X-Git-Url: https://fleuret.org/cgi-bin/gitweb/gitweb.cgi?a=blobdiff_plain;f=mtp_graph.cc;h=4608b82f428fe252c96aec1fbf6656f753f3238b;hb=9dba69873c4b22f885a70740df7f57b0d6a37fd6;hp=a60e532587bca4cb184a855abd629e6cbc8a2023;hpb=6e7fbc025b89997ae663bda0696eca80a6d3f93b;p=mtp.git

diff --git a/mtp_graph.cc b/mtp_graph.cc
index a60e532..4608b82 100644
--- a/mtp_graph.cc
+++ b/mtp_graph.cc
@@ -41,13 +41,13 @@ 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 +55,8 @@ 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;
@@ -68,17 +68,23 @@ 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;
+  }
 }
 
 //////////////////////////////////////////////////////////////////////
@@ -102,7 +108,7 @@ MTPGraph::MTPGraph(int nb_vertices, int nb_edges,
   }
 
   for(int e = 0; e < nb_edges; e++) {
-    _vertices[from[e]].add_edge(_edges + e);
+    _vertices[from[e]].add_leaving_edge(_edges + e);
     _edges[e].occupied = 0;
     _edges[e].id = e;
     _edges[e].origin_vertex = _vertices + from[e];
@@ -163,20 +169,6 @@ void MTPGraph::print_dot(ostream *os) {
 
 //////////////////////////////////////////////////////////////////////
 
-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 +187,7 @@ 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;
       }
@@ -207,8 +199,8 @@ void MTPGraph::force_positivized_lengths() {
 }
 
 // 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) {
+// distance_from_source and pred_edge_toward_source.
+void MTPGraph::find_shortest_path() {
   Vertex **tmp_front;
   int tmp_front_size;
   Vertex *v, *tv;
@@ -217,7 +209,7 @@ void MTPGraph::find_shortest_path(Vertex **_front, Vertex **_new_front) {
 
   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].pred_edge_toward_source = 0;
     _vertices[v].iteration = 0;
   }
 
@@ -238,7 +230,7 @@ void MTPGraph::find_shortest_path(Vertex **_front, Vertex **_new_front) {
         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;
             tv->iteration = iteration;
@@ -270,26 +262,22 @@ void MTPGraph::find_best_paths(scalar_t *lengths) {
 
   // 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();
-
-  // #warning
-  // initialize_positivized_lengths_with_min();
+  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) {
+    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 +286,8 @@ 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 +299,47 @@ 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 +362,7 @@ 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++;
     }
   }