1.423 - ///
1.424 - /// If the algoritm calculated the distances in the previous round
1.425 - /// strictly for all at most k length paths then it will calculate the
1.426 - /// distances strictly for all at most k + 1 length paths. With k
1.427 - /// iteration this function calculates the at most k length paths.
1.428 - /// \return %True when the algorithm have not found more shorter paths.
1.429 - bool processNextRound() {
1.430 - for (int i = 0; i < (int)_process.size(); ++i) {
1.431 - _mask->set(_process[i], false);
1.432 - }
1.433 - std::vector<Node> nextProcess;
1.434 - std::vector<Value> values(_process.size());
1.435 - for (int i = 0; i < (int)_process.size(); ++i) {
1.436 - values[i] = (*_dist)[_process[i]];
1.437 - }
1.438 - for (int i = 0; i < (int)_process.size(); ++i) {
1.439 - for (OutEdgeIt it(*graph, _process[i]); it != INVALID; ++it) {
1.440 - Node target = graph->target(it);
1.441 - Value relaxed = OperationTraits::plus(values[i], (*length)[it]);
1.442 - if (OperationTraits::less(relaxed, (*_dist)[target])) {
1.443 - _pred->set(target, it);
1.444 - _dist->set(target, relaxed);
1.445 - if (!(*_mask)[target]) {
1.446 - _mask->set(target, true);
1.447 - nextProcess.push_back(target);
1.448 - }
1.449 - }
1.450 - }
1.451 - }
1.452 - _process.swap(nextProcess);
1.453 - return _process.empty();
1.454 - }
1.455 -
1.456 - /// \brief Executes one weak round from the belmann ford algorithm.
1.457 - ///
1.458 - /// If the algorithm calculated the distances in the
1.459 - /// previous round at least for all at most k length paths then it will
1.460 - /// calculate the distances at least for all at most k + 1 length paths.
1.461 - /// This function does not make it possible to calculate strictly the
1.462 - /// at most k length minimal paths, this is why it is
1.463 - /// called just weak round.
1.464 - /// \return %True when the algorithm have not found more shorter paths.
1.465 - bool processNextWeakRound() {
1.466 - for (int i = 0; i < (int)_process.size(); ++i) {
1.467 - _mask->set(_process[i], false);
1.468 - }
1.469 - std::vector<Node> nextProcess;
1.470 - for (int i = 0; i < (int)_process.size(); ++i) {
1.471 - for (OutEdgeIt it(*graph, _process[i]); it != INVALID; ++it) {
1.472 - Node target = graph->target(it);
1.473 - Value relaxed =
1.474 - OperationTraits::plus((*_dist)[_process[i]], (*length)[it]);
1.475 - if (OperationTraits::less(relaxed, (*_dist)[target])) {
1.476 - _pred->set(target, it);
1.477 - _dist->set(target, relaxed);
1.478 - if (!(*_mask)[target]) {
1.479 - _mask->set(target, true);
1.480 - nextProcess.push_back(target);
1.481 - }
1.482 - }
1.483 - }
1.484 - }
1.485 - _process.swap(nextProcess);
1.486 - return _process.empty();
1.487 - }
1.488 -
1.489 - /// \brief Executes the algorithm.
1.490 - ///
1.491 - /// \pre init() must be called and at least one node should be added
1.492 - /// with addSource() before using this function.
1.493 - ///
1.494 - /// This method runs the %BelmannFord algorithm from the root node(s)
1.495 - /// in order to compute the shortest path to each node. The algorithm
1.496 - /// computes
1.497 - /// - The shortest path tree.
1.498 - /// - The distance of each node from the root(s).
1.499 - void start() {
1.500 - int num = countNodes(*graph) - 1;
1.501 - for (int i = 0; i < num; ++i) {
1.502 - if (processNextWeakRound()) break;
1.503 - }
1.504 - }
1.505 -
1.506 - /// \brief Executes the algorithm and checks the negative cycles.
1.507 - ///
1.508 - /// \pre init() must be called and at least one node should be added
1.509 - /// with addSource() before using this function. If there is
1.510 - /// a negative cycles in the graph it gives back false.
1.511 - ///
1.512 - /// This method runs the %BelmannFord algorithm from the root node(s)
1.513 - /// in order to compute the shortest path to each node. The algorithm
1.514 - /// computes
1.515 - /// - The shortest path tree.
1.516 - /// - The distance of each node from the root(s).
1.517 - bool checkedStart() {
1.518 - int num = countNodes(*graph);
1.519 - for (int i = 0; i < num; ++i) {
1.520 - if (processNextWeakRound()) return true;
1.521 - }
1.522 - return false;
1.523 - }
1.524 -
1.525 - /// \brief Executes the algorithm with path length limit.
1.526 - ///
1.527 - /// \pre init() must be called and at least one node should be added
1.528 - /// with addSource() before using this function.
1.529 - ///
1.530 - /// This method runs the %BelmannFord algorithm from the root node(s)
1.531 - /// in order to compute the shortest path with at most \c length edge
1.532 - /// long paths to each node. The algorithm computes
1.533 - /// - The shortest path tree.
1.534 - /// - The limited distance of each node from the root(s).
1.535 - void limitedStart(int length) {
1.536 - for (int i = 0; i < length; ++i) {
1.537 - if (processNextRound()) break;
1.538 - }
1.539 - }
1.540 -
1.541 - /// \brief Runs %BelmannFord algorithm from node \c s.
1.542 - ///
1.543 - /// This method runs the %BelmannFord algorithm from a root node \c s
1.544 - /// in order to compute the shortest path to each node. The algorithm
1.545 - /// computes
1.546 - /// - The shortest path tree.
1.547 - /// - The distance of each node from the root.
1.548 - ///
1.549 - /// \note d.run(s) is just a shortcut of the following code.
1.550 - /// \code
1.551 - /// d.init();
1.552 - /// d.addSource(s);
1.553 - /// d.start();
1.554 - /// \endcode
1.555 - void run(Node s) {
1.556 - init();
1.557 - addSource(s);
1.558 - start();
1.559 - }
1.560 -
1.561 - /// \brief Runs %BelmannFord algorithm with limited path length
1.562 - /// from node \c s.
1.563 - ///
1.564 - /// This method runs the %BelmannFord algorithm from a root node \c s
1.565 - /// in order to compute the shortest path with at most \c len edges
1.566 - /// to each node. The algorithm computes
1.567 - /// - The shortest path tree.
1.568 - /// - The distance of each node from the root.
1.569 - ///
1.570 - /// \note d.run(s, len) is just a shortcut of the following code.
1.571 - /// \code
1.572 - /// d.init();
1.573 - /// d.addSource(s);
1.574 - /// d.limitedStart(len);
1.575 - /// \endcode
1.576 - void run(Node s, int len) {
1.577 - init();
1.578 - addSource(s);
1.579 - limitedStart(len);
1.580 - }
1.581 -
1.582 - ///@}
1.583 -
1.584 - /// \name Query Functions
1.585 - /// The result of the %BelmannFord algorithm can be obtained using these
1.586 - /// functions.\n
1.587 - /// Before the use of these functions,
1.588 - /// either run() or start() must be called.
1.589 -
1.590 - ///@{
1.591 -
1.592 - /// \brief Copies the shortest path to \c t into \c p
1.593 - ///
1.594 - /// This function copies the shortest path to \c t into \c p.
1.595 - /// If it \c t is a source itself or unreachable, then it does not
1.596 - /// alter \c p.
1.597 - ///
1.598 - /// \return Returns \c true if a path to \c t was actually copied to \c p,
1.599 - /// \c false otherwise.
1.600 - /// \sa DirPath
1.601 - template <typename Path>
1.602 - bool getPath(Path &p, Node t) {
1.603 - if(reached(t)) {
1.604 - p.clear();
1.605 - typename Path::Builder b(p);
1.606 - for(b.setStartNode(t);predEdge(t)!=INVALID;t=predNode(t))
1.607 - b.pushFront(predEdge(t));
1.608 - b.commit();
1.609 - return true;
1.610 - }
1.611 - return false;
1.612 - }
1.613 -
1.614 - /// \brief The distance of a node from the root.
1.615 - ///
1.616 - /// Returns the distance of a node from the root.
1.617 - /// \pre \ref run() must be called before using this function.
1.618 - /// \warning If node \c v in unreachable from the root the return value
1.619 - /// of this funcion is undefined.
1.620 - Value dist(Node v) const { return (*_dist)[v]; }
1.621 -
1.622 - /// \brief Returns the 'previous edge' of the shortest path tree.
1.623 - ///
1.624 - /// For a node \c v it returns the 'previous edge' of the shortest path
1.625 - /// tree, i.e. it returns the last edge of a shortest path from the root
1.626 - /// to \c v. It is \ref INVALID if \c v is unreachable from the root or
1.627 - /// if \c v=s. The shortest path tree used here is equal to the shortest
1.628 - /// path tree used in \ref predNode().
1.629 - /// \pre \ref run() must be called before using
1.630 - /// this function.
1.631 - Edge predEdge(Node v) const { return (*_pred)[v]; }
1.632 -
1.633 - /// \brief Returns the 'previous node' of the shortest path tree.
1.634 - ///
1.635 - /// For a node \c v it returns the 'previous node' of the shortest path
1.636 - /// tree, i.e. it returns the last but one node from a shortest path from
1.637 - /// the root to \c /v. It is INVALID if \c v is unreachable from the root
1.638 - /// or if \c v=s. The shortest path tree used here is equal to the
1.639 - /// shortest path tree used in \ref predEdge(). \pre \ref run() must be
1.640 - /// called before using this function.
1.641 - Node predNode(Node v) const {
1.642 - return (*_pred)[v] == INVALID ? INVALID : graph->source((*_pred)[v]);
1.643 - }
1.644 -
1.645 - /// \brief Returns a reference to the NodeMap of distances.
1.646 - ///
1.647 - /// Returns a reference to the NodeMap of distances. \pre \ref run() must
1.648 - /// be called before using this function.
1.649 - const DistMap &distMap() const { return *_dist;}
1.650 -
1.651 - /// \brief Returns a reference to the shortest path tree map.
1.652 - ///
1.653 - /// Returns a reference to the NodeMap of the edges of the
1.654 - /// shortest path tree.
1.655 - /// \pre \ref run() must be called before using this function.
1.656 - const PredMap &predMap() const { return *_pred; }
1.657 -
1.658 - /// \brief Checks if a node is reachable from the root.
1.659 - ///
1.660 - /// Returns \c true if \c v is reachable from the root.
1.661 - /// \pre \ref run() must be called before using this function.
1.662 - ///
1.663 - bool reached(Node v) { return (*_dist)[v] != OperationTraits::infinity(); }
1.664 -
1.665 - ///@}
1.666 - };
1.667 -
1.668 - /// \brief Default traits class of BelmannFord function.
1.669 - ///
1.670 - /// Default traits class of BelmannFord function.
1.671 - /// \param _Graph Graph type.
1.672 - /// \param _LengthMap Type of length map.
1.673 - template <typename _Graph, typename _LengthMap>
1.674 - struct BelmannFordWizardDefaultTraits {
1.675 - /// \brief The graph type the algorithm runs on.
1.676 - typedef _Graph Graph;
1.677 -
1.678 - /// \brief The type of the map that stores the edge lengths.
1.679 - ///
1.680 - /// The type of the map that stores the edge lengths.
1.681 - /// It must meet the \ref concept::ReadMap "ReadMap" concept.
1.682 - typedef _LengthMap LengthMap;
1.683 -
1.684 - /// \brief The value type of the length map.
1.685 - typedef typename _LengthMap::Value Value;
1.686 -
1.687 - /// \brief Operation traits for belmann-ford algorithm.
1.688 - ///
1.689 - /// It defines the infinity type on the given Value type
1.690 - /// and the used operation.
1.691 - /// \see BelmannFordDefaultOperationTraits
1.692 - typedef BelmannFordDefaultOperationTraits<Value> OperationTraits;
1.693 -
1.694 - /// \brief The type of the map that stores the last
1.695 - /// edges of the shortest paths.
1.696 - ///
1.697 - /// The type of the map that stores the last
1.698 - /// edges of the shortest paths.
1.699 - /// It must meet the \ref concept::WriteMap "WriteMap" concept.
1.700 - typedef NullMap <typename _Graph::Node,typename _Graph::Edge> PredMap;
1.701 -
1.702 - /// \brief Instantiates a PredMap.
1.703 - ///
1.704 - /// This function instantiates a \ref PredMap.
1.705 - static PredMap *createPredMap(const _Graph &) {
1.706 - return new PredMap();
1.707 - }
1.708 - /// \brief The type of the map that stores the dists of the nodes.
1.709 - ///
1.710 - /// The type of the map that stores the dists of the nodes.
1.711 - /// It must meet the \ref concept::WriteMap "WriteMap" concept.
1.712 - typedef NullMap<typename Graph::Node, Value> DistMap;
1.713 - /// \brief Instantiates a DistMap.
1.714 - ///
1.715 - /// This function instantiates a \ref DistMap.
1.716 - static DistMap *createDistMap(const _Graph &) {
1.717 - return new DistMap();
1.718 - }
1.719 - };
1.720 -
1.721 - /// \brief Default traits used by \ref BelmannFordWizard
1.722 - ///
1.723 - /// To make it easier to use BelmannFord algorithm
1.724 - /// we have created a wizard class.
1.725 - /// This \ref BelmannFordWizard class needs default traits,
1.726 - /// as well as the \ref BelmannFord class.
1.727 - /// The \ref BelmannFordWizardBase is a class to be the default traits of the
1.728 - /// \ref BelmannFordWizard class.
1.729 - /// \todo More named parameters are required...
1.730 - template<class _Graph,class _LengthMap>
1.731 - class BelmannFordWizardBase
1.732 - : public BelmannFordWizardDefaultTraits<_Graph,_LengthMap> {
1.733 -
1.734 - typedef BelmannFordWizardDefaultTraits<_Graph,_LengthMap> Base;
1.735 - protected:
1.736 - /// Type of the nodes in the graph.
1.737 - typedef typename Base::Graph::Node Node;
1.738 -
1.739 - /// Pointer to the underlying graph.
1.740 - void *_graph;
1.741 - /// Pointer to the length map
1.742 - void *_length;
1.743 - ///Pointer to the map of predecessors edges.
1.744 - void *_pred;
1.745 - ///Pointer to the map of distances.
1.746 - void *_dist;
1.747 - ///Pointer to the source node.
1.748 - Node _source;
1.749 -
1.750 - public:
1.751 - /// Constructor.
1.752 -
1.753 - /// This constructor does not require parameters, therefore it initiates
1.754 - /// all of the attributes to default values (0, INVALID).
1.755 - BelmannFordWizardBase() : _graph(0), _length(0), _pred(0),
1.756 - _dist(0), _source(INVALID) {}
1.757 -
1.758 - /// Constructor.
1.759 -
1.760 - /// This constructor requires some parameters,
1.761 - /// listed in the parameters list.
1.762 - /// Others are initiated to 0.
1.763 - /// \param graph is the initial value of \ref _graph
1.764 - /// \param length is the initial value of \ref _length
1.765 - /// \param source is the initial value of \ref _source
1.766 - BelmannFordWizardBase(const _Graph& graph,
1.767 - const _LengthMap& length,
1.768 - Node source = INVALID) :
1.769 - _graph((void *)&graph), _length((void *)&length), _pred(0),
1.770 - _dist(0), _source(source) {}
1.771 -
1.772 - };
1.773 -
1.774 - /// A class to make the usage of BelmannFord algorithm easier
1.775 -
1.776 - /// This class is created to make it easier to use BelmannFord algorithm.
1.777 - /// It uses the functions and features of the plain \ref BelmannFord,
1.778 - /// but it is much simpler to use it.
1.779 - ///
1.780 - /// Simplicity means that the way to change the types defined
1.781 - /// in the traits class is based on functions that returns the new class
1.782 - /// and not on templatable built-in classes.
1.783 - /// When using the plain \ref BelmannFord
1.784 - /// the new class with the modified type comes from
1.785 - /// the original class by using the ::
1.786 - /// operator. In the case of \ref BelmannFordWizard only
1.787 - /// a function have to be called and it will
1.788 - /// return the needed class.
1.789 - ///
1.790 - /// It does not have own \ref run method. When its \ref run method is called
1.791 - /// it initiates a plain \ref BelmannFord class, and calls the \ref
1.792 - /// BelmannFord::run method of it.
1.793 - template<class _Traits>
1.794 - class BelmannFordWizard : public _Traits {
1.795 - typedef _Traits Base;
1.796 -
1.797 - ///The type of the underlying graph.
1.798 - typedef typename _Traits::Graph Graph;
1.799 -
1.800 - typedef typename Graph::Node Node;
1.801 - typedef typename Graph::NodeIt NodeIt;
1.802 - typedef typename Graph::Edge Edge;
1.803 - typedef typename Graph::OutEdgeIt EdgeIt;
1.804 -
1.805 - ///The type of the map that stores the edge lengths.
1.806 - typedef typename _Traits::LengthMap LengthMap;
1.807 -
1.808 - ///The type of the length of the edges.
1.809 - typedef typename LengthMap::Value Value;
1.810 -
1.811 - ///\brief The type of the map that stores the last
1.812 - ///edges of the shortest paths.
1.813 - typedef typename _Traits::PredMap PredMap;
1.814 -
1.815 - ///The type of the map that stores the dists of the nodes.
1.816 - typedef typename _Traits::DistMap DistMap;
1.817 -
1.818 - public:
1.819 - /// Constructor.
1.820 - BelmannFordWizard() : _Traits() {}
1.821 -
1.822 - /// \brief Constructor that requires parameters.
1.823 - ///
1.824 - /// Constructor that requires parameters.
1.825 - /// These parameters will be the default values for the traits class.
1.826 - BelmannFordWizard(const Graph& graph, const LengthMap& length,
1.827 - Node source = INVALID)
1.828 - : _Traits(graph, length, source) {}
1.829 -
1.830 - /// \brief Copy constructor
1.831 - BelmannFordWizard(const _Traits &b) : _Traits(b) {}
1.832 -
1.833 - ~BelmannFordWizard() {}
1.834 -
1.835 - /// \brief Runs BelmannFord algorithm from a given node.
1.836 - ///
1.837 - /// Runs BelmannFord algorithm from a given node.
1.838 - /// The node can be given by the \ref source function.
1.839 - void run() {
1.840 - if(Base::_source == INVALID) throw UninitializedParameter();
1.841 - BelmannFord<Graph,LengthMap,_Traits>
1.842 - bf(*(Graph*)Base::_graph, *(LengthMap*)Base::_length);
1.843 - if (Base::_pred) bf.predMap(*(PredMap*)Base::_pred);
1.844 - if (Base::_dist) bf.distMap(*(DistMap*)Base::_dist);
1.845 - bf.run(Base::_source);
1.846 - }
1.847 -
1.848 - /// \brief Runs BelmannFord algorithm from the given node.
1.849 - ///
1.850 - /// Runs BelmannFord algorithm from the given node.
1.851 - /// \param source is the given source.
1.852 - void run(Node source) {
1.853 - Base::_source = source;
1.854 - run();
1.855 - }
1.856 -
1.857 - template<class T>
1.858 - struct DefPredMapBase : public Base {
1.859 - typedef T PredMap;
1.860 - static PredMap *createPredMap(const Graph &) { return 0; };
1.861 - DefPredMapBase(const _Traits &b) : _Traits(b) {}
1.862 - };
1.863 -
1.864 - ///\brief \ref named-templ-param "Named parameter"
1.865 - ///function for setting PredMap type
1.866 - ///
1.867 - /// \ref named-templ-param "Named parameter"
1.868 - ///function for setting PredMap type
1.869 - ///
1.870 - template<class T>
1.871 - BelmannFordWizard<DefPredMapBase<T> > predMap(const T &t)
1.872 - {
1.873 - Base::_pred=(void *)&t;
1.874 - return BelmannFordWizard<DefPredMapBase<T> >(*this);
1.875 - }
1.876 -
1.877 - template<class T>
1.878 - struct DefDistMapBase : public Base {
1.879 - typedef T DistMap;
1.880 - static DistMap *createDistMap(const Graph &) { return 0; };
1.881 - DefDistMapBase(const _Traits &b) : _Traits(b) {}
1.882 - };
1.883 -
1.884 - ///\brief \ref named-templ-param "Named parameter"
1.885 - ///function for setting DistMap type
1.886 - ///
1.887 - /// \ref named-templ-param "Named parameter"
1.888 - ///function for setting DistMap type
1.889 - ///
1.890 - template<class T>
1.891 - BelmannFordWizard<DefDistMapBase<T> > distMap(const T &t) {
1.892 - Base::_dist=(void *)&t;
1.893 - return BelmannFordWizard<DefDistMapBase<T> >(*this);
1.894 - }
1.895 -
1.896 - template<class T>
1.897 - struct DefOperationTraitsBase : public Base {
1.898 - typedef T OperationTraits;
1.899 - DefOperationTraitsBase(const _Traits &b) : _Traits(b) {}
1.900 - };
1.901 -
1.902 - ///\brief \ref named-templ-param "Named parameter"
1.903 - ///function for setting OperationTraits type
1.904 - ///
1.905 - /// \ref named-templ-param "Named parameter"
1.906 - ///function for setting OperationTraits type
1.907 - ///
1.908 - template<class T>
1.909 - BelmannFordWizard<DefOperationTraitsBase<T> > distMap() {
1.910 - return BelmannFordWizard<DefDistMapBase<T> >(*this);
1.911 - }
1.912 -
1.913 - /// \brief Sets the source node, from which the BelmannFord algorithm runs.
1.914 - ///
1.915 - /// Sets the source node, from which the BelmannFord algorithm runs.
1.916 - /// \param source is the source node.
1.917 - BelmannFordWizard<_Traits>& source(Node source) {
1.918 - Base::_source = source;
1.919 - return *this;
1.920 - }
1.921 -
1.922 - };
1.923 -
1.924 - /// \brief Function type interface for BelmannFord algorithm.
1.925 - ///
1.926 - /// \ingroup flowalgs
1.927 - /// Function type interface for BelmannFord algorithm.
1.928 - ///
1.929 - /// This function also has several \ref named-templ-func-param
1.930 - /// "named parameters", they are declared as the members of class
1.931 - /// \ref BelmannFordWizard.
1.932 - /// The following
1.933 - /// example shows how to use these parameters.
1.934 - /// \code
1.935 - /// belmannford(g,length,source).predMap(preds).run();
1.936 - /// \endcode
1.937 - /// \warning Don't forget to put the \ref BelmannFordWizard::run() "run()"
1.938 - /// to the end of the parameter list.
1.939 - /// \sa BelmannFordWizard
1.940 - /// \sa BelmannFord
1.941 - template<class _Graph, class _LengthMap>
1.942 - BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> >
1.943 - belmannFord(const _Graph& graph,
1.944 - const _LengthMap& length,
1.945 - typename _Graph::Node source = INVALID) {
1.946 - return BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> >
1.947 - (graph, length, source);
1.948 - }
1.949 -
1.950 -} //END OF NAMESPACE LEMON
1.951 -
1.952 -#endif
1.953 -