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feat(dijkstra): mark labels as reached to increase performance

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This commit is contained in:
Paul Alnet 2024-05-03 13:24:05 +02:00
parent dcc2bc0746
commit 6baec1d7dd
2 changed files with 14 additions and 13 deletions
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23
be-graphes-algos/src/main/java/org/insa/graphs/algorithm/shortestpath/DijkstraAlgorithm.java
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@ -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());
}
}
}

4
be-graphes-algos/src/main/java/org/insa/graphs/algorithm/shortestpath/Label.java
View file

@ -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; }