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 //////////////////////////////////////////////////////////////////////
86 MTPGraph::MTPGraph(int nb_vertices, int nb_edges,
88 int source, int sink) {
89 _nb_vertices = nb_vertices;
92 _edges = new Edge[_nb_edges];
93 _vertices = new Vertex[_nb_vertices];
94 _front = new Vertex *[_nb_vertices];
95 _new_front = new Vertex *[_nb_vertices];
97 _source = &_vertices[source];
98 _sink = &_vertices[sink];
100 for(int v = 0; v < _nb_vertices; v++) {
104 for(int e = 0; e < nb_edges; e++) {
105 _vertices[from[e]].add_edge(_edges + e);
106 _edges[e].occupied = 0;
108 _edges[e].origin_vertex = _vertices + from[e];
109 _edges[e].terminal_vertex = _vertices + to[e];
116 MTPGraph::~MTPGraph() {
121 for(int p = 0; p < nb_paths; p++) delete paths[p];
125 //////////////////////////////////////////////////////////////////////
127 void MTPGraph::print(ostream *os) {
128 for(int k = 0; k < _nb_edges; k++) {
129 Edge *e = _edges + k;
130 (*os) << e->origin_vertex->id
132 << e->terminal_vertex->id
142 void MTPGraph::print_dot(ostream *os) {
143 (*os) << "digraph {" << endl;
144 // (*os) << " node [shape=circle];" << endl;
145 (*os) << " " << _source->id << " [peripheries=2];" << endl;
146 (*os) << " " << _sink->id << " [peripheries=2];" << endl;
147 for(int k = 0; k < _nb_edges; k++) {
148 Edge *e = _edges + k;
149 // (*os) << " " << e->origin_vertex->id << " -> " << e->terminal_vertex->id
153 (*os) << " " << e->origin_vertex->id << " -> " << e->terminal_vertex->id
154 << " [style=bold,color=black,label=\"" << e->length << "\"];" << endl;
156 (*os) << " " << e->origin_vertex->id << " -> " << e->terminal_vertex->id
157 << " [color=gray,label=\"" << e->length << "\"];" << endl;
160 (*os) << "}" << endl;
163 //////////////////////////////////////////////////////////////////////
165 void MTPGraph::initialize_positivized_lengths_with_min() {
166 scalar_t length_min = 0;
167 for(int n = 0; n < _nb_vertices; n++) {
168 for(Edge *e = _vertices[n].leaving_edges; e; e = e->next_leaving_edge) {
169 length_min = min(e->length, length_min);
172 for(int n = 0; n < _nb_vertices; n++) {
173 for(Edge *e = _vertices[n].leaving_edges; e; e = e->next_leaving_edge) {
174 e->positivized_length = e->length - length_min;
179 void MTPGraph::update_positivized_lengths() {
180 for(int k = 0; k < _nb_edges; k++) {
181 Edge *e = _edges + k;
182 e->positivized_length +=
183 e->origin_vertex->distance_from_source - e->terminal_vertex->distance_from_source;
187 void MTPGraph::force_positivized_lengths() {
189 scalar_t residual_error = 0.0;
190 scalar_t max_error = 0.0;
192 for(int n = 0; n < _nb_vertices; n++) {
193 for(Edge *e = _vertices[n].leaving_edges; e; e = e->next_leaving_edge) {
194 if(e->positivized_length < 0) {
196 residual_error -= e->positivized_length;
197 max_error = max(max_error, fabs(e->positivized_length));
199 e->positivized_length = 0.0;
204 cerr << "residual_error " << residual_error << " max_error " << residual_error << endl;
208 // This method does not change the edge occupation. It update
209 // distance_from_source and best_pred_edge_to_source.
210 void MTPGraph::find_shortest_path(Vertex **_front, Vertex **_new_front) {
217 for(int v = 0; v < _nb_vertices; v++) {
218 _vertices[v].distance_from_source = FLT_MAX;
219 _vertices[v].best_pred_edge_to_source = 0;
220 _vertices[v].iteration = 0;
225 int _front_size = 0, _new_front_size;
226 _front[_front_size++] = _source;
227 _source->distance_from_source = 0;
233 for(int f = 0; f < _front_size; f++) {
235 for(e = v->leaving_edges; e; e = e->next_leaving_edge) {
236 d = v->distance_from_source + e->positivized_length;
237 tv = e->terminal_vertex;
238 if(d < tv->distance_from_source) {
239 tv->distance_from_source = d;
240 tv->best_pred_edge_to_source = e;
241 if(tv->iteration < iteration) {
242 _new_front[_new_front_size++] = tv;
243 tv->iteration = iteration;
249 tmp_front = _new_front;
253 tmp_front_size = _new_front_size;
254 _new_front_size = _front_size;
255 _front_size = tmp_front_size;
256 } while(_front_size > 0);
259 void MTPGraph::find_best_paths(scalar_t *lengths) {
260 scalar_t total_length;
264 for(int e = 0; e < _nb_edges; e++) {
265 _edges[e].length = lengths[e];
266 _edges[e].occupied = 0;
267 _edges[e].positivized_length = _edges[e].length;
270 // We use one iteration of find_shortest_path simply to propagate
271 // the distance to make all the edge lengths positive.
272 find_shortest_path(_front, _new_front);
273 update_positivized_lengths();
276 // initialize_positivized_lengths_with_min();
279 force_positivized_lengths();
280 find_shortest_path(_front, _new_front);
281 update_positivized_lengths();
285 // Do we reach the _sink?
286 if(_sink->best_pred_edge_to_source) {
287 // If yes, compute the length of the best path
289 while(v->best_pred_edge_to_source) {
290 total_length += v->best_pred_edge_to_source->length;
291 v = v->best_pred_edge_to_source->origin_vertex;
293 // If that length is negative
294 if(total_length < 0.0) {
296 cerr << "Found a path of length " << total_length << endl;
298 // Invert all the edges along the best path
300 while(v->best_pred_edge_to_source) {
301 e = v->best_pred_edge_to_source;
302 v = e->origin_vertex;
304 // This is the only place where we change the occupations of
306 e->occupied = 1 - e->occupied;
311 } while(total_length < 0.0);
313 for(int k = 0; k < _nb_edges; k++) {
314 Edge *e = _edges + k;
315 if(e->occupied) { e->revert(); }
319 int MTPGraph::retrieve_one_path(Edge *e, int *nodes) {
323 if(nodes) { nodes[l++] = e->origin_vertex->id; }
326 while(e->terminal_vertex != _sink) {
327 if(nodes) { nodes[l++] = e->terminal_vertex->id; }
330 for(f = e->terminal_vertex->leaving_edges; f; f = f->next_leaving_edge) {
331 if(f->occupied) { nb_choices++; next = f; }
332 if(nb_choices == 0) {
333 cerr << "Non-sink path end point?!" << endl;
337 cerr << "Non node-disjoint path, can not retrieve." << endl;
344 if(nodes) { nodes[l++] = e->terminal_vertex->id; }
350 void MTPGraph::retrieve_disjoint_paths() {
353 for(int p = 0; p < nb_paths; p++) delete paths[p];
357 for(e = _source->leaving_edges; e; e = e->next_leaving_edge) {
358 if(e->occupied) { nb_paths++; }
361 paths = new Path *[nb_paths];
364 for(e = _source->leaving_edges; e; e = e->next_leaving_edge) {
366 int l = retrieve_one_path(e, 0);
367 paths[p] = new Path(l);
368 retrieve_one_path(e, paths[p]->nodes);