X-Git-Url: https://www.fleuret.org/cgi-bin/gitweb/gitweb.cgi?p=mtp.git;a=blobdiff_plain;f=mtp_graph.cc;h=95ef485d5166579153e68209dd90a97ab5b1b76c;hp=a60e532587bca4cb184a855abd629e6cbc8a2023;hb=342c65f1c9deda8de361227afe26c7cd8b46d7c2;hpb=6e7fbc025b89997ae663bda0696eca80a6d3f93b

diff --git a/mtp_graph.cc b/mtp_graph.cc
index a60e532..95ef485 100644
--- a/mtp_graph.cc
+++ b/mtp_graph.cc
@@ -1,20 +1,26 @@
 
-///////////////////////////////////////////////////////////////////////////
-// This program is free software: you can redistribute it and/or modify  //
-// it under the terms of the version 3 of the GNU General Public License //
-// as published by the Free Software Foundation.                         //
-//                                                                       //
-// This program is distributed in the hope that it will be useful, but   //
-// WITHOUT ANY WARRANTY; without even the implied warranty of            //
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU      //
-// General Public License for more details.                              //
-//                                                                       //
-// You should have received a copy of the GNU General Public License     //
-// along with this program. If not, see <http://www.gnu.org/licenses/>.  //
-//                                                                       //
-// Written by and Copyright (C) Francois Fleuret                         //
-// Contact <francois.fleuret@idiap.ch> for comments & bug reports        //
-///////////////////////////////////////////////////////////////////////////
+/*
+ *  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>
+ *
+ *  This file is part of mtp.
+ *
+ *  mtp is free software: you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 3 as
+ *  published by the Free Software Foundation.
+ *
+ *  mtp is distributed in the hope that it will be useful, but WITHOUT
+ *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ *  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+ *  License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with selector.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
 
 #include "mtp_graph.h"
 
@@ -41,13 +47,13 @@ public:
   int id;
   Edge *leaving_edges;
   scalar_t distance_from_source;
-  Edge *best_pred_edge_to_source;
+  Edge *pred_edge_toward_source;
 
   int iteration; // Used in find_shortest_path to know if we already
                  // added this vertex to the front
   Vertex();
-  inline void add_edge(Edge *e);
-  inline void del_edge(Edge *e);
+  inline void add_leaving_edge(Edge *e);
+  inline void del_leaving_edge(Edge *e);
 };
 
 //////////////////////////////////////////////////////////////////////
@@ -55,8 +61,8 @@ public:
 void Edge::invert() {
   length = - length;
   positivized_length = 0;
-  origin_vertex->del_edge(this);
-  terminal_vertex->add_edge(this);
+  origin_vertex->del_leaving_edge(this);
+  terminal_vertex->add_leaving_edge(this);
   Vertex *t = terminal_vertex;
   terminal_vertex = origin_vertex;
   origin_vertex = t;
@@ -68,23 +74,29 @@ Vertex::Vertex() {
   leaving_edges = 0;
 }
 
-void Vertex::add_edge(Edge *e) {
+void Vertex::add_leaving_edge(Edge *e) {
   e->next_leaving_edge = leaving_edges;
   e->pred_leaving_edge = 0;
   if(leaving_edges) { leaving_edges->pred_leaving_edge = e; }
   leaving_edges = e;
 }
 
-void Vertex::del_edge(Edge *e) {
-  if(e == leaving_edges) { leaving_edges = e->next_leaving_edge; }
-  if(e->pred_leaving_edge) { e->pred_leaving_edge->next_leaving_edge = e->next_leaving_edge; }
-  if(e->next_leaving_edge) { e->next_leaving_edge->pred_leaving_edge = e->pred_leaving_edge; }
+void Vertex::del_leaving_edge(Edge *e) {
+  if(e == leaving_edges) {
+    leaving_edges = e->next_leaving_edge;
+  }
+  if(e->pred_leaving_edge) {
+    e->pred_leaving_edge->next_leaving_edge = e->next_leaving_edge;
+  }
+  if(e->next_leaving_edge) {
+    e->next_leaving_edge->pred_leaving_edge = e->pred_leaving_edge;
+  }
 }
 
 //////////////////////////////////////////////////////////////////////
 
 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;
@@ -97,16 +109,16 @@ 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 k = 0; k < _nb_vertices; k++) {
+    _vertices[k].id = k;
   }
 
   for(int e = 0; e < nb_edges; e++) {
-    _vertices[from[e]].add_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;
@@ -141,42 +153,28 @@ void MTPGraph::print(ostream *os) {
 
 void MTPGraph::print_dot(ostream *os) {
   (*os) << "digraph {" << endl;
-  // (*os) << "        node [shape=circle];" << endl;
-  (*os) << "        edge [color=gray]" << 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;
   for(int k = 0; k < _nb_edges; k++) {
     Edge *e = _edges + k;
     // (*os) << "  " << e->origin_vertex->id << " -> " << e->terminal_vertex->id
-          // << ";"
-          // << endl;
+    // << ";"
+    // << endl;
+    (*os) << "        " << e->origin_vertex->id << " -> " << e->terminal_vertex->id
+          << " [";
     if(e->occupied) {
-      (*os) << "        " << e->origin_vertex->id << " -> " << e->terminal_vertex->id
-           << " [style=bold,color=black,label=\"" << e->length << "\"];" << endl;
-    } else {
-      (*os) << "        " << e->origin_vertex->id << " -> " << e->terminal_vertex->id
-           << " [label=\"" << e->length << "\"];" << endl;
+      (*os) << "style=bold,color=black,";
     }
+    (*os) << "label=\"" << e->length << "\"];" << endl;
   }
   (*os) << "}" << endl;
 }
 
 //////////////////////////////////////////////////////////////////////
 
-void MTPGraph::initialize_positivized_lengths_with_min() {
-  scalar_t length_min = 0;
-  for(int n = 0; n < _nb_vertices; n++) {
-    for(Edge *e = _vertices[n].leaving_edges; e; e = e->next_leaving_edge) {
-      length_min = min(e->length, length_min);
-    }
-  }
-  for(int n = 0; n < _nb_vertices; n++) {
-    for(Edge *e = _vertices[n].leaving_edges; e; e = e->next_leaving_edge) {
-      e->positivized_length = e->length - length_min;
-    }
-  }
-}
-
 void MTPGraph::update_positivized_lengths() {
   for(int k = 0; k < _nb_edges; k++) {
     Edge *e = _edges + k;
@@ -195,7 +193,7 @@ void MTPGraph::force_positivized_lengths() {
       if(e->positivized_length < 0) {
 #ifdef VERBOSE
         residual_error -= e->positivized_length;
-        max_error = max(max_error, fabs(e->positivized_length));
+        max_error = max(max_error, - e->positivized_length);
 #endif
         e->positivized_length = 0.0;
       }
@@ -206,41 +204,87 @@ void MTPGraph::force_positivized_lengths() {
 #endif
 }
 
-// This method does not change the edge occupation. It update
-// distance_from_source and best_pred_edge_to_source.
-void MTPGraph::find_shortest_path(Vertex **_front, Vertex **_new_front) {
+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;
   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].best_pred_edge_to_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 = e->terminal_vertex;
         if(d < tv->distance_from_source) {
           tv->distance_from_source = d;
-          tv->best_pred_edge_to_source = e;
+          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;
           }
         }
@@ -251,10 +295,10 @@ void MTPGraph::find_shortest_path(Vertex **_front, Vertex **_new_front) {
     _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) {
@@ -268,28 +312,28 @@ 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.
-  find_shortest_path(_front, _new_front);
-  update_positivized_lengths();
+  // Let's be a bit paranoid
+  ASSERT(is_dag());
 
-  // #warning
-  // initialize_positivized_lengths_with_min();
+  // 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 {
-    force_positivized_lengths();
-    find_shortest_path(_front, _new_front);
     update_positivized_lengths();
+    force_positivized_lengths();
+    find_shortest_path();
 
     total_length = 0.0;
 
-    // Do we reach the _sink?
-    if(_sink->best_pred_edge_to_source) {
+    // Do we reach the sink?
+    if(_sink->pred_edge_toward_source) {
       // If yes, compute the length of the best path
       v = _sink;
-      while(v->best_pred_edge_to_source) {
-        total_length += v->best_pred_edge_to_source->length;
-        v = v->best_pred_edge_to_source->origin_vertex;
+      while(v->pred_edge_toward_source) {
+        total_length += v->pred_edge_toward_source->length;
+        v = v->pred_edge_toward_source->origin_vertex;
       }
       // If that length is negative
       if(total_length < 0.0) {
@@ -298,8 +342,8 @@ void MTPGraph::find_best_paths(scalar_t *lengths) {
 #endif
         // Invert all the edges along the best path
         v = _sink;
-        while(v->best_pred_edge_to_source) {
-          e = v->best_pred_edge_to_source;
+        while(v->pred_edge_toward_source) {
+          e = v->pred_edge_toward_source;
           v = e->origin_vertex;
           e->invert();
           // This is the only place where we change the occupations of
@@ -311,39 +355,47 @@ void MTPGraph::find_best_paths(scalar_t *lengths) {
 
   } while(total_length < 0.0);
 
+  // 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;
     if(e->occupied) { e->invert(); }
   }
 }
 
-int MTPGraph::retrieve_one_path(Edge *e, int *nodes) {
+int MTPGraph::retrieve_one_path(Edge *e, Path *path) {
   Edge *f, *next = 0;
   int l = 0;
 
-  if(nodes) { nodes[l++] = e->origin_vertex->id; }
-  else l++;
+  if(path) {
+    path->nodes[l++] = e->origin_vertex->id;
+    path->length = e->length;
+  } else l++;
 
   while(e->terminal_vertex != _sink) {
-    if(nodes) { nodes[l++] = e->terminal_vertex->id; }
-    else l++;
+    if(path) {
+      path->nodes[l++] = e->terminal_vertex->id;
+      path->length += e->length;
+    } else l++;
     int nb_choices = 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 << "Non-sink path end point?!" << endl;
+        cerr << "retrieve_one_path: Non-sink end point." << endl;
         abort();
       }
       if(nb_choices > 1) {
-        cerr << "Non node-disjoint path, can not retrieve." << endl;
+        cerr << "retrieve_one_path: Non node-disjoint paths." << endl;
         abort();
       }
     }
     e = next;
   }
 
-  if(nodes) { nodes[l++] = e->terminal_vertex->id; }
-  else l++;
+  if(path) {
+    path->nodes[l++] = e->terminal_vertex->id;
+    path->length += e->length;
+  } else l++;
 
   return l;
 }
@@ -366,7 +418,7 @@ void MTPGraph::retrieve_disjoint_paths() {
     if(e->occupied) {
       int l = retrieve_one_path(e, 0);
       paths[p] = new Path(l);
-      retrieve_one_path(e, paths[p]->nodes);
+      retrieve_one_path(e, paths[p]);
       p++;
     }
   }