From: Francois Fleuret <francois@fleuret.org>
Date: Wed, 19 Dec 2012 17:58:25 +0000 (+0100)
Subject: Cosmetics.
X-Git-Url: https://fleuret.org/cgi-bin/gitweb/gitweb.cgi?a=commitdiff_plain;h=14e3b33cbe1e0d7deb0b4aa697f6c8b5d43e2963;p=mtp.git

Cosmetics.
---

diff --git a/mtp_graph.cc b/mtp_graph.cc
index 9bce055..aa294b4 100644
--- a/mtp_graph.cc
+++ b/mtp_graph.cc
@@ -46,11 +46,7 @@ public:
   Edge *leaving_edges;
   scalar_t distance_from_source;
   Edge *pred_edge_toward_source;
-
-  int last_change; // Used to mark which edges have already been
-                   // processed in some methods
-
-  Vertex **heap_position;
+  Vertex **heap_slot;
 
   Vertex();
 
@@ -98,7 +94,12 @@ void Vertex::del_leaving_edge(Edge *e) {
 //////////////////////////////////////////////////////////////////////
 
 static int compare_vertex(const void *v1, const void *v2) {
-  return (*((Vertex **) v1))->last_change - (*((Vertex **) v2))->last_change;
+  scalar_t delta =
+    (*((Vertex **) v1))->distance_from_source -
+    (*((Vertex **) v2))->distance_from_source;
+  if(delta < 0) return -1;
+  else if(delta > 0) return 1;
+  else return 0;
 }
 
 MTPGraph::MTPGraph(int nb_vertices, int nb_edges,
@@ -124,16 +125,16 @@ MTPGraph::MTPGraph(int nb_vertices, int nb_edges,
 
   for(int v = 0; v < _nb_vertices; v++) {
     _heap[v] = &_vertices[v];
-    _vertices[v].heap_position = &_heap[v];
+    _vertices[v].heap_slot = &_heap[v];
   }
 
   paths = 0;
   nb_paths = 0;
 
-  if(check_DAG_and_set_last_change()) {
-    // Here the last_change field of every vertex tells us how many
-    // iterations of DP we need to reach it. Hence we only have to
-    // process the vertex in that order.
+  if(compute_dp_distances()) {
+    // Here the distance_from_source field of every vertex is the
+    // number of DP iterations needed to update it. Hence we only have
+    // to process the vertex in that order.
     for(int v = 0; v < _nb_vertices; v++) { _dp_order[v] = &_vertices[v]; }
     qsort(_dp_order, _nb_vertices, sizeof(Vertex *), compare_vertex);
   } else {
@@ -211,17 +212,8 @@ void MTPGraph::force_positivized_lengths() {
     if(e->positivized_length < 0) {
 
 #ifdef VERBOSE
-      if((e->origin_vertex->last_change < 0 && e->terminal_vertex->last_change >= 0) ||
-         (e->origin_vertex->last_change >= 0 && e->terminal_vertex->last_change < 0)) {
-        cout << "Inconsistent non-connexity (this should never happen)." << endl;
-        abort();
-      }
-      if(e->origin_vertex->last_change >= 0 &&
-         e->terminal_vertex->last_change >= 0 &&
-         e->positivized_length < 0) {
-        residual_error -= e->positivized_length;
-        max_error = max(max_error, - e->positivized_length);
-      }
+      residual_error -= e->positivized_length;
+      max_error = max(max_error, - e->positivized_length);
 #endif
       e->positivized_length = 0.0;
     }
@@ -231,7 +223,7 @@ void MTPGraph::force_positivized_lengths() {
 #endif
 }
 
-int MTPGraph::check_DAG_and_set_last_change() {
+int MTPGraph::compute_dp_distances() {
   Vertex *v;
   Edge *e;
 
@@ -239,7 +231,7 @@ int MTPGraph::check_DAG_and_set_last_change() {
 
   // We put everybody in the active
   for(int k = 0; k < _nb_vertices; k++) {
-    _vertices[k].last_change = 0;
+    _vertices[k].distance_from_source = 0;
     active[k] = &_vertices[k];
   }
 
@@ -247,12 +239,12 @@ int MTPGraph::check_DAG_and_set_last_change() {
   int nb_active = _nb_vertices, pred_nb_active;
 
   do {
-    // We set the last_change field of all the vertices with incoming
+    // We set the distance_from_source field of all the vertices with incoming
     // edges to the current iteration value
     for(int f = 0; f < nb_active; f++) {
       v = active[f];
       for(e = v->leaving_edges; e; e = e->next_leaving_edge) {
-        e->terminal_vertex->last_change = iteration;
+        e->terminal_vertex->distance_from_source = iteration;
       }
     }
 
@@ -262,7 +254,7 @@ int MTPGraph::check_DAG_and_set_last_change() {
     // We keep all the vertices with incoming nodes
     for(int f = 0; f < pred_nb_active; f++) {
       v = active[f];
-      if(v->last_change == iteration) {
+      if(v->distance_from_source == iteration) {
         active[nb_active++] = v;
       }
     }
@@ -278,12 +270,12 @@ int MTPGraph::check_DAG_and_set_last_change() {
 void MTPGraph::decrease_distance_in_heap(Vertex *v) {
   Vertex **p, **h;
   // There is some beauty in that
-  h = v->heap_position;
+  h = v->heap_slot;
   while(h > _heap &&
         (p = _heap + (h - _heap + 1) / 2 - 1,
          (*p)->distance_from_source > (*h)->distance_from_source)) {
     swap(*p, *h);
-    swap((*p)->heap_position, (*h)->heap_position);
+    swap((*p)->heap_slot, (*h)->heap_slot);
     h = p;
   }
 }
@@ -291,23 +283,20 @@ void MTPGraph::decrease_distance_in_heap(Vertex *v) {
 void MTPGraph::increase_distance_in_heap(Vertex *v) {
   Vertex **c1, **c2, **h;
   // There is some beauty in that
-  h = v->heap_position;
+  h = v->heap_slot;
   while(c1 = _heap + 2 * (h - _heap + 1) - 1, c2 = c1 + 1,
-        (c1 < _heap + _heap_size &&
-         (*c1)->distance_from_source < (*h)->distance_from_source)
+        (c1 < _heap + _heap_size && (*c1)->distance_from_source < (*h)->distance_from_source)
         ||
-        (c2 < _heap + _heap_size &&
-          (*c2)->distance_from_source < (*h)->distance_from_source)
+        (c2 < _heap + _heap_size && (*c2)->distance_from_source < (*h)->distance_from_source)
         ) {
     if(c1 < _heap + _heap_size &&
-       !(c2 < _heap + _heap_size &&
-         (*c2)->distance_from_source < (*c1)->distance_from_source)){
+     !(c2 < _heap + _heap_size && (*c2)->distance_from_source < (*c1)->distance_from_source)){
       swap(*c1, *h);
-      swap((*c1)->heap_position, (*h)->heap_position);
+      swap((*c1)->heap_slot, (*h)->heap_slot);
       h = c1;
     } else {
       swap(*c2, *h);
-      swap((*c2)->heap_position, (*h)->heap_position);
+      swap((*c2)->heap_slot, (*h)->heap_slot);
       h = c2;
     }
   }
@@ -366,7 +355,7 @@ void MTPGraph::find_shortest_path() {
     _heap_size--;
     a = _heap;
     b = _heap + _heap_size;
-    swap(*a, *b); swap((*a)->heap_position, (*b)->heap_position);
+    swap(*a, *b); swap((*a)->heap_slot, (*b)->heap_slot);
     increase_distance_in_heap(_heap[0]);
 
     // Now update the neighbors of the currently closest to the source
@@ -374,7 +363,7 @@ void MTPGraph::find_shortest_path() {
       d = v->distance_from_source + e->positivized_length;
       tv = e->terminal_vertex;
       if(d < tv->distance_from_source) {
-        ASSERT(tv->heap_position - _heap < _heap_size);
+        ASSERT(tv->heap_slot - _heap < _heap_size);
         tv->distance_from_source = d;
         tv->pred_edge_toward_source = e;
         decrease_distance_in_heap(tv);
diff --git a/mtp_graph.h b/mtp_graph.h
index bad0df5..c910520 100644
--- a/mtp_graph.h
+++ b/mtp_graph.h
@@ -66,10 +66,9 @@ class MTPGraph {
   // nodes met along the path, and computes path->length properly.
   int retrieve_one_path(Edge *e, Path *path);
 
-  // Returns if the graph is a DAG, and set the last_change field of
-  // each vertex to the maximum number of iterations required to reach
-  // it
-  int check_DAG_and_set_last_change();
+  // Set the distance_from_source fields to the number of DP
+  // iterations needed to update it. Abort if the graph is not a DAG.
+  int compute_dp_distances();
 
   int _nb_vertices, _nb_edges;
   Vertex *_source, *_sink;