2 ///////////////////////////////////////////////////////////////////////////
5 // This program is free software: you can redistribute it and/or modify //
6 // it under the terms of the version 3 of the GNU General Public License //
7 // as published by the Free Software Foundation. //
9 // This program is distributed in the hope that it will be useful, but //
10 // WITHOUT ANY WARRANTY; without even the implied warranty of //
11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU //
12 // General Public License for more details. //
14 // You should have received a copy of the GNU General Public License //
15 // along with this program. If not, see <http://www.gnu.org/licenses/>. //
17 // Written by and Copyright (C) Francois Fleuret //
18 // Contact <francois.fleuret@idiap.ch> for comments & bug reports //
21 ///////////////////////////////////////////////////////////////////////////
34 typedef float scalar_t;
37 #define ASSERT(x) if(!(x)) { \
38 std::cerr << "ASSERT FAILED IN " << __FILE__ << ":" << __LINE__ << endl; \
45 void raise_es(int nb_edges, scalar_t *el) {
46 scalar_t min_es = el[0];
47 for(int e = 1; e < nb_edges; e++) {
48 min_es = min(min_es, el[e]);
50 for(int e = 0; e < nb_edges; e++) {
55 void add_dpsi_es(int nb_edges, scalar_t *el, int *ea, int *eb, scalar_t *psi) {
56 for(int e = 0; e < nb_edges; e++) {
57 el[e] += psi[ea[e]] - psi[eb[e]];
61 void find_shortest(int nb_vertices,
62 int nb_edges, scalar_t *el, int *ea, int *eb,
64 int *edge_back, scalar_t *dist) {
65 for(int v = 0; v < nb_vertices; v++) {
72 for(int v = 0; v < nb_vertices; v++) {
76 for(int e = 0; e < nb_edges; e++) {
84 for(int e = 0; e < nb_edges; e++) {
85 d = dist[ea[e]] + el[e];
92 } while(nb_changes > 0);
95 void find_best_paths(int nb_vertices,
96 int nb_edges, scalar_t *el, int *ea, int *eb,
98 int *edge_occupation) {
99 scalar_t *dist = new scalar_t[nb_vertices];
100 int *edge_back = new int[nb_vertices];
101 scalar_t *tmp_el = new scalar_t[nb_edges];
103 for(int e = 0; e < nb_edges; e++) {
105 edge_occupation[e] = 0;
108 raise_es(nb_edges, tmp_el);
112 find_shortest(nb_vertices, nb_edges, tmp_el, ea, eb, source, sink, edge_back, dist);
113 add_dpsi_es(nb_edges, tmp_el, ea, eb, dist);
115 if(edge_back[sink] >= 0) {
118 int e = edge_back[v];
122 cout << "INVERTING " << ea[e] << " -> " << eb[e] << " [" << el[e] << "]" << endl;
128 tmp_el[e] = - tmp_el[e];
129 edge_occupation[e] = 1 - edge_occupation[e];
132 cout << "FOUND A PATH OF LENGTH " << s << endl;
142 int main(int argc, char **argv) {
145 cerr << argv[0] << " <graph file>" << endl;
149 ifstream file(argv[1]);
151 int nb_edges, nb_vertices;
155 file >> nb_vertices >> nb_edges;
156 file >> source >> sink;
158 cout << "nb_edges = " << nb_edges << endl;
159 cout << "nb_vertices = " << nb_vertices << endl;
160 cout << "source = " << source << endl;
161 cout << "sink = " << sink << endl;
163 scalar_t *el = new scalar_t[nb_edges];
164 int *ea = new int[nb_edges];
165 int *eb = new int[nb_edges];
166 int *edge_occupation = new int[nb_edges];
168 for(int e = 0; e < nb_edges; e++) {
169 file >> ea[e] >> eb[e] >> el[e];
171 cout << ea[e] << " -> " << eb[e] << " [" << el[e] << "]" << endl;
175 find_best_paths(nb_vertices, nb_edges, el, ea, eb, source, sink,
178 for(int e = 0; e < nb_edges; e++) {
179 if(edge_occupation[e]) {
180 cout << ea[e] << " " << eb[e] << endl;
184 delete[] edge_occupation;
191 cerr << "Can not open " << argv[1] << endl;