2 * Copyright (c) 2016 Orange. All rights reserved.
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6 * and is available at http://www.eclipse.org/legal/epl-v10.html
8 package org.opendaylight.algo.impl;
10 import java.util.HashMap;
11 import java.util.List;
12 import org.opendaylight.graph.ConnectedEdge;
13 import org.opendaylight.graph.ConnectedGraph;
14 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.graph.rev191125.graph.topology.graph.VertexKey;
15 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.path.computation.rev200120.ComputationStatus;
16 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.path.computation.rev200120.ConstrainedPath;
17 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.path.computation.rev200120.ConstrainedPathBuilder;
18 import org.opendaylight.yang.gen.v1.urn.opendaylight.params.xml.ns.yang.path.computation.rev200120.PathConstraints;
19 import org.opendaylight.yangtools.yang.common.Uint32;
20 import org.slf4j.Logger;
21 import org.slf4j.LoggerFactory;
24 * This Class implements a simple Shortest Path First path computation algorithm based on standard IGP Metric.
26 * @author Olivier Dugeon
27 * @author Philippe Niger
28 * @author Philippe Cadro
30 public class ShortestPathFirst extends AbstractPathComputation {
32 private static final Logger LOG = LoggerFactory.getLogger(ShortestPathFirst.class);
34 private HashMap<Long, CspfPath> visitedVertices;
36 public ShortestPathFirst(ConnectedGraph graph) {
38 visitedVertices = new HashMap<Long, CspfPath>();
41 public ConstrainedPath computeP2pPath(VertexKey src, VertexKey dst, PathConstraints cts) {
42 ConstrainedPathBuilder cpathBuilder;
43 List<ConnectedEdge> edges;
45 int currentCost = Integer.MAX_VALUE;
47 LOG.info("Start SPF Path Computation from {} to {} with constraints {}", src, dst, cts);
49 /* Initialize algorithm */
50 this.constraints = cts;
51 cpathBuilder = initializePathComputation(src, dst);
52 if (cpathBuilder.getStatus() == ComputationStatus.Failed) {
53 LOG.warn("Initial configurations are not met. Abort!");
54 return cpathBuilder.build();
57 visitedVertices.clear();
59 while (priorityQueue.size() != 0) {
60 currentPath = priorityQueue.poll();
61 visitedVertices.put(currentPath.getVertexKey(), currentPath);
62 LOG.debug("Process path to Vertex {} from Priority Queue", currentPath.getVertex().toString());
63 edges = currentPath.getVertex().getOutputConnectedEdges();
65 for (ConnectedEdge edge : edges) {
66 /* Check that Edge point to a valid Vertex and is suitable for the Constraint Address Family */
67 if (pruneEdge(edge, currentPath)) {
68 LOG.trace(" Prune Edge {}", edge.toString());
71 if ((relax(edge, currentPath)) && (pathDestination.getCost() < currentCost)) {
72 currentCost = pathDestination.getCost();
73 cpathBuilder.setPathDescription(getPathDescription(pathDestination.getPath()))
74 .setMetric(Uint32.valueOf(pathDestination.getCost()))
75 .setStatus(ComputationStatus.Active);
76 LOG.debug(" Found a valid path up to destination {}", cpathBuilder.getPathDescription());
80 /* The priority queue is empty => all the possible (vertex, path) elements have been explored
81 * The "ConstrainedPathBuilder" object contains the optimal path if it exists
82 * Otherwise an empty path with status failed is returned
84 if ((cpathBuilder.getStatus() == ComputationStatus.InProgress)
85 || (cpathBuilder.getPathDescription().size() == 0)) {
86 cpathBuilder.setStatus(ComputationStatus.Failed);
88 cpathBuilder.setStatus(ComputationStatus.Completed);
90 return cpathBuilder.build();
93 private boolean relax(ConnectedEdge edge, CspfPath currentPath) {
94 LOG.debug(" Start relaxing Edge {} to Vertex {}", edge.toString(), edge.getDestination().toString());
95 final Long nextVertexKey = edge.getDestination().getKey();
97 /* Verify if we have not visited this Vertex to avoid loop */
98 if (visitedVertices.containsKey(nextVertexKey)) {
102 /* Get Next Vertex from processedPath or create a new one if it has not yet processed */
103 CspfPath nextPath = processedPath.get(nextVertexKey);
104 if (nextPath == null) {
105 nextPath = new CspfPath(edge.getDestination());
106 processedPath.put(nextPath.getVertexKey(), nextPath);
109 /* Compute Cost from source to this next Vertex and add or update it in the Priority Queue
110 * if total path Cost is lower than cost associated to this next Vertex.
111 * This could occurs if we process a Vertex that as not yet been visited in the Graph
112 * or if we found a shortest path up to this Vertex. */
113 int totalCost = edge.getEdge().getEdgeAttributes().getMetric().intValue() + currentPath.getCost();
114 if (nextPath.getCost() > totalCost) {
115 nextPath.setCost(totalCost)
116 .replacePath(currentPath.getPath())
117 .addConnectedEdge(edge);
118 /* It is not possible to directly update the CspfPath in the Priority Queue. Indeed, if we modify the path
119 * weight, the Priority Queue must be re-ordered. So, we need fist to remove the CspfPath if it is present
120 * in the Priority Queue, then, update the Path Weight, and finally (re-)insert it in the Priority Queue.
122 priorityQueue.removeIf((path) -> path.getVertexKey().equals(nextVertexKey));
123 nextPath.setKey(totalCost);
124 priorityQueue.add(nextPath);
125 LOG.debug(" Added path to Vertex {} in the Priority Queue with weight {}",
126 nextPath.getVertex().toString(), nextPath.getKey());
128 /* Return True if we reach the destination, false otherwise */
129 return pathDestination.equals(nextPath);