X-Git-Url: https://fleuret.org/cgi-bin/gitweb/gitweb.cgi?p=mtp.git;a=blobdiff_plain;f=mtp_graph.h;h=64308b9c000d6e45de0372080fb504ea39880436;hp=ddf71622bec878921029f66509c60fb0261e1925;hb=HEAD;hpb=fda29b3422f4850d77e4b8f4916251509789d3ac

diff --git a/mtp_graph.h b/mtp_graph.h
index ddf7162..64308b9 100644
--- a/mtp_graph.h
+++ b/mtp_graph.h
@@ -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/>.
+ *
+ */
 
 #ifndef MTP_GRAPH_H
 #define MTP_GRAPH_H
@@ -24,26 +30,38 @@
 using namespace std;
 
 #include "misc.h"
+#include "path.h"
 
 class Vertex;
 class Edge;
 
-class Path {
-public:
-  Path(int l);
-  ~Path();
-  int length;
-  int *nodes;
-};
-
 class MTPGraph {
-  void initialize_positivized_lengths_with_min();
+
+  // Uses the estimated vertex distances to the source to make all the
+  // edge lengths positive, resulting in an identical added value to
+  // all the paths from the same initial node to the same final node
+  // (in particular from source to sink)
   void update_positivized_lengths();
+
+  // It may happen that numerical errors in update_positivized_lengths
+  // make the resulting lengths negative, albeit very small. The
+  // following method forces all negative lengths to zero, and prints
+  // the total correction when compiled in VERBOSE mode.
   void force_positivized_lengths();
-  void find_shortest_path(Vertex **front, Vertex **new_front);
-  int retrieve_one_path(Edge *e, int *nodes);
 
-  Vertex **_front, **_new_front;
+  // Visit the vertices according to _dp_order and update their
+  // distance from the source
+  void dp_compute_distances();
+
+  // Set in every vertex pred_edge_toward_source correspondingly to
+  // the path of shortest length. The current implementation is
+  // Dijkstra with a Binary Heap (and not with Fibonnaci heap (yet))
+  void find_shortest_path();
+
+  // Follows the path starting on edge e and returns the number of
+  // nodes to reach the sink. If path is non-null, stores in it the
+  // nodes met along the path, and computes path->length properly.
+  int retrieve_one_path(Edge *e, Path *path, int *used_edges);
 
   int _nb_vertices, _nb_edges;
   Vertex *_source, *_sink;
@@ -51,17 +69,35 @@ class MTPGraph {
   Edge *_edges;
   Vertex *_vertices;
 
+  // For Dijkstra
+  Vertex **_heap;
+
+  // Updating the distances from the source in that order will work in
+  // the original graph (which has to be a DAG)
+  Vertex **_dp_order;
+
+  // Fills _dp_order
+  void compute_dp_ordering();
 public:
 
+  // These variables are filled when retrieve_disjoint_paths is called
   int nb_paths;
   Path **paths;
 
-  MTPGraph(int nb_vertices, int nb_edges, int *from, int *to,
+  MTPGraph(int nb_vertices, int nb_edges, int *vertex_from, int *vertex_to,
            int source, int sink);
 
   ~MTPGraph();
 
+  // Compute the family of paths with minimum total length, set the
+  // edge occupied fields accordingly.
   void find_best_paths(scalar_t *lengths);
+
+  // Retrieve the paths corresponding to the occupied edges, and save
+  // the result in the nb_paths and paths fields. If the paths are not
+  // node-disjoint, there are multiple families of paths that
+  // "explain" the edge occupancies, and this method picks one of them
+  // arbitrarily.
   void retrieve_disjoint_paths();
 
   void print(ostream *os);