From 6baec1d7dd53a51e96fccee4d60f05cb279a562a Mon Sep 17 00:00:00 2001
From: Paul ALNET <alnet@insa-toulouse.fr>
Date: Fri, 3 May 2024 13:24:05 +0200
Subject: [PATCH] feat(dijkstra): mark labels as reached to increase
 performance

---
 .../shortestpath/DijkstraAlgorithm.java       | 23 ++++++++-----------
 .../graphs/algorithm/shortestpath/Label.java  |  4 ++++
 2 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/be-graphes-algos/src/main/java/org/insa/graphs/algorithm/shortestpath/DijkstraAlgorithm.java b/be-graphes-algos/src/main/java/org/insa/graphs/algorithm/shortestpath/DijkstraAlgorithm.java
index c0af685..7c7c148 100644
--- a/be-graphes-algos/src/main/java/org/insa/graphs/algorithm/shortestpath/DijkstraAlgorithm.java
+++ b/be-graphes-algos/src/main/java/org/insa/graphs/algorithm/shortestpath/DijkstraAlgorithm.java
@@ -51,7 +51,7 @@ public class DijkstraAlgorithm extends ShortestPathAlgorithm {
         // On considère le sommet x à chaque itération
         Label x = s;
 
-        int dest_id = data.getDestination().getId();
+        final int dest_id = data.getDestination().getId();
         while (!tas.isEmpty() && !(labels.get(dest_id).getNode().equals(x.getNode()))) {
             x = tas.deleteMin();
             x.mark();
@@ -63,29 +63,26 @@ public class DijkstraAlgorithm extends ShortestPathAlgorithm {
                 Label successor = labels.get(successorArc.getDestination().getId());
 
                 if (!successor.isMarked() && data.isAllowed(successorArc)) {
-                    // This loop serves to get the lentgh of the arc as
+                    // This loop serves to get the length of the arc as
                     // we know its origin and destination
                     for (Arc arc : x.getNode().getSuccessors()) {
-                        if (successor.getNode() == arc.getDestination()) {
+                        if (successor.getNode().equals(arc.getDestination())) {
                             arc_cost = arc.getLength();
                         }
                     }
-                    float possible_path_cost = x.getCost() + arc_cost;
+                    final float possible_path_cost = x.getCost() + arc_cost;
                     if (successor.getCost() > possible_path_cost) {
                         // Mise à jour du label
                         successor.setPathCost(possible_path_cost);
                         successor.setParentNode(x.getNode());
-                        // Si y est déjà dans le tas, on va l'update, pas l'insérer
-                        // On a pas de fonction update donc on fait un remove puis insert
-                        if (tas.array.contains(successor)) {
-                            tas.remove(successor);
+                        // Si le noeud n'a pas déjà était rajouté au tas, on le rajoute
+                        // isReached permet de vérifier en complexité O(1)
+                        // C'est un léger coût en mémoire pour un gain en vitesse
+                        if (!successor.isReached()) {
                             tas.insert(successor);
+                            successor.markReached();
+                            notifyNodeReached(successor.getNode());
                         }
-                        // il n'y est pas déjà on l'insère
-                        else {
-                            tas.insert(successor);
-                        }
-                        notifyDestinationReached(successor.getNode());
                     }
                 }
             }
diff --git a/be-graphes-algos/src/main/java/org/insa/graphs/algorithm/shortestpath/Label.java b/be-graphes-algos/src/main/java/org/insa/graphs/algorithm/shortestpath/Label.java
index 61c7993..8925660 100644
--- a/be-graphes-algos/src/main/java/org/insa/graphs/algorithm/shortestpath/Label.java
+++ b/be-graphes-algos/src/main/java/org/insa/graphs/algorithm/shortestpath/Label.java
@@ -5,6 +5,7 @@ import org.insa.graphs.model.Node;
 public class Label implements Comparable<Label> {
   Node node;
   boolean marked;
+  boolean reached;
   float pathCost;
   Node parentNode;
 
@@ -12,6 +13,7 @@ public class Label implements Comparable<Label> {
   public Label(Node node) {
     this.node = node;
     this.marked = false;
+    this.marked = false;
     this.pathCost = Float.MAX_VALUE;
     this.parentNode = null;
   }
@@ -19,6 +21,8 @@ public class Label implements Comparable<Label> {
   public Node getNode() { return this.node; }
   public boolean isMarked() { return this.marked; }
   public void mark() { this.marked = true; }
+  public boolean isReached() { return this.reached; }
+  public void markReached() { this.reached = true; }
   public float getPathCost() { return this.pathCost; }
   public void setPathCost(float newCost) { this.pathCost = newCost; }
   public Node getParentNode() { return this.parentNode; }