From 3fe1f714514a55322e22717eeddf76f9f019c658 Mon Sep 17 00:00:00 2001
From: Francois Fleuret <francois@fleuret.org>
Date: Tue, 21 Aug 2012 14:59:49 -0700
Subject: [PATCH] Prevent the same vertex to be added twice to the front in
 find_shortest_path.

---
 mtp.cc | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/mtp.cc b/mtp.cc
index a9388f6..b400650 100644
--- a/mtp.cc
+++ b/mtp.cc
@@ -56,11 +56,9 @@ public:
 
 class Vertex {
 public:
-  int id;
-
+  int id, iteration;
   Edge *root_edge;
   scalar_t distance_from_source;
-
   Vertex *pred_vertex;
   Edge *pred_edge;
 
@@ -89,7 +87,6 @@ class Graph {
   Edge *edge_heap;
   Vertex *vertices;
   Vertex *source, *sink;
-
 public:
   Graph(int nb_vertices, int nb_edges, int *from, int *to, scalar_t *lengths,
         int source, int sink);
@@ -174,7 +171,7 @@ void Graph::find_shortest_path(Vertex **front, Vertex **new_front) {
   for(int n = 0; n < nb_vertices; n++) {
     for(Edge *e = vertices[n].root_edge; e; e = e->next) {
       if(e->work_length < 0) {
-        cerr << "DEBUG error in find_shortest_path: Edge fixed lengths have to be positive."
+        cerr << "DEBUG error in find_shortest_path: Edge work lengths have to be positive."
              << endl;
         abort();
       }
@@ -186,14 +183,18 @@ void Graph::find_shortest_path(Vertex **front, Vertex **new_front) {
     vertices[v].distance_from_source = FLT_MAX;
     vertices[v].pred_vertex = 0;
     vertices[v].pred_edge = 0;
+    vertices[v].iteration = 0;
   }
 
+  int iteration = 0;
+
   int front_size = 0, new_front_size;
   front[front_size++] = source;
   source->distance_from_source = 0;
 
   do {
     new_front_size = 0;
+    iteration++;
     for(int f = 0; f < front_size; f++) {
       v = front[f];
       for(Edge *e = v->root_edge; e; e = e->next) {
@@ -203,7 +204,10 @@ void Graph::find_shortest_path(Vertex **front, Vertex **new_front) {
           tv->distance_from_source = d;
           tv->pred_vertex = v;
           tv->pred_edge = e;
-          new_front[new_front_size++] = tv;
+          if(tv->iteration < iteration) {
+            new_front[new_front_size++] = tv;
+            tv->iteration = iteration;
+          }
         }
       }
     }
-- 
2.20.1