X-Git-Url: https://www.fleuret.org/cgi-bin/gitweb/gitweb.cgi?a=blobdiff_plain;f=mtp_graph.cc;h=5371732a03e9c85e3b357f16464e36773535a0b7;hb=6c727bc27f1b594b5f3e5a756a0a01c3cb9b1cec;hp=49b97f7595c2d78fb37fe9ad93c751856c1f01e8;hpb=cdf649aeef318cc5c3dae231d9b1c16352d13515;p=mtp.git

diff --git a/mtp_graph.cc b/mtp_graph.cc
index 49b97f7..5371732 100644
--- a/mtp_graph.cc
+++ b/mtp_graph.cc
@@ -1,7 +1,7 @@
 
 /*
- *  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>
@@ -24,19 +24,18 @@
 
 #include "mtp_graph.h"
 
-#include <iostream>
 #include <float.h>
-#include <stdlib.h>
 
 using namespace std;
 
 class Edge {
 public:
-  int id, occupied;
+  int occupied;
   scalar_t length, positivized_length;
   Vertex *origin_vertex, *terminal_vertex;
 
-  // These are the links in the origin_vertex leaving edge list
+  // These fields are used for the linked list of a vertex's leaving
+  // edge list. We have to do insertions / deletions.
   Edge *next_leaving_edge, *pred_leaving_edge;
 
   inline void invert();
@@ -44,14 +43,15 @@ public:
 
 class Vertex {
 public:
-  int id;
   Edge *leaving_edges;
   scalar_t distance_from_source;
   Edge *pred_edge_toward_source;
 
-  int iteration; // Used in find_shortest_path to know if we already
-                 // added this vertex to the front
+  int last_change; // Used to mark which edges have already been
+                   // processed in some methods
+
   Vertex();
+
   inline void add_leaving_edge(Edge *e);
   inline void del_leaving_edge(Edge *e);
 };
@@ -60,7 +60,7 @@ public:
 
 void Edge::invert() {
   length = - length;
-  positivized_length = 0;
+  positivized_length = - positivized_length;
   origin_vertex->del_leaving_edge(this);
   terminal_vertex->add_leaving_edge(this);
   Vertex *t = terminal_vertex;
@@ -109,14 +109,9 @@ MTPGraph::MTPGraph(int nb_vertices, int nb_edges,
   _source = &_vertices[source];
   _sink = &_vertices[sink];
 
-  for(int v = 0; v < _nb_vertices; v++) {
-    _vertices[v].id = v;
-  }
-
   for(int e = 0; e < nb_edges; e++) {
     _vertices[vertex_from[e]].add_leaving_edge(_edges + e);
     _edges[e].occupied = 0;
-    _edges[e].id = e;
     _edges[e].origin_vertex = _vertices + vertex_from[e];
     _edges[e].terminal_vertex = _vertices + vertex_to[e];
   }
@@ -139,9 +134,9 @@ MTPGraph::~MTPGraph() {
 void MTPGraph::print(ostream *os) {
   for(int k = 0; k < _nb_edges; k++) {
     Edge *e = _edges + k;
-    (*os) << e->origin_vertex->id
+    (*os) << e->origin_vertex - _vertices
          << " -> "
-         << e->terminal_vertex->id
+         << e->terminal_vertex - _vertices
          << " "
          << e->length;
     if(e->occupied) {
@@ -153,18 +148,17 @@ void MTPGraph::print(ostream *os) {
 
 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;
+  (*os) << "        " << _source - _vertices << " [peripheries=2];" << endl;
+  (*os) << "        " << _sink - _vertices << " [peripheries=2];" << endl;
   for(int k = 0; k < _nb_edges; k++) {
     Edge *e = _edges + k;
-    // (*os) << "  " << e->origin_vertex->id << " -> " << e->terminal_vertex->id
-    // << ";"
-    // << endl;
-    (*os) << "        " << e->origin_vertex->id << " -> " << e->terminal_vertex->id
+    (*os) << "        "
+          << e->origin_vertex - _vertices
+          << " -> "
+          << e->terminal_vertex - _vertices
           << " [";
     if(e->occupied) {
       (*os) << "style=bold,color=black,";
@@ -189,15 +183,25 @@ void MTPGraph::force_positivized_lengths() {
   scalar_t residual_error = 0.0;
   scalar_t max_error = 0.0;
 #endif
-  for(int n = 0; n < _nb_vertices; n++) {
-    for(Edge *e = _vertices[n].leaving_edges; e; e = e->next_leaving_edge) {
-      if(e->positivized_length < 0) {
+  for(int k = 0; k < _nb_edges; k++) {
+    Edge *e = _edges + k;
+
+    if(e->positivized_length < 0) {
+
 #ifdef VERBOSE
+      if((e->origin_vertex->last_change < 0 && e->terminal_vertex->last_change >= 0) ||
+         (e->origin_vertex->last_change >= 0 && e->terminal_vertex->last_change < 0)) {
+        cout << "Inconsistent non-connexity (this should never happen)." << endl;
+        abort();
+      }
+      if(e->origin_vertex->last_change >= 0 &&
+         e->terminal_vertex->last_change >= 0 &&
+         e->positivized_length < 0) {
         residual_error -= e->positivized_length;
         max_error = max(max_error, - e->positivized_length);
-#endif
-        e->positivized_length = 0.0;
       }
+#endif
+      e->positivized_length = 0.0;
     }
   }
 #ifdef VERBOSE
@@ -205,32 +209,83 @@ void MTPGraph::force_positivized_lengths() {
 #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;
+  Edge *e;
+
+  // We put everybody in the front
+  for(int k = 0; k < _nb_vertices; k++) {
+    _vertices[k].last_change = -1;
+    _front[k] = &_vertices[k];
+  }
+
+  int iteration = 0;
+  int front_size = _nb_vertices, pred_front_size;
+
+  do {
+    // We set the last_change field of all the vertices 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) {
+        e->terminal_vertex->last_change = iteration;
+      }
+    }
+
+    pred_front_size = front_size;
+    front_size = 0;
+
+    // We keep all the vertices with incoming nodes
+    for(int f = 0; f < pred_front_size; f++) {
+      v = _front[f];
+      if(v->last_change == iteration) {
+        _front[front_size++] = v;
+      }
+    }
+
+    iteration++;
+  } 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;
   Vertex *v, *tv;
   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;
+#ifdef DEBUG
+  if(is_dag()) {
+    cout << "find_shortest_path: DAG -> ok" << endl;
+  } else {
+    for(int e = 0; e < _nb_edges; e++) {
+      if(_edges[e].positivized_length < 0)  abort();
+    }
+    cout << "find_shortest_path: All positivized_length are positive -> ok" << endl;
+  }
+#endif
+
+  for(int k = 0; k < _nb_vertices; k++) {
+    _vertices[k].distance_from_source = FLT_MAX;
+    _vertices[k].pred_edge_toward_source = 0;
+    _vertices[k].last_change = -1;
   }
 
   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;
-    iteration++;
+    new_front_size = 0;
 
-    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;
@@ -238,22 +293,20 @@ void MTPGraph::find_shortest_path() {
         if(d < tv->distance_from_source) {
           tv->distance_from_source = d;
           tv->pred_edge_toward_source = e;
-          if(tv->iteration < iteration) {
-            _new_front[_new_front_size++] = tv;
-            tv->iteration = iteration;
+          if(tv->last_change < iteration) {
+            _new_front[new_front_size++] = tv;
+            tv->last_change = iteration;
           }
         }
       }
     }
 
-    tmp_front = _new_front;
-    _new_front = _front;
-    _front = tmp_front;
+    tmp_front = _new_front; _new_front = _front; _front = tmp_front;
+
+    front_size = new_front_size;
 
-    tmp_front_size = _new_front_size;
-    _new_front_size = _front_size;
-    _front_size = tmp_front_size;
-  } while(_front_size > 0);
+    iteration++;
+  } while(front_size > 0);
 }
 
 void MTPGraph::find_best_paths(scalar_t *lengths) {
@@ -267,8 +320,9 @@ 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.
+  // We call find_shortest_path here to set properly the distances to
+  // the source, so that we can make all the edge lengths positive at
+  // the first iteration.
   find_shortest_path();
 
   do {
@@ -278,9 +332,10 @@ void MTPGraph::find_best_paths(scalar_t *lengths) {
 
     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
+      // If yes, compute the length of the best path according to the
+      // original edge lengths
       v = _sink;
       while(v->pred_edge_toward_source) {
         total_length += v->pred_edge_toward_source->length;
@@ -309,42 +364,48 @@ void MTPGraph::find_best_paths(scalar_t *lengths) {
   // Put back the graph in its original state (i.e. invert edges which
   // have been inverted in the process)
   for(int k = 0; k < _nb_edges; k++) {
-    Edge *e = _edges + k;
+    e = _edges + k;
     if(e->occupied) { e->invert(); }
   }
 }
 
 int MTPGraph::retrieve_one_path(Edge *e, Path *path) {
   Edge *f, *next = 0;
-  int l = 0;
+  int l = 0, nb_occupied_next;
 
   if(path) {
-    path->nodes[l++] = e->origin_vertex->id;
+    path->nodes[l++] = e->origin_vertex - _vertices;
     path->length = e->length;
   } else l++;
 
   while(e->terminal_vertex != _sink) {
     if(path) {
-      path->nodes[l++] = e->terminal_vertex->id;
+      path->nodes[l++] = e->terminal_vertex - _vertices;
       path->length += e->length;
     } else l++;
-    int nb_choices = 0;
+
+    nb_occupied_next = 0;
     for(f = e->terminal_vertex->leaving_edges; f; f = f->next_leaving_edge) {
-      if(f->occupied) { nb_choices++; next = f; }
-      if(nb_choices == 0) {
-        cerr << "retrieve_one_path: Non-sink end point." << endl;
-        abort();
-      }
-      if(nb_choices > 1) {
-        cerr << "retrieve_one_path: Non node-disjoint paths." << endl;
-        abort();
-      }
+      if(f->occupied) { nb_occupied_next++; next = f; }
     }
+
+#ifdef DEBUG
+    if(nb_occupied_next == 0) {
+      cerr << "retrieve_one_path: Non-sink end point." << endl;
+      abort();
+    }
+
+    else if(nb_occupied_next > 1) {
+      cerr << "retrieve_one_path: Non node-disjoint paths." << endl;
+      abort();
+    }
+#endif
+
     e = next;
   }
 
   if(path) {
-    path->nodes[l++] = e->terminal_vertex->id;
+    path->nodes[l++] = e->terminal_vertex - _vertices;
     path->length += e->length;
   } else l++;
 
@@ -353,6 +414,7 @@ int MTPGraph::retrieve_one_path(Edge *e, Path *path) {
 
 void MTPGraph::retrieve_disjoint_paths() {
   Edge *e;
+  int p, l;
 
   for(int p = 0; p < nb_paths; p++) delete paths[p];
   delete[] paths;
@@ -364,10 +426,10 @@ void MTPGraph::retrieve_disjoint_paths() {
 
   paths = new Path *[nb_paths];
 
-  int p = 0;
+  p = 0;
   for(e = _source->leaving_edges; e; e = e->next_leaving_edge) {
     if(e->occupied) {
-      int l = retrieve_one_path(e, 0);
+      l = retrieve_one_path(e, 0);
       paths[p] = new Path(l);
       retrieve_one_path(e, paths[p]);
       p++;