[1699] | 1 | /* -*- C++ -*- |
---|
| 2 | * lemon/belmann_ford.h - Part of LEMON, a generic C++ optimization library |
---|
| 3 | * |
---|
| 4 | * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport |
---|
| 5 | * (Egervary Research Group on Combinatorial Optimization, EGRES). |
---|
| 6 | * |
---|
| 7 | * Permission to use, modify and distribute this software is granted |
---|
| 8 | * provided that this copyright notice appears in all copies. For |
---|
| 9 | * precise terms see the accompanying LICENSE file. |
---|
| 10 | * |
---|
| 11 | * This software is provided "AS IS" with no warranty of any kind, |
---|
| 12 | * express or implied, and with no claim as to its suitability for any |
---|
| 13 | * purpose. |
---|
| 14 | * |
---|
| 15 | */ |
---|
| 16 | |
---|
| 17 | #ifndef LEMON_BELMANN_FORD_H |
---|
| 18 | #define LEMON_BELMANN_FORD_H |
---|
| 19 | |
---|
| 20 | ///\ingroup flowalgs |
---|
| 21 | /// \file |
---|
| 22 | /// \brief BelmannFord algorithm. |
---|
| 23 | /// |
---|
| 24 | /// \todo getPath() should be implemented! (also for BFS and DFS) |
---|
| 25 | |
---|
| 26 | #include <lemon/list_graph.h> |
---|
| 27 | #include <lemon/invalid.h> |
---|
| 28 | #include <lemon/error.h> |
---|
| 29 | #include <lemon/maps.h> |
---|
| 30 | |
---|
| 31 | #include <limits> |
---|
| 32 | |
---|
| 33 | namespace lemon { |
---|
| 34 | |
---|
| 35 | /// \brief Default OperationTraits for the BelmannFord algorithm class. |
---|
| 36 | /// |
---|
| 37 | /// It defines all computational operations and constants which are |
---|
| 38 | /// used in the belmann ford algorithm. The default implementation |
---|
| 39 | /// is based on the numeric_limits class. If the numeric type does not |
---|
| 40 | /// have infinity value then the maximum value is used as extremal |
---|
| 41 | /// infinity value. |
---|
| 42 | template < |
---|
| 43 | typename Value, |
---|
| 44 | bool has_infinity = std::numeric_limits<Value>::has_infinity> |
---|
| 45 | struct BelmannFordDefaultOperationTraits { |
---|
| 46 | /// \brief Gives back the zero value of the type. |
---|
| 47 | static Value zero() { |
---|
| 48 | return static_cast<Value>(0); |
---|
| 49 | } |
---|
| 50 | /// \brief Gives back the positive infinity value of the type. |
---|
| 51 | static Value infinity() { |
---|
| 52 | return std::numeric_limits<Value>::infinity(); |
---|
| 53 | } |
---|
| 54 | /// \brief Gives back the sum of the given two elements. |
---|
| 55 | static Value plus(const Value& left, const Value& right) { |
---|
| 56 | return left + right; |
---|
| 57 | } |
---|
| 58 | /// \brief Gives back true only if the first value less than the second. |
---|
| 59 | static bool less(const Value& left, const Value& right) { |
---|
| 60 | return left < right; |
---|
| 61 | } |
---|
| 62 | }; |
---|
| 63 | |
---|
| 64 | template <typename Value> |
---|
| 65 | struct BelmannFordDefaultOperationTraits<Value, false> { |
---|
| 66 | static Value zero() { |
---|
| 67 | return static_cast<Value>(0); |
---|
| 68 | } |
---|
| 69 | static Value infinity() { |
---|
| 70 | return std::numeric_limits<Value>::max(); |
---|
| 71 | } |
---|
| 72 | static Value plus(const Value& left, const Value& right) { |
---|
| 73 | if (left == infinity() || right == infinity()) return infinity(); |
---|
| 74 | return left + right; |
---|
| 75 | } |
---|
| 76 | static bool less(const Value& left, const Value& right) { |
---|
| 77 | return left < right; |
---|
| 78 | } |
---|
| 79 | }; |
---|
| 80 | |
---|
| 81 | /// \brief Default traits class of BelmannFord class. |
---|
| 82 | /// |
---|
| 83 | /// Default traits class of BelmannFord class. |
---|
| 84 | /// \param _Graph Graph type. |
---|
| 85 | /// \param _LegthMap Type of length map. |
---|
| 86 | template<class _Graph, class _LengthMap> |
---|
| 87 | struct BelmannFordDefaultTraits { |
---|
| 88 | /// The graph type the algorithm runs on. |
---|
| 89 | typedef _Graph Graph; |
---|
| 90 | |
---|
| 91 | /// \brief The type of the map that stores the edge lengths. |
---|
| 92 | /// |
---|
| 93 | /// The type of the map that stores the edge lengths. |
---|
| 94 | /// It must meet the \ref concept::ReadMap "ReadMap" concept. |
---|
| 95 | typedef _LengthMap LengthMap; |
---|
| 96 | |
---|
| 97 | // The type of the length of the edges. |
---|
| 98 | typedef typename _LengthMap::Value Value; |
---|
| 99 | |
---|
| 100 | /// \brief Operation traits for belmann-ford algorithm. |
---|
| 101 | /// |
---|
| 102 | /// It defines the infinity type on the given Value type |
---|
| 103 | /// and the used operation. |
---|
| 104 | /// \see BelmannFordDefaultOperationTraits |
---|
| 105 | typedef BelmannFordDefaultOperationTraits<Value> OperationTraits; |
---|
| 106 | |
---|
| 107 | /// \brief The type of the map that stores the last edges of the |
---|
| 108 | /// shortest paths. |
---|
| 109 | /// |
---|
| 110 | /// The type of the map that stores the last |
---|
| 111 | /// edges of the shortest paths. |
---|
| 112 | /// It must meet the \ref concept::WriteMap "WriteMap" concept. |
---|
| 113 | /// |
---|
| 114 | typedef typename Graph::template NodeMap<typename _Graph::Edge> PredMap; |
---|
| 115 | |
---|
| 116 | /// \brief Instantiates a PredMap. |
---|
| 117 | /// |
---|
| 118 | /// This function instantiates a \ref PredMap. |
---|
| 119 | /// \param G is the graph, to which we would like to define the PredMap. |
---|
| 120 | /// \todo The graph alone may be insufficient for the initialization |
---|
| 121 | static PredMap *createPredMap(const _Graph& graph) { |
---|
| 122 | return new PredMap(graph); |
---|
| 123 | } |
---|
| 124 | |
---|
| 125 | /// \brief The type of the map that stores the dists of the nodes. |
---|
| 126 | /// |
---|
| 127 | /// The type of the map that stores the dists of the nodes. |
---|
| 128 | /// It must meet the \ref concept::WriteMap "WriteMap" concept. |
---|
| 129 | /// |
---|
| 130 | typedef typename Graph::template NodeMap<typename _LengthMap::Value> |
---|
| 131 | DistMap; |
---|
| 132 | |
---|
| 133 | /// \brief Instantiates a DistMap. |
---|
| 134 | /// |
---|
| 135 | /// This function instantiates a \ref DistMap. |
---|
| 136 | /// \param G is the graph, to which we would like to define the |
---|
| 137 | /// \ref DistMap |
---|
| 138 | static DistMap *createDistMap(const _Graph& graph) { |
---|
| 139 | return new DistMap(graph); |
---|
| 140 | } |
---|
| 141 | |
---|
| 142 | }; |
---|
| 143 | |
---|
| 144 | /// \brief BelmannFord algorithm class. |
---|
| 145 | /// |
---|
| 146 | /// \ingroup flowalgs |
---|
[1723] | 147 | /// This class provides an efficient implementation of \c Belmann-Ford |
---|
[1699] | 148 | /// algorithm. The edge lengths are passed to the algorithm using a |
---|
| 149 | /// \ref concept::ReadMap "ReadMap", so it is easy to change it to any |
---|
| 150 | /// kind of length. |
---|
| 151 | /// |
---|
[1723] | 152 | /// The Belmann-Ford algorithm solves the shortest path from one node |
---|
| 153 | /// problem when the edges can have negative length but the graph should |
---|
| 154 | /// not contain circle with negative sum of length. If we can assume |
---|
| 155 | /// that all edge is non-negative in the graph then the dijkstra algorithm |
---|
| 156 | /// should be used rather. |
---|
| 157 | /// |
---|
| 158 | /// The complexity of the algorithm is O(n * e). |
---|
| 159 | /// |
---|
[1699] | 160 | /// The type of the length is determined by the |
---|
| 161 | /// \ref concept::ReadMap::Value "Value" of the length map. |
---|
| 162 | /// |
---|
| 163 | /// \param _Graph The graph type the algorithm runs on. The default value |
---|
| 164 | /// is \ref ListGraph. The value of _Graph is not used directly by |
---|
| 165 | /// BelmannFord, it is only passed to \ref BelmannFordDefaultTraits. |
---|
| 166 | /// \param _LengthMap This read-only EdgeMap determines the lengths of the |
---|
| 167 | /// edges. The default map type is \ref concept::StaticGraph::EdgeMap |
---|
| 168 | /// "Graph::EdgeMap<int>". The value of _LengthMap is not used directly |
---|
| 169 | /// by BelmannFord, it is only passed to \ref BelmannFordDefaultTraits. |
---|
| 170 | /// \param _Traits Traits class to set various data types used by the |
---|
| 171 | /// algorithm. The default traits class is \ref BelmannFordDefaultTraits |
---|
| 172 | /// "BelmannFordDefaultTraits<_Graph,_LengthMap>". See \ref |
---|
| 173 | /// BelmannFordDefaultTraits for the documentation of a BelmannFord traits |
---|
| 174 | /// class. |
---|
| 175 | /// |
---|
| 176 | /// \author Balazs Dezso |
---|
| 177 | |
---|
[1710] | 178 | #ifdef DOXYGEN |
---|
| 179 | template <typename _Graph, typename _LengthMap, typename _Traits> |
---|
| 180 | #else |
---|
[1699] | 181 | template <typename _Graph=ListGraph, |
---|
| 182 | typename _LengthMap=typename _Graph::template EdgeMap<int>, |
---|
| 183 | typename _Traits=BelmannFordDefaultTraits<_Graph,_LengthMap> > |
---|
[1710] | 184 | #endif |
---|
[1699] | 185 | class BelmannFord { |
---|
| 186 | public: |
---|
| 187 | |
---|
| 188 | /// \brief \ref Exception for uninitialized parameters. |
---|
| 189 | /// |
---|
| 190 | /// This error represents problems in the initialization |
---|
| 191 | /// of the parameters of the algorithms. |
---|
| 192 | |
---|
| 193 | class UninitializedParameter : public lemon::UninitializedParameter { |
---|
| 194 | public: |
---|
| 195 | virtual const char* exceptionName() const { |
---|
| 196 | return "lemon::BelmannFord::UninitializedParameter"; |
---|
| 197 | } |
---|
| 198 | }; |
---|
| 199 | |
---|
| 200 | typedef _Traits Traits; |
---|
| 201 | ///The type of the underlying graph. |
---|
| 202 | typedef typename _Traits::Graph Graph; |
---|
| 203 | |
---|
| 204 | typedef typename Graph::Node Node; |
---|
| 205 | typedef typename Graph::NodeIt NodeIt; |
---|
| 206 | typedef typename Graph::Edge Edge; |
---|
| 207 | typedef typename Graph::EdgeIt EdgeIt; |
---|
| 208 | |
---|
| 209 | /// \brief The type of the length of the edges. |
---|
| 210 | typedef typename _Traits::LengthMap::Value Value; |
---|
| 211 | /// \brief The type of the map that stores the edge lengths. |
---|
| 212 | typedef typename _Traits::LengthMap LengthMap; |
---|
| 213 | /// \brief The type of the map that stores the last |
---|
| 214 | /// edges of the shortest paths. |
---|
| 215 | typedef typename _Traits::PredMap PredMap; |
---|
| 216 | /// \brief The type of the map that stores the dists of the nodes. |
---|
| 217 | typedef typename _Traits::DistMap DistMap; |
---|
| 218 | /// \brief The operation traits. |
---|
| 219 | typedef typename _Traits::OperationTraits OperationTraits; |
---|
| 220 | private: |
---|
| 221 | /// Pointer to the underlying graph. |
---|
| 222 | const Graph *graph; |
---|
| 223 | /// Pointer to the length map |
---|
| 224 | const LengthMap *length; |
---|
| 225 | ///Pointer to the map of predecessors edges. |
---|
| 226 | PredMap *_pred; |
---|
| 227 | ///Indicates if \ref _pred is locally allocated (\c true) or not. |
---|
| 228 | bool local_pred; |
---|
| 229 | ///Pointer to the map of distances. |
---|
| 230 | DistMap *_dist; |
---|
| 231 | ///Indicates if \ref _dist is locally allocated (\c true) or not. |
---|
| 232 | bool local_dist; |
---|
| 233 | |
---|
| 234 | /// Creates the maps if necessary. |
---|
| 235 | void create_maps() { |
---|
| 236 | if(!_pred) { |
---|
| 237 | local_pred = true; |
---|
| 238 | _pred = Traits::createPredMap(*graph); |
---|
| 239 | } |
---|
| 240 | if(!_dist) { |
---|
| 241 | local_dist = true; |
---|
| 242 | _dist = Traits::createDistMap(*graph); |
---|
| 243 | } |
---|
| 244 | } |
---|
| 245 | |
---|
| 246 | public : |
---|
| 247 | |
---|
[1710] | 248 | typedef BelmannFord Create; |
---|
| 249 | |
---|
[1699] | 250 | /// \name Named template parameters |
---|
| 251 | |
---|
| 252 | ///@{ |
---|
| 253 | |
---|
| 254 | template <class T> |
---|
| 255 | struct DefPredMapTraits : public Traits { |
---|
| 256 | typedef T PredMap; |
---|
[1710] | 257 | static PredMap *createPredMap(const Graph&) { |
---|
[1699] | 258 | throw UninitializedParameter(); |
---|
| 259 | } |
---|
| 260 | }; |
---|
| 261 | |
---|
| 262 | /// \brief \ref named-templ-param "Named parameter" for setting PredMap |
---|
| 263 | /// type |
---|
| 264 | /// \ref named-templ-param "Named parameter" for setting PredMap type |
---|
| 265 | /// |
---|
| 266 | template <class T> |
---|
[1710] | 267 | struct DefPredMap { |
---|
| 268 | typedef BelmannFord< Graph, LengthMap, DefPredMapTraits<T> > Create; |
---|
| 269 | }; |
---|
[1699] | 270 | |
---|
| 271 | template <class T> |
---|
| 272 | struct DefDistMapTraits : public Traits { |
---|
| 273 | typedef T DistMap; |
---|
| 274 | static DistMap *createDistMap(const Graph& graph) { |
---|
| 275 | throw UninitializedParameter(); |
---|
| 276 | } |
---|
| 277 | }; |
---|
| 278 | |
---|
| 279 | /// \brief \ref named-templ-param "Named parameter" for setting DistMap |
---|
| 280 | /// type |
---|
| 281 | /// |
---|
| 282 | /// \ref named-templ-param "Named parameter" for setting DistMap type |
---|
| 283 | /// |
---|
| 284 | template <class T> |
---|
[1710] | 285 | struct DefDistMap |
---|
| 286 | : public BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > { |
---|
| 287 | typedef BelmannFord< Graph, LengthMap, DefDistMapTraits<T> > Create; |
---|
| 288 | }; |
---|
[1699] | 289 | |
---|
| 290 | template <class T> |
---|
| 291 | struct DefOperationTraitsTraits : public Traits { |
---|
| 292 | typedef T OperationTraits; |
---|
| 293 | }; |
---|
| 294 | |
---|
| 295 | /// \brief \ref named-templ-param "Named parameter" for setting |
---|
| 296 | /// OperationTraits type |
---|
| 297 | /// |
---|
[1710] | 298 | /// \ref named-templ-param "Named parameter" for setting OperationTraits |
---|
| 299 | /// type |
---|
[1699] | 300 | template <class T> |
---|
[1710] | 301 | struct DefOperationTraits |
---|
[1699] | 302 | : public BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> > { |
---|
| 303 | typedef BelmannFord< Graph, LengthMap, DefOperationTraitsTraits<T> > |
---|
[1710] | 304 | Create; |
---|
[1699] | 305 | }; |
---|
| 306 | |
---|
| 307 | ///@} |
---|
| 308 | |
---|
[1710] | 309 | protected: |
---|
| 310 | |
---|
| 311 | BelmannFord() {} |
---|
| 312 | |
---|
[1699] | 313 | public: |
---|
| 314 | |
---|
| 315 | /// \brief Constructor. |
---|
| 316 | /// |
---|
| 317 | /// \param _graph the graph the algorithm will run on. |
---|
| 318 | /// \param _length the length map used by the algorithm. |
---|
| 319 | BelmannFord(const Graph& _graph, const LengthMap& _length) : |
---|
| 320 | graph(&_graph), length(&_length), |
---|
| 321 | _pred(0), local_pred(false), |
---|
| 322 | _dist(0), local_dist(false) {} |
---|
| 323 | |
---|
| 324 | ///Destructor. |
---|
| 325 | ~BelmannFord() { |
---|
| 326 | if(local_pred) delete _pred; |
---|
| 327 | if(local_dist) delete _dist; |
---|
| 328 | } |
---|
| 329 | |
---|
| 330 | /// \brief Sets the length map. |
---|
| 331 | /// |
---|
| 332 | /// Sets the length map. |
---|
| 333 | /// \return \c (*this) |
---|
| 334 | BelmannFord &lengthMap(const LengthMap &m) { |
---|
| 335 | length = &m; |
---|
| 336 | return *this; |
---|
| 337 | } |
---|
| 338 | |
---|
| 339 | /// \brief Sets the map storing the predecessor edges. |
---|
| 340 | /// |
---|
| 341 | /// Sets the map storing the predecessor edges. |
---|
| 342 | /// If you don't use this function before calling \ref run(), |
---|
| 343 | /// it will allocate one. The destuctor deallocates this |
---|
| 344 | /// automatically allocated map, of course. |
---|
| 345 | /// \return \c (*this) |
---|
| 346 | BelmannFord &predMap(PredMap &m) { |
---|
| 347 | if(local_pred) { |
---|
| 348 | delete _pred; |
---|
| 349 | local_pred=false; |
---|
| 350 | } |
---|
| 351 | _pred = &m; |
---|
| 352 | return *this; |
---|
| 353 | } |
---|
| 354 | |
---|
| 355 | /// \brief Sets the map storing the distances calculated by the algorithm. |
---|
| 356 | /// |
---|
| 357 | /// Sets the map storing the distances calculated by the algorithm. |
---|
| 358 | /// If you don't use this function before calling \ref run(), |
---|
| 359 | /// it will allocate one. The destuctor deallocates this |
---|
| 360 | /// automatically allocated map, of course. |
---|
| 361 | /// \return \c (*this) |
---|
| 362 | BelmannFord &distMap(DistMap &m) { |
---|
| 363 | if(local_dist) { |
---|
| 364 | delete _dist; |
---|
| 365 | local_dist=false; |
---|
| 366 | } |
---|
| 367 | _dist = &m; |
---|
| 368 | return *this; |
---|
| 369 | } |
---|
| 370 | |
---|
| 371 | /// \name Execution control |
---|
| 372 | /// The simplest way to execute the algorithm is to use |
---|
| 373 | /// one of the member functions called \c run(...). |
---|
| 374 | /// \n |
---|
| 375 | /// If you need more control on the execution, |
---|
| 376 | /// first you must call \ref init(), then you can add several source nodes |
---|
| 377 | /// with \ref addSource(). |
---|
| 378 | /// Finally \ref start() will perform the actual path |
---|
| 379 | /// computation. |
---|
| 380 | |
---|
| 381 | ///@{ |
---|
| 382 | |
---|
| 383 | /// \brief Initializes the internal data structures. |
---|
| 384 | /// |
---|
| 385 | /// Initializes the internal data structures. |
---|
[1710] | 386 | void init(const Value value = OperationTraits::infinity()) { |
---|
[1699] | 387 | create_maps(); |
---|
| 388 | for (NodeIt it(*graph); it != INVALID; ++it) { |
---|
| 389 | _pred->set(it, INVALID); |
---|
[1710] | 390 | _dist->set(it, value); |
---|
[1699] | 391 | } |
---|
| 392 | } |
---|
| 393 | |
---|
| 394 | /// \brief Adds a new source node. |
---|
| 395 | /// |
---|
| 396 | /// The optional second parameter is the initial distance of the node. |
---|
| 397 | /// It just sets the distance of the node to the given value. |
---|
| 398 | void addSource(Node source, Value dst = OperationTraits::zero()) { |
---|
| 399 | _dist->set(source, dst); |
---|
| 400 | } |
---|
| 401 | |
---|
| 402 | /// \brief Executes the algorithm. |
---|
| 403 | /// |
---|
| 404 | /// \pre init() must be called and at least one node should be added |
---|
| 405 | /// with addSource() before using this function. |
---|
| 406 | /// |
---|
| 407 | /// This method runs the %BelmannFord algorithm from the root node(s) |
---|
| 408 | /// in order to compute the shortest path to each node. The algorithm |
---|
| 409 | /// computes |
---|
| 410 | /// - The shortest path tree. |
---|
| 411 | /// - The distance of each node from the root(s). |
---|
| 412 | void start() { |
---|
[1723] | 413 | int num = countNodes(*graph) - 1; |
---|
| 414 | for (int i = 0; i < num; ++i) { |
---|
[1741] | 415 | bool done = true; |
---|
[1699] | 416 | for (EdgeIt it(*graph); it != INVALID; ++it) { |
---|
| 417 | Node source = graph->source(it); |
---|
| 418 | Node target = graph->target(it); |
---|
| 419 | Value relaxed = |
---|
| 420 | OperationTraits::plus((*_dist)[source], (*length)[it]); |
---|
| 421 | if (OperationTraits::less(relaxed, (*_dist)[target])) { |
---|
| 422 | _pred->set(target, it); |
---|
| 423 | _dist->set(target, relaxed); |
---|
[1741] | 424 | done = false; |
---|
[1699] | 425 | } |
---|
| 426 | } |
---|
[1741] | 427 | if (done) return; |
---|
[1699] | 428 | } |
---|
| 429 | } |
---|
[1723] | 430 | |
---|
[1741] | 431 | /// \brief Executes the algorithm and checks the negative circles. |
---|
[1723] | 432 | /// |
---|
| 433 | /// \pre init() must be called and at least one node should be added |
---|
| 434 | /// with addSource() before using this function. If there is |
---|
| 435 | /// a negative circle in the graph it gives back false. |
---|
| 436 | /// |
---|
| 437 | /// This method runs the %BelmannFord algorithm from the root node(s) |
---|
| 438 | /// in order to compute the shortest path to each node. The algorithm |
---|
| 439 | /// computes |
---|
| 440 | /// - The shortest path tree. |
---|
| 441 | /// - The distance of each node from the root(s). |
---|
| 442 | bool checkedStart() { |
---|
| 443 | int num = countNodes(*graph); |
---|
| 444 | for (int i = 0; i < num; ++i) { |
---|
[1741] | 445 | bool done = true; |
---|
[1723] | 446 | for (EdgeIt it(*graph); it != INVALID; ++it) { |
---|
| 447 | Node source = graph->source(it); |
---|
| 448 | Node target = graph->target(it); |
---|
| 449 | Value relaxed = |
---|
| 450 | OperationTraits::plus((*_dist)[source], (*length)[it]); |
---|
| 451 | if (OperationTraits::less(relaxed, (*_dist)[target])) { |
---|
| 452 | _pred->set(target, it); |
---|
| 453 | _dist->set(target, relaxed); |
---|
[1741] | 454 | done = false; |
---|
[1723] | 455 | } |
---|
| 456 | } |
---|
[1741] | 457 | if (done) return true; |
---|
[1723] | 458 | } |
---|
| 459 | return false; |
---|
| 460 | } |
---|
[1699] | 461 | |
---|
| 462 | /// \brief Runs %BelmannFord algorithm from node \c s. |
---|
| 463 | /// |
---|
| 464 | /// This method runs the %BelmannFord algorithm from a root node \c s |
---|
| 465 | /// in order to compute the shortest path to each node. The algorithm |
---|
| 466 | /// computes |
---|
| 467 | /// - The shortest path tree. |
---|
| 468 | /// - The distance of each node from the root. |
---|
| 469 | /// |
---|
| 470 | /// \note d.run(s) is just a shortcut of the following code. |
---|
| 471 | /// \code |
---|
| 472 | /// d.init(); |
---|
| 473 | /// d.addSource(s); |
---|
| 474 | /// d.start(); |
---|
| 475 | /// \endcode |
---|
| 476 | void run(Node s) { |
---|
| 477 | init(); |
---|
| 478 | addSource(s); |
---|
| 479 | start(); |
---|
| 480 | } |
---|
| 481 | |
---|
| 482 | ///@} |
---|
| 483 | |
---|
| 484 | /// \name Query Functions |
---|
| 485 | /// The result of the %BelmannFord algorithm can be obtained using these |
---|
| 486 | /// functions.\n |
---|
| 487 | /// Before the use of these functions, |
---|
| 488 | /// either run() or start() must be called. |
---|
| 489 | |
---|
| 490 | ///@{ |
---|
| 491 | |
---|
| 492 | /// \brief Copies the shortest path to \c t into \c p |
---|
| 493 | /// |
---|
| 494 | /// This function copies the shortest path to \c t into \c p. |
---|
| 495 | /// If it \c t is a source itself or unreachable, then it does not |
---|
| 496 | /// alter \c p. |
---|
| 497 | /// \todo Is it the right way to handle unreachable nodes? |
---|
| 498 | /// \return Returns \c true if a path to \c t was actually copied to \c p, |
---|
| 499 | /// \c false otherwise. |
---|
| 500 | /// \sa DirPath |
---|
| 501 | template <typename Path> |
---|
| 502 | bool getPath(Path &p, Node t) { |
---|
| 503 | if(reached(t)) { |
---|
| 504 | p.clear(); |
---|
| 505 | typename Path::Builder b(p); |
---|
| 506 | for(b.setStartNode(t);pred(t)!=INVALID;t=predNode(t)) |
---|
| 507 | b.pushFront(pred(t)); |
---|
| 508 | b.commit(); |
---|
| 509 | return true; |
---|
| 510 | } |
---|
| 511 | return false; |
---|
| 512 | } |
---|
| 513 | |
---|
| 514 | /// \brief The distance of a node from the root. |
---|
| 515 | /// |
---|
| 516 | /// Returns the distance of a node from the root. |
---|
| 517 | /// \pre \ref run() must be called before using this function. |
---|
| 518 | /// \warning If node \c v in unreachable from the root the return value |
---|
| 519 | /// of this funcion is undefined. |
---|
| 520 | Value dist(Node v) const { return (*_dist)[v]; } |
---|
| 521 | |
---|
| 522 | /// \brief Returns the 'previous edge' of the shortest path tree. |
---|
| 523 | /// |
---|
| 524 | /// For a node \c v it returns the 'previous edge' of the shortest path |
---|
| 525 | /// tree, i.e. it returns the last edge of a shortest path from the root |
---|
| 526 | /// to \c v. It is \ref INVALID if \c v is unreachable from the root or |
---|
| 527 | /// if \c v=s. The shortest path tree used here is equal to the shortest |
---|
| 528 | /// path tree used in \ref predNode(). |
---|
| 529 | /// \pre \ref run() must be called before using |
---|
| 530 | /// this function. |
---|
| 531 | /// \todo predEdge could be a better name. |
---|
| 532 | Edge pred(Node v) const { return (*_pred)[v]; } |
---|
| 533 | |
---|
| 534 | /// \brief Returns the 'previous node' of the shortest path tree. |
---|
| 535 | /// |
---|
| 536 | /// For a node \c v it returns the 'previous node' of the shortest path |
---|
| 537 | /// tree, i.e. it returns the last but one node from a shortest path from |
---|
| 538 | /// the root to \c /v. It is INVALID if \c v is unreachable from the root |
---|
| 539 | /// or if \c v=s. The shortest path tree used here is equal to the |
---|
| 540 | /// shortest path tree used in \ref pred(). \pre \ref run() must be |
---|
| 541 | /// called before using this function. |
---|
| 542 | Node predNode(Node v) const { |
---|
| 543 | return (*_pred)[v] == INVALID ? INVALID : graph->source((*_pred)[v]); |
---|
| 544 | } |
---|
| 545 | |
---|
| 546 | /// \brief Returns a reference to the NodeMap of distances. |
---|
| 547 | /// |
---|
| 548 | /// Returns a reference to the NodeMap of distances. \pre \ref run() must |
---|
| 549 | /// be called before using this function. |
---|
| 550 | const DistMap &distMap() const { return *_dist;} |
---|
| 551 | |
---|
| 552 | /// \brief Returns a reference to the shortest path tree map. |
---|
| 553 | /// |
---|
| 554 | /// Returns a reference to the NodeMap of the edges of the |
---|
| 555 | /// shortest path tree. |
---|
| 556 | /// \pre \ref run() must be called before using this function. |
---|
| 557 | const PredMap &predMap() const { return *_pred; } |
---|
| 558 | |
---|
| 559 | /// \brief Checks if a node is reachable from the root. |
---|
| 560 | /// |
---|
| 561 | /// Returns \c true if \c v is reachable from the root. |
---|
| 562 | /// \pre \ref run() must be called before using this function. |
---|
| 563 | /// |
---|
| 564 | bool reached(Node v) { return (*_dist)[v] != OperationTraits::infinity(); } |
---|
| 565 | |
---|
| 566 | ///@} |
---|
| 567 | }; |
---|
| 568 | |
---|
| 569 | /// \brief Default traits class of BelmannFord function. |
---|
| 570 | /// |
---|
| 571 | /// Default traits class of BelmannFord function. |
---|
| 572 | /// \param _Graph Graph type. |
---|
| 573 | /// \param _LengthMap Type of length map. |
---|
| 574 | template <typename _Graph, typename _LengthMap> |
---|
| 575 | struct BelmannFordWizardDefaultTraits { |
---|
| 576 | /// \brief The graph type the algorithm runs on. |
---|
| 577 | typedef _Graph Graph; |
---|
| 578 | |
---|
| 579 | /// \brief The type of the map that stores the edge lengths. |
---|
| 580 | /// |
---|
| 581 | /// The type of the map that stores the edge lengths. |
---|
| 582 | /// It must meet the \ref concept::ReadMap "ReadMap" concept. |
---|
| 583 | typedef _LengthMap LengthMap; |
---|
| 584 | |
---|
| 585 | /// \brief The value type of the length map. |
---|
| 586 | typedef typename _LengthMap::Value Value; |
---|
| 587 | |
---|
| 588 | /// \brief Operation traits for belmann-ford algorithm. |
---|
| 589 | /// |
---|
| 590 | /// It defines the infinity type on the given Value type |
---|
| 591 | /// and the used operation. |
---|
| 592 | /// \see BelmannFordDefaultOperationTraits |
---|
| 593 | typedef BelmannFordDefaultOperationTraits<Value> OperationTraits; |
---|
| 594 | |
---|
| 595 | /// \brief The type of the map that stores the last |
---|
| 596 | /// edges of the shortest paths. |
---|
| 597 | /// |
---|
| 598 | /// The type of the map that stores the last |
---|
| 599 | /// edges of the shortest paths. |
---|
| 600 | /// It must meet the \ref concept::WriteMap "WriteMap" concept. |
---|
| 601 | typedef NullMap <typename _Graph::Node,typename _Graph::Edge> PredMap; |
---|
| 602 | |
---|
| 603 | /// \brief Instantiates a PredMap. |
---|
| 604 | /// |
---|
| 605 | /// This function instantiates a \ref PredMap. |
---|
| 606 | static PredMap *createPredMap(const _Graph &) { |
---|
| 607 | return new PredMap(); |
---|
| 608 | } |
---|
| 609 | /// \brief The type of the map that stores the dists of the nodes. |
---|
| 610 | /// |
---|
| 611 | /// The type of the map that stores the dists of the nodes. |
---|
| 612 | /// It must meet the \ref concept::WriteMap "WriteMap" concept. |
---|
| 613 | typedef NullMap<typename Graph::Node, Value> DistMap; |
---|
| 614 | /// \brief Instantiates a DistMap. |
---|
| 615 | /// |
---|
| 616 | /// This function instantiates a \ref DistMap. |
---|
| 617 | static DistMap *createDistMap(const _Graph &) { |
---|
| 618 | return new DistMap(); |
---|
| 619 | } |
---|
| 620 | }; |
---|
| 621 | |
---|
| 622 | /// \brief Default traits used by \ref BelmannFordWizard |
---|
| 623 | /// |
---|
| 624 | /// To make it easier to use BelmannFord algorithm |
---|
| 625 | /// we have created a wizard class. |
---|
| 626 | /// This \ref BelmannFordWizard class needs default traits, |
---|
| 627 | /// as well as the \ref BelmannFord class. |
---|
| 628 | /// The \ref BelmannFordWizardBase is a class to be the default traits of the |
---|
| 629 | /// \ref BelmannFordWizard class. |
---|
| 630 | /// \todo More named parameters are required... |
---|
| 631 | template<class _Graph,class _LengthMap> |
---|
| 632 | class BelmannFordWizardBase |
---|
| 633 | : public BelmannFordWizardDefaultTraits<_Graph,_LengthMap> { |
---|
| 634 | |
---|
| 635 | typedef BelmannFordWizardDefaultTraits<_Graph,_LengthMap> Base; |
---|
| 636 | protected: |
---|
| 637 | /// Type of the nodes in the graph. |
---|
| 638 | typedef typename Base::Graph::Node Node; |
---|
| 639 | |
---|
| 640 | /// Pointer to the underlying graph. |
---|
| 641 | void *_graph; |
---|
| 642 | /// Pointer to the length map |
---|
| 643 | void *_length; |
---|
| 644 | ///Pointer to the map of predecessors edges. |
---|
| 645 | void *_pred; |
---|
| 646 | ///Pointer to the map of distances. |
---|
| 647 | void *_dist; |
---|
| 648 | ///Pointer to the source node. |
---|
| 649 | Node _source; |
---|
| 650 | |
---|
| 651 | public: |
---|
| 652 | /// Constructor. |
---|
| 653 | |
---|
| 654 | /// This constructor does not require parameters, therefore it initiates |
---|
| 655 | /// all of the attributes to default values (0, INVALID). |
---|
| 656 | BelmannFordWizardBase() : _graph(0), _length(0), _pred(0), |
---|
| 657 | _dist(0), _source(INVALID) {} |
---|
| 658 | |
---|
| 659 | /// Constructor. |
---|
| 660 | |
---|
| 661 | /// This constructor requires some parameters, |
---|
| 662 | /// listed in the parameters list. |
---|
| 663 | /// Others are initiated to 0. |
---|
| 664 | /// \param graph is the initial value of \ref _graph |
---|
| 665 | /// \param length is the initial value of \ref _length |
---|
| 666 | /// \param source is the initial value of \ref _source |
---|
| 667 | BelmannFordWizardBase(const _Graph& graph, |
---|
| 668 | const _LengthMap& length, |
---|
| 669 | Node source = INVALID) : |
---|
| 670 | _graph((void *)&graph), _length((void *)&length), _pred(0), |
---|
| 671 | _dist(0), _source(source) {} |
---|
| 672 | |
---|
| 673 | }; |
---|
| 674 | |
---|
| 675 | /// A class to make the usage of BelmannFord algorithm easier |
---|
| 676 | |
---|
| 677 | /// This class is created to make it easier to use BelmannFord algorithm. |
---|
| 678 | /// It uses the functions and features of the plain \ref BelmannFord, |
---|
| 679 | /// but it is much simpler to use it. |
---|
| 680 | /// |
---|
| 681 | /// Simplicity means that the way to change the types defined |
---|
| 682 | /// in the traits class is based on functions that returns the new class |
---|
| 683 | /// and not on templatable built-in classes. |
---|
| 684 | /// When using the plain \ref BelmannFord |
---|
| 685 | /// the new class with the modified type comes from |
---|
| 686 | /// the original class by using the :: |
---|
| 687 | /// operator. In the case of \ref BelmannFordWizard only |
---|
| 688 | /// a function have to be called and it will |
---|
| 689 | /// return the needed class. |
---|
| 690 | /// |
---|
| 691 | /// It does not have own \ref run method. When its \ref run method is called |
---|
| 692 | /// it initiates a plain \ref BelmannFord class, and calls the \ref |
---|
| 693 | /// BelmannFord::run method of it. |
---|
| 694 | template<class _Traits> |
---|
| 695 | class BelmannFordWizard : public _Traits { |
---|
| 696 | typedef _Traits Base; |
---|
| 697 | |
---|
| 698 | ///The type of the underlying graph. |
---|
| 699 | typedef typename _Traits::Graph Graph; |
---|
| 700 | |
---|
| 701 | typedef typename Graph::Node Node; |
---|
| 702 | typedef typename Graph::NodeIt NodeIt; |
---|
| 703 | typedef typename Graph::Edge Edge; |
---|
| 704 | typedef typename Graph::OutEdgeIt EdgeIt; |
---|
| 705 | |
---|
| 706 | ///The type of the map that stores the edge lengths. |
---|
| 707 | typedef typename _Traits::LengthMap LengthMap; |
---|
| 708 | |
---|
| 709 | ///The type of the length of the edges. |
---|
| 710 | typedef typename LengthMap::Value Value; |
---|
| 711 | |
---|
| 712 | ///\brief The type of the map that stores the last |
---|
| 713 | ///edges of the shortest paths. |
---|
| 714 | typedef typename _Traits::PredMap PredMap; |
---|
| 715 | |
---|
| 716 | ///The type of the map that stores the dists of the nodes. |
---|
| 717 | typedef typename _Traits::DistMap DistMap; |
---|
| 718 | |
---|
| 719 | public: |
---|
| 720 | /// Constructor. |
---|
| 721 | BelmannFordWizard() : _Traits() {} |
---|
| 722 | |
---|
| 723 | /// \brief Constructor that requires parameters. |
---|
| 724 | /// |
---|
| 725 | /// Constructor that requires parameters. |
---|
| 726 | /// These parameters will be the default values for the traits class. |
---|
| 727 | BelmannFordWizard(const Graph& graph, const LengthMap& length, |
---|
| 728 | Node source = INVALID) |
---|
| 729 | : _Traits(graph, length, source) {} |
---|
| 730 | |
---|
| 731 | /// \brief Copy constructor |
---|
| 732 | BelmannFordWizard(const _Traits &b) : _Traits(b) {} |
---|
| 733 | |
---|
| 734 | ~BelmannFordWizard() {} |
---|
| 735 | |
---|
| 736 | /// \brief Runs BelmannFord algorithm from a given node. |
---|
| 737 | /// |
---|
| 738 | /// Runs BelmannFord algorithm from a given node. |
---|
| 739 | /// The node can be given by the \ref source function. |
---|
| 740 | void run() { |
---|
| 741 | if(Base::_source == INVALID) throw UninitializedParameter(); |
---|
| 742 | BelmannFord<Graph,LengthMap,_Traits> |
---|
| 743 | bf(*(Graph*)Base::_graph, *(LengthMap*)Base::_length); |
---|
| 744 | if (Base::_pred) bf.predMap(*(PredMap*)Base::_pred); |
---|
| 745 | if (Base::_dist) bf.distMap(*(DistMap*)Base::_dist); |
---|
| 746 | bf.run(Base::_source); |
---|
| 747 | } |
---|
| 748 | |
---|
| 749 | /// \brief Runs BelmannFord algorithm from the given node. |
---|
| 750 | /// |
---|
| 751 | /// Runs BelmannFord algorithm from the given node. |
---|
| 752 | /// \param s is the given source. |
---|
| 753 | void run(Node source) { |
---|
| 754 | Base::_source = source; |
---|
| 755 | run(); |
---|
| 756 | } |
---|
| 757 | |
---|
| 758 | template<class T> |
---|
| 759 | struct DefPredMapBase : public Base { |
---|
| 760 | typedef T PredMap; |
---|
| 761 | static PredMap *createPredMap(const Graph &) { return 0; }; |
---|
| 762 | DefPredMapBase(const _Traits &b) : _Traits(b) {} |
---|
| 763 | }; |
---|
| 764 | |
---|
| 765 | ///\brief \ref named-templ-param "Named parameter" |
---|
| 766 | ///function for setting PredMap type |
---|
| 767 | /// |
---|
| 768 | /// \ref named-templ-param "Named parameter" |
---|
| 769 | ///function for setting PredMap type |
---|
| 770 | /// |
---|
| 771 | template<class T> |
---|
| 772 | BelmannFordWizard<DefPredMapBase<T> > predMap(const T &t) |
---|
| 773 | { |
---|
| 774 | Base::_pred=(void *)&t; |
---|
| 775 | return BelmannFordWizard<DefPredMapBase<T> >(*this); |
---|
| 776 | } |
---|
| 777 | |
---|
| 778 | template<class T> |
---|
| 779 | struct DefDistMapBase : public Base { |
---|
| 780 | typedef T DistMap; |
---|
| 781 | static DistMap *createDistMap(const Graph &) { return 0; }; |
---|
| 782 | DefDistMapBase(const _Traits &b) : _Traits(b) {} |
---|
| 783 | }; |
---|
| 784 | |
---|
| 785 | ///\brief \ref named-templ-param "Named parameter" |
---|
| 786 | ///function for setting DistMap type |
---|
| 787 | /// |
---|
| 788 | /// \ref named-templ-param "Named parameter" |
---|
| 789 | ///function for setting DistMap type |
---|
| 790 | /// |
---|
| 791 | template<class T> |
---|
| 792 | BelmannFordWizard<DefDistMapBase<T> > distMap(const T &t) { |
---|
| 793 | Base::_dist=(void *)&t; |
---|
| 794 | return BelmannFordWizard<DefDistMapBase<T> >(*this); |
---|
| 795 | } |
---|
[1710] | 796 | |
---|
| 797 | template<class T> |
---|
| 798 | struct DefOperationTraitsBase : public Base { |
---|
| 799 | typedef T OperationTraits; |
---|
| 800 | DefOperationTraitsBase(const _Traits &b) : _Traits(b) {} |
---|
| 801 | }; |
---|
| 802 | |
---|
| 803 | ///\brief \ref named-templ-param "Named parameter" |
---|
| 804 | ///function for setting OperationTraits type |
---|
| 805 | /// |
---|
| 806 | /// \ref named-templ-param "Named parameter" |
---|
| 807 | ///function for setting OperationTraits type |
---|
| 808 | /// |
---|
| 809 | template<class T> |
---|
| 810 | BelmannFordWizard<DefOperationTraitsBase<T> > distMap() { |
---|
| 811 | return BelmannFordWizard<DefDistMapBase<T> >(*this); |
---|
| 812 | } |
---|
[1699] | 813 | |
---|
| 814 | /// \brief Sets the source node, from which the BelmannFord algorithm runs. |
---|
| 815 | /// |
---|
| 816 | /// Sets the source node, from which the BelmannFord algorithm runs. |
---|
| 817 | /// \param s is the source node. |
---|
| 818 | BelmannFordWizard<_Traits>& source(Node source) { |
---|
| 819 | Base::_source = source; |
---|
| 820 | return *this; |
---|
| 821 | } |
---|
| 822 | |
---|
| 823 | }; |
---|
| 824 | |
---|
| 825 | /// \brief Function type interface for BelmannFord algorithm. |
---|
| 826 | /// |
---|
| 827 | /// \ingroup flowalgs |
---|
| 828 | /// Function type interface for BelmannFord algorithm. |
---|
| 829 | /// |
---|
| 830 | /// This function also has several \ref named-templ-func-param |
---|
| 831 | /// "named parameters", they are declared as the members of class |
---|
| 832 | /// \ref BelmannFordWizard. |
---|
| 833 | /// The following |
---|
| 834 | /// example shows how to use these parameters. |
---|
| 835 | /// \code |
---|
| 836 | /// belmannford(g,length,source).predMap(preds).run(); |
---|
| 837 | /// \endcode |
---|
| 838 | /// \warning Don't forget to put the \ref BelmannFordWizard::run() "run()" |
---|
| 839 | /// to the end of the parameter list. |
---|
| 840 | /// \sa BelmannFordWizard |
---|
| 841 | /// \sa BelmannFord |
---|
| 842 | template<class _Graph, class _LengthMap> |
---|
| 843 | BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> > |
---|
| 844 | belmannFord(const _Graph& graph, |
---|
| 845 | const _LengthMap& length, |
---|
| 846 | typename _Graph::Node source = INVALID) { |
---|
| 847 | return BelmannFordWizard<BelmannFordWizardBase<_Graph,_LengthMap> > |
---|
| 848 | (graph, length, source); |
---|
| 849 | } |
---|
| 850 | |
---|
| 851 | } //END OF NAMESPACE LEMON |
---|
| 852 | |
---|
| 853 | #endif |
---|
| 854 | |
---|