Added README.md

[mtp.git] / mtp_graph.h

diff --git a/mtp_graph.h b/mtp_graph.h
index b07e461..64308b9 100644 (file)
--- a/mtp_graph.h
+++ b/mtp_graph.h
@@ -26,7 +26,6 @@
 #define MTP_GRAPH_H
 
 #include <iostream>
-#include <cmath>
 
 using namespace std;
 
@@ -37,22 +36,32 @@ class Vertex;
 class Edge;
 
 class MTPGraph {
+
+  // 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 force such length to zero, and print the
-  // correction when compiled in VERBOSE mode.
+  // following method forces all negative lengths to zero, and prints
+  // the total correction when compiled in VERBOSE mode.
   void force_positivized_lengths();
-  // Set the edge pred_edge_toward_source correspondingly to the path
-  // of shortest length. The current implementation is not Dijkstra's!
+
+  // 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 its length. If
-  // nodes is non-null, stores in it the nodes met along the path.
-  int retrieve_one_path(Edge *e, Path *path);
-  // Returns if the graph is a DAG
-  int is_dag();
 
-  Vertex **_front, **_new_front;
+  // 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;
@@ -60,6 +69,15 @@ 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
@@ -71,7 +89,15 @@ public:
 
   ~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);