Added some comments.

[mtp.git] / tracker.cc

diff --git a/tracker.cc b/tracker.cc
index 0bb1449..362e52d 100644 (file)
--- 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);