/*
- * mtp is the ``Multi Tracked Path'', an implementation of the
- * k-shortest path algorithm for multi-target tracking.
+ * mtp is the ``Multi Tracked Paths'', an implementation of the
+ * k-shortest paths algorithm for multi-target tracking.
*
* Copyright (c) 2012 Idiap Research Institute, http://www.idiap.ch/
* Written by Francois Fleuret <francois.fleuret@idiap.ch>
//////////////////////////////////////////////////////////////////////
MTPGraph::MTPGraph(int nb_vertices, int nb_edges,
- int *from, int *to,
+ int *vertex_from, int *vertex_to,
int source, int sink) {
_nb_vertices = nb_vertices;
_nb_edges = nb_edges;
_source = &_vertices[source];
_sink = &_vertices[sink];
- for(int v = 0; v < _nb_vertices; v++) {
- _vertices[v].id = v;
+ for(int k = 0; k < _nb_vertices; k++) {
+ _vertices[k].id = k;
}
for(int e = 0; e < nb_edges; e++) {
- _vertices[from[e]].add_leaving_edge(_edges + e);
+ _vertices[vertex_from[e]].add_leaving_edge(_edges + e);
_edges[e].occupied = 0;
_edges[e].id = e;
- _edges[e].origin_vertex = _vertices + from[e];
- _edges[e].terminal_vertex = _vertices + to[e];
+ _edges[e].origin_vertex = _vertices + vertex_from[e];
+ _edges[e].terminal_vertex = _vertices + vertex_to[e];
}
paths = 0;
void MTPGraph::print_dot(ostream *os) {
(*os) << "digraph {" << endl;
+ (*os) << " rankdir=\"LR\";" << endl;
(*os) << " node [shape=circle,width=0.75,fixedsize=true];" << endl;
(*os) << " edge [color=gray,arrowhead=open]" << endl;
(*os) << " " << _source->id << " [peripheries=2];" << endl;
(*os) << " " << _sink->id << " [peripheries=2];" << endl;
- // (*os) << " " << _source->id << " [style=bold,color=red];" << endl;
- // (*os) << " " << _sink->id << " [style=bold,color=green];" << endl;
for(int k = 0; k < _nb_edges; k++) {
Edge *e = _edges + k;
// (*os) << " " << e->origin_vertex->id << " -> " << e->terminal_vertex->id
#endif
}
-// This method does not change the edge occupation. It update
-// distance_from_source and pred_edge_toward_source.
+int MTPGraph::is_dag() {
+ Vertex *v, *tv;
+ Edge *e;
+
+ // We put everybody in the front
+ for(int k = 0; k < _nb_vertices; k++) {
+ _vertices[k].iteration = 0;
+ _front[k] = &_vertices[k];
+ }
+
+ int front_size = _nb_vertices, nb_with_incoming;
+ int iteration = 0;
+ int new_front_size, pred_front_size;
+
+ do {
+ iteration++;
+ nb_with_incoming = 0;
+
+ // We set the iteration field of all vertex with incoming edges to
+ // the current iteration value
+ for(int f = 0; f < front_size; f++) {
+ v = _front[f];
+ for(e = v->leaving_edges; e; e = e->next_leaving_edge) {
+ tv = e->terminal_vertex;
+ tv->iteration = iteration;
+ }
+ }
+
+ new_front_size = 0;
+ // We remove all the vertices without incoming edge
+ for(int f = 0; f < front_size; f++) {
+ v = _front[f];
+ if(v->iteration == iteration) {
+ _front[new_front_size++] = v;
+ }
+ }
+
+ pred_front_size = front_size;
+ front_size = new_front_size;
+ } while(front_size < pred_front_size);
+
+ return front_size == 0;
+}
+
+// This method does not change the edge occupation. It only set
+// properly for every vertex the fields distance_from_source and
+// pred_edge_toward_source.
+
void MTPGraph::find_shortest_path() {
Vertex **tmp_front;
int tmp_front_size;
Edge *e;
scalar_t d;
- for(int v = 0; v < _nb_vertices; v++) {
- _vertices[v].distance_from_source = FLT_MAX;
- _vertices[v].pred_edge_toward_source = 0;
- _vertices[v].iteration = 0;
+ for(int k = 0; k < _nb_vertices; k++) {
+ _vertices[k].distance_from_source = FLT_MAX;
+ _vertices[k].pred_edge_toward_source = 0;
+ _vertices[k].iteration = 0;
}
int iteration = 0;
- int _front_size = 0, _new_front_size;
- _front[_front_size++] = _source;
+ int front_size = 0, new_front_size;
+ _front[front_size++] = _source;
_source->distance_from_source = 0;
do {
- _new_front_size = 0;
+ new_front_size = 0;
iteration++;
- for(int f = 0; f < _front_size; f++) {
+ for(int f = 0; f < front_size; f++) {
v = _front[f];
for(e = v->leaving_edges; e; e = e->next_leaving_edge) {
d = v->distance_from_source + e->positivized_length;
tv->distance_from_source = d;
tv->pred_edge_toward_source = e;
if(tv->iteration < iteration) {
- _new_front[_new_front_size++] = tv;
+ _new_front[new_front_size++] = tv;
tv->iteration = iteration;
}
}
_new_front = _front;
_front = tmp_front;
- tmp_front_size = _new_front_size;
- _new_front_size = _front_size;
- _front_size = tmp_front_size;
- } while(_front_size > 0);
+ tmp_front_size = new_front_size;
+ new_front_size = front_size;
+ front_size = tmp_front_size;
+ } while(front_size > 0);
}
void MTPGraph::find_best_paths(scalar_t *lengths) {
_edges[e].positivized_length = _edges[e].length;
}
- // We use one iteration of find_shortest_path simply to propagate
- // the distance to make all the edge lengths positive.
+ // Let's be a bit paranoid
+ ASSERT(is_dag());
+
+ // We use call find_shortest_path here to set properly the distance,
+ // so that we can make all the edge lengths positive at the first
+ // iteration.
find_shortest_path();
do {
total_length = 0.0;
- // Do we reach the _sink?
+ // Do we reach the sink?
if(_sink->pred_edge_toward_source) {
// If yes, compute the length of the best path
v = _sink;
projects / mtp.git / blobdiff