From cdf649aeef318cc5c3dae231d9b1c16352d13515 Mon Sep 17 00:00:00 2001
From: Francois Fleuret <francois@fleuret.org>
Date: Sat, 25 Aug 2012 12:45:13 +0200
Subject: [PATCH] Added some comments.

---
 mtp_graph.cc |  8 ++++----
 mtp_graph.h  |  2 +-
 tracker.cc   | 39 +++++++++++++++++++++++++--------------
 3 files changed, 30 insertions(+), 19 deletions(-)

diff --git a/mtp_graph.cc b/mtp_graph.cc
index 1f0f6d3..49b97f7 100644
--- a/mtp_graph.cc
+++ b/mtp_graph.cc
@@ -96,7 +96,7 @@ void Vertex::del_leaving_edge(Edge *e) {
 //////////////////////////////////////////////////////////////////////
 
 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;
@@ -114,11 +114,11 @@ MTPGraph::MTPGraph(int nb_vertices, int nb_edges,
   }
 
   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;
diff --git a/mtp_graph.h b/mtp_graph.h
index bd805c2..5988688 100644
--- a/mtp_graph.h
+++ b/mtp_graph.h
@@ -60,7 +60,7 @@ public:
   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();
diff --git a/tracker.cc b/tracker.cc
index 0bb1449..362e52d 100644
--- a/tracker.cc
+++ b/tracker.cc
@@ -225,6 +225,8 @@ void Tracker::build_graph() {
     }
   }
 
+  // The edges from the source to the first time frame
+
   for(int l = 0; l < _nb_locations; l++) {
     node_from[e] = source;
     node_to[e] = 1 + l + 0 * _nb_locations;
@@ -232,26 +234,33 @@ void Tracker::build_graph() {
     e++;
   }
 
-  for(int t = 0; t < _nb_time_steps; t++) {
+  // The edges from the last frame to the sink
+
+  for(int l = 0; l < _nb_locations; l++) {
+    node_from[e] = late_pair_node(_nb_time_steps - 1, l);
+    node_to[e] = sink;
+    _edge_lengths[e] = 0.0;
+    e++;
+  }
+
+  // The edges between frames, corresponding to allowed motions
+
+  for(int t = 0; t < _nb_time_steps - 1; t++) {
     for(int l = 0; l < _nb_locations; l++) {
-      if(t == _nb_time_steps - 1) {
-        node_from[e] = late_pair_node(t, l);
-        node_to[e] = sink;
-        _edge_lengths[e] = 0.0;
-        e++;
-      } else {
-        for(int k = 0; k < _nb_locations; k++) {
-          if(allowed_motion[l][k]) {
-            node_from[e] = late_pair_node(t, l);
-            node_to[e] = early_pair_node(t+1, k);
-            _edge_lengths[e] = 0.0;
-            e++;
-          }
+      for(int k = 0; k < _nb_locations; k++) {
+        if(allowed_motion[l][k]) {
+          node_from[e] = late_pair_node(t, l);
+          node_to[e] = early_pair_node(t+1, k);
+          _edge_lengths[e] = 0.0;
+          e++;
         }
       }
     }
   }
 
+  // The edges from the source to the entrances, and from the exits to
+  // the sink
+
   for(int t = 0; t < _nb_time_steps; t++) {
     for(int l = 0; l < _nb_locations; l++) {
       if(t > 0 && entrances[l]) {
@@ -269,6 +278,8 @@ void Tracker::build_graph() {
     }
   }
 
+  // We are done, build the graph
+
   _graph = new MTPGraph(nb_vertices, nb_edges,
                         node_from, node_to,
                         source, sink);
-- 
2.39.5