2 ///////////////////////////////////////////////////////////////////////////
3 // This program is free software: you can redistribute it and/or modify //
4 // it under the terms of the version 3 of the GNU General Public License //
5 // as published by the Free Software Foundation. //
7 // This program is distributed in the hope that it will be useful, but //
8 // WITHOUT ANY WARRANTY; without even the implied warranty of //
9 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU //
10 // General Public License for more details. //
12 // You should have received a copy of the GNU General Public License //
13 // along with this program. If not, see <http://www.gnu.org/licenses/>. //
15 // Written by and Copyright (C) Francois Fleuret //
16 // Contact <francois.fleuret@idiap.ch> for comments & bug reports //
17 ///////////////////////////////////////////////////////////////////////////
19 #include "mtp_graph.h"
30 scalar_t length, positivized_length;
31 Vertex *origin_vertex, *terminal_vertex;
33 // These are the links in the origin_vertex leaving edge list
34 Edge *next_leaving_edge, *pred_leaving_edge;
43 scalar_t distance_from_source;
44 Edge *best_pred_edge_to_source;
46 int iteration; // Used in find_shortest_path to know if we already
47 // added this vertex to the front
49 inline void add_edge(Edge *e);
50 inline void del_edge(Edge *e);
53 //////////////////////////////////////////////////////////////////////
57 positivized_length = 0;
58 origin_vertex->del_edge(this);
59 terminal_vertex->add_edge(this);
60 Vertex *t = terminal_vertex;
61 terminal_vertex = origin_vertex;
65 //////////////////////////////////////////////////////////////////////
71 void Vertex::add_edge(Edge *e) {
72 e->next_leaving_edge = leaving_edges;
73 e->pred_leaving_edge = 0;
74 if(leaving_edges) { leaving_edges->pred_leaving_edge = e; }
78 void Vertex::del_edge(Edge *e) {
79 if(e == leaving_edges) { leaving_edges = e->next_leaving_edge; }
80 if(e->pred_leaving_edge) { e->pred_leaving_edge->next_leaving_edge = e->next_leaving_edge; }
81 if(e->next_leaving_edge) { e->next_leaving_edge->pred_leaving_edge = e->pred_leaving_edge; }
84 //////////////////////////////////////////////////////////////////////
88 nodes = new int[length];
95 //////////////////////////////////////////////////////////////////////
97 MTPGraph::MTPGraph(int nb_vertices, int nb_edges,
99 int source, int sink) {
100 _nb_vertices = nb_vertices;
101 _nb_edges = nb_edges;
103 _edges = new Edge[_nb_edges];
104 _vertices = new Vertex[_nb_vertices];
105 _front = new Vertex *[_nb_vertices];
106 _new_front = new Vertex *[_nb_vertices];
108 _source = &_vertices[source];
109 _sink = &_vertices[sink];
111 for(int v = 0; v < _nb_vertices; v++) {
115 for(int e = 0; e < nb_edges; e++) {
116 _vertices[from[e]].add_edge(_edges + e);
117 _edges[e].occupied = 0;
119 _edges[e].origin_vertex = _vertices + from[e];
120 _edges[e].terminal_vertex = _vertices + to[e];
127 MTPGraph::~MTPGraph() {
132 for(int p = 0; p < nb_paths; p++) delete paths[p];
136 //////////////////////////////////////////////////////////////////////
138 void MTPGraph::print(ostream *os) {
139 for(int k = 0; k < _nb_edges; k++) {
140 Edge *e = _edges + k;
141 (*os) << e->origin_vertex->id
143 << e->terminal_vertex->id
153 void MTPGraph::print_dot(ostream *os) {
154 (*os) << "digraph {" << endl;
155 (*os) << " node[shape=circle];" << endl;
156 for(int k = 0; k < _nb_edges; k++) {
157 Edge *e = _edges + k;
158 // (*os) << " " << e->origin_vertex->id << " -> " << e->terminal_vertex->id
162 (*os) << " " << e->origin_vertex->id << " -> " << e->terminal_vertex->id
163 << " [style=bold,color=black,label=\"" << e->length << "\"];" << endl;
165 (*os) << " " << e->origin_vertex->id << " -> " << e->terminal_vertex->id
166 << " [color=gray,label=\"" << e->length << "\"];" << endl;
169 (*os) << "}" << endl;
172 //////////////////////////////////////////////////////////////////////
174 void MTPGraph::initialize_positivized_lengths_with_min() {
175 scalar_t length_min = 0;
176 for(int n = 0; n < _nb_vertices; n++) {
177 for(Edge *e = _vertices[n].leaving_edges; e; e = e->next_leaving_edge) {
178 length_min = min(e->length, length_min);
181 for(int n = 0; n < _nb_vertices; n++) {
182 for(Edge *e = _vertices[n].leaving_edges; e; e = e->next_leaving_edge) {
183 e->positivized_length = e->length - length_min;
188 void MTPGraph::update_positivized_lengths() {
189 for(int k = 0; k < _nb_edges; k++) {
190 Edge *e = _edges + k;
191 e->positivized_length +=
192 e->origin_vertex->distance_from_source - e->terminal_vertex->distance_from_source;
196 void MTPGraph::force_positivized_lengths() {
198 scalar_t residual_error = 0.0;
199 scalar_t max_error = 0.0;
201 for(int n = 0; n < _nb_vertices; n++) {
202 for(Edge *e = _vertices[n].leaving_edges; e; e = e->next_leaving_edge) {
203 if(e->positivized_length < 0) {
205 residual_error -= e->positivized_length;
206 max_error = max(max_error, fabs(e->positivized_length));
208 e->positivized_length = 0.0;
213 cerr << "residual_error " << residual_error << " max_error " << residual_error << endl;
217 // This method does not change the edge occupation. It update
218 // distance_from_source and best_pred_edge_to_source.
219 void MTPGraph::find_shortest_path(Vertex **_front, Vertex **_new_front) {
226 for(int v = 0; v < _nb_vertices; v++) {
227 _vertices[v].distance_from_source = FLT_MAX;
228 _vertices[v].best_pred_edge_to_source = 0;
229 _vertices[v].iteration = 0;
234 int _front_size = 0, _new_front_size;
235 _front[_front_size++] = _source;
236 _source->distance_from_source = 0;
242 for(int f = 0; f < _front_size; f++) {
244 for(e = v->leaving_edges; e; e = e->next_leaving_edge) {
245 d = v->distance_from_source + e->positivized_length;
246 tv = e->terminal_vertex;
247 if(d < tv->distance_from_source) {
248 tv->distance_from_source = d;
249 tv->best_pred_edge_to_source = e;
250 if(tv->iteration < iteration) {
251 _new_front[_new_front_size++] = tv;
252 tv->iteration = iteration;
258 tmp_front = _new_front;
262 tmp_front_size = _new_front_size;
263 _new_front_size = _front_size;
264 _front_size = tmp_front_size;
265 } while(_front_size > 0);
268 void MTPGraph::find_best_paths(scalar_t *lengths) {
269 scalar_t total_length;
273 for(int e = 0; e < _nb_edges; e++) {
274 _edges[e].length = lengths[e];
275 _edges[e].occupied = 0;
276 _edges[e].positivized_length = _edges[e].length;
279 // We use one iteration of find_shortest_path simply to propagate
280 // the distance to make all the edge lengths positive.
281 find_shortest_path(_front, _new_front);
282 update_positivized_lengths();
285 // initialize_positivized_lengths_with_min();
288 force_positivized_lengths();
289 find_shortest_path(_front, _new_front);
290 update_positivized_lengths();
294 // Do we reach the _sink?
295 if(_sink->best_pred_edge_to_source) {
296 // If yes, compute the length of the best path
298 while(v->best_pred_edge_to_source) {
299 total_length += v->best_pred_edge_to_source->length;
300 v = v->best_pred_edge_to_source->origin_vertex;
302 // If that length is negative
303 if(total_length < 0.0) {
305 cerr << "Found a path of length " << total_length << endl;
307 // Invert all the edges along the best path
309 while(v->best_pred_edge_to_source) {
310 e = v->best_pred_edge_to_source;
311 v = e->origin_vertex;
313 // This is the only place where we change the occupations of
315 e->occupied = 1 - e->occupied;
320 } while(total_length < 0.0);
322 for(int k = 0; k < _nb_edges; k++) {
323 Edge *e = _edges + k;
324 if(e->occupied) { e->revert(); }
328 int MTPGraph::retrieve_one_path(Edge *e, int *nodes) {
332 if(nodes) { nodes[l++] = e->origin_vertex->id; }
335 while(e->terminal_vertex != _sink) {
336 if(nodes) { nodes[l++] = e->terminal_vertex->id; }
339 for(f = e->terminal_vertex->leaving_edges; f; f = f->next_leaving_edge) {
340 if(f->occupied) { nb_choices++; next = f; }
341 if(nb_choices == 0) {
342 cerr << "Non-sink path end point?!" << endl;
346 cerr << "Non node-disjoint path, can not retrieve." << endl;
353 if(nodes) { nodes[l++] = e->terminal_vertex->id; }
359 void MTPGraph::retrieve_disjoint_paths() {
362 for(int p = 0; p < nb_paths; p++) delete paths[p];
366 for(e = _source->leaving_edges; e; e = e->next_leaving_edge) {
367 if(e->occupied) { nb_paths++; }
370 paths = new Path *[nb_paths];
373 for(e = _source->leaving_edges; e; e = e->next_leaving_edge) {
375 int l = retrieve_one_path(e, 0);
376 paths[p] = new Path(l);
377 retrieve_one_path(e, paths[p]->nodes);