| /* |
| * Copyright 2014 Open Networking Laboratory |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.onlab.graph; |
| |
| import java.util.ArrayList; |
| //import java.util.HashMap; |
| import java.util.Iterator; |
| import java.util.List; |
| //import java.util.Map; |
| //import java.util.PriorityQueue; |
| import java.util.Set; |
| |
| import static org.onlab.graph.GraphPathSearch.ALL_PATHS; |
| |
| /** |
| * K-shortest-path graph search algorithm capable of finding not just one, |
| * but K shortest paths with ascending order between the source and destinations. |
| */ |
| |
| public class KshortestPathSearch<V extends Vertex, E extends Edge<V>> { |
| |
| // Define class variables. |
| private Graph<V, E> immutableGraph; |
| private MutableGraph<V, E> mutableGraph; |
| private List<List<E>> pathResults = new ArrayList<List<E>>(); |
| private List<List<E>> pathCandidates = new ArrayList<List<E>>(); |
| private V source; |
| private V sink; |
| private int numK = 0; |
| private EdgeWeight<V, E> weight = null; |
| // private PriorityQueue<List<E>> pathCandidates = new PriorityQueue<List<E>>(); |
| |
| // Initialize the graph. |
| public KshortestPathSearch(Graph<V, E> graph) { |
| immutableGraph = graph; |
| mutableGraph = new MutableAdjacencyListsGraph<>(graph.getVertexes(), |
| graph.getEdges()); |
| } |
| |
| public List<List<E>> search(V src, |
| V dst, |
| EdgeWeight<V, E> wei, |
| int k) { |
| |
| weight = wei; |
| source = src; |
| sink = dst; |
| numK = k; |
| // pathCandidates = new PriorityQueue<List<E>>(); |
| |
| pathResults.clear(); |
| pathCandidates.clear(); |
| |
| // Double check the parameters |
| checkArguments(immutableGraph, src, dst, numK); |
| |
| // DefaultResult result = new DefaultResult(src, dst); |
| |
| searchKShortestPaths(); |
| |
| return pathResults; |
| } |
| |
| private void checkArguments(Graph<V, E> graph, V src, V dst, int k) { |
| if (graph == null) { |
| throw new NullPointerException("graph is null"); |
| } |
| if (!graph.getVertexes().contains(src)) { |
| throw new NullPointerException("source node does not exist"); |
| } |
| if (!graph.getVertexes().contains(dst)) { |
| throw new NullPointerException("target node does not exist"); |
| } |
| if (k <= 0) { |
| throw new NullPointerException("K is negative or 0"); |
| } |
| if (weight == null) { |
| throw new NullPointerException("the cost matrix is null"); |
| } |
| } |
| |
| private void searchKShortestPaths() { |
| // Step 1: find the shortest path. |
| List<E> shortestPath = searchShortestPath(immutableGraph, source, sink); |
| // no path exists, exit. |
| if (shortestPath == null) { |
| return; |
| } |
| |
| // Step 2: update the results. |
| pathResults.add(shortestPath); |
| // pathCandidates.add(shortestPath); |
| |
| // Step 3: find the other K-1 paths. |
| while (/*pathCandidates.size() > 0 &&*/pathResults.size() < numK) { |
| // 3.1 the spur node ranges from the first node to the last node in the previous k-shortest path. |
| List<E> lastPath = pathResults.get(pathResults.size() - 1); |
| for (int i = 0; i < lastPath.size(); i++) { |
| // 3.1.1 convert the graph into mutable. |
| convertGraph(); |
| // 3.1.2 transform the graph. |
| List<E> rootPath = createSpurNode(lastPath, i); |
| transformGraph(rootPath); |
| // 3.1.3 find the deviation node. |
| V devNode; |
| devNode = getDevNode(rootPath); |
| List<E> spurPath; |
| // 3.1.4 find the shortest path in the transformed graph. |
| spurPath = searchShortestPath(mutableGraph, devNode, sink); |
| // 3.1.5 update the path candidates. |
| if (spurPath != null) { |
| // totalPath = rootPath + spurPath; |
| rootPath.addAll(spurPath); |
| pathCandidates.add(rootPath); |
| } |
| } |
| // 3.2 if there is no spur path, exit. |
| if (pathCandidates.size() == 0) { |
| break; |
| } |
| // 3.3 add the path into the results. |
| addPathResult(); |
| } |
| } |
| |
| @SuppressWarnings({ "rawtypes", "unchecked" }) |
| private List<E> searchShortestPath(Graph<V, E> graph, V src, V dst) { |
| // Determine the shortest path from the source to the destination by using the Dijkstra algorithm. |
| DijkstraGraphSearch dijkstraAlg = new DijkstraGraphSearch(); |
| Set<Path> paths = dijkstraAlg.search(graph, src, dst, weight, ALL_PATHS).paths(); |
| Iterator<Path> itr = paths.iterator(); |
| if (!itr.hasNext()) { |
| return null; |
| } |
| // return the first shortest path only. |
| return (List<E>) itr.next().edges(); |
| } |
| |
| private void convertGraph() { |
| // clear the mutableGraph first |
| if (mutableGraph != null) { |
| ((MutableAdjacencyListsGraph) mutableGraph).clear(); |
| } |
| |
| // create a immutableGraph |
| Set<E> copyEa = immutableGraph.getEdges(); |
| Set<V> copyVa = immutableGraph.getVertexes(); |
| for (V vertex : copyVa) { |
| mutableGraph.addVertex(vertex); |
| } |
| for (E edge : copyEa) { |
| mutableGraph.addEdge(edge); |
| } |
| } |
| |
| private V getDevNode(List<E> path) { |
| V srcA; |
| V dstB; |
| |
| if (path.size() == 0) { |
| return source; |
| } |
| |
| E temp1 = path.get(path.size() - 1); |
| srcA = temp1.src(); |
| dstB = temp1.dst(); |
| |
| if (path.size() == 1) { |
| if (srcA.equals(source)) { |
| return dstB; |
| } else { |
| return srcA; |
| } |
| } else { |
| E temp2 = path.get(path.size() - 2); |
| if (srcA.equals(temp2.src()) || srcA.equals(temp2.dst())) { |
| return dstB; |
| } else { |
| return srcA; |
| } |
| } |
| } |
| |
| private List<E> createSpurNode(List<E> path, int n) { |
| List<E> root = new ArrayList<E>(); |
| |
| for (int i = 0; i < n; i++) { |
| root.add(path.get(i)); |
| } |
| return root; |
| } |
| |
| private void transformGraph(List<E> rootPath) { |
| List<E> prePath; |
| //remove edges |
| for (int i = 0; i < pathResults.size(); i++) { |
| prePath = pathResults.get(i); |
| if (prePath.size() == 1) { |
| mutableGraph.removeEdge(prePath.get(0)); |
| } else if (comparePath(rootPath, prePath)) { |
| for (int j = 0; j <= rootPath.size(); j++) { |
| mutableGraph.removeEdge(prePath.get(j)); |
| } |
| } |
| } |
| for (int i = 0; i < pathCandidates.size(); i++) { |
| prePath = pathCandidates.get(i); |
| if (prePath.size() == 1) { |
| mutableGraph.removeEdge(prePath.get(0)); |
| } else if (comparePath(rootPath, prePath)) { |
| for (int j = 0; j <= rootPath.size(); j++) { |
| mutableGraph.removeEdge(prePath.get(j)); |
| } |
| } |
| } |
| |
| if (rootPath.size() == 0) { |
| return; |
| } |
| |
| //remove nodes |
| List<V> nodes = new ArrayList<V>(); |
| nodes.add(source); |
| V pre = source; |
| V srcA; |
| V dstB; |
| for (int i = 0; i < rootPath.size() - 1; i++) { |
| E temp = rootPath.get(i); |
| srcA = temp.src(); |
| dstB = temp.dst(); |
| |
| if (srcA.equals(pre)) { |
| nodes.add(dstB); |
| pre = dstB; |
| } else { |
| nodes.add(srcA); |
| pre = srcA; |
| } |
| } |
| for (int i = 0; i < nodes.size(); i++) { |
| mutableGraph.removeVertex(nodes.get(i)); |
| } |
| } |
| |
| private boolean comparePath(List<E> path1, List<E> path2) { |
| if (path1.size() > path2.size()) { |
| return false; |
| } |
| if (path1.size() == 0) { |
| return true; |
| } |
| for (int i = 0; i < path1.size(); i++) { |
| if (path1.get(i) != path2.get(i)) { |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| private void addPathResult() { |
| List<E> sp; |
| sp = pathCandidates.get(0); |
| for (int i = 1; i < pathCandidates.size(); i++) { |
| if (sp.size() > pathCandidates.get(i).size()) { |
| sp = pathCandidates.get(i); |
| } |
| } |
| pathResults.add(sp); |
| // Log.info(sp.toString()); |
| pathCandidates.remove(sp); |
| } |
| |
| } |