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Diffstat (limited to 'framework/src/onos/utils/misc/src/main/java/org/onlab/graph/KshortestPathSearch.java')
-rw-r--r-- | framework/src/onos/utils/misc/src/main/java/org/onlab/graph/KshortestPathSearch.java | 286 |
1 files changed, 286 insertions, 0 deletions
diff --git a/framework/src/onos/utils/misc/src/main/java/org/onlab/graph/KshortestPathSearch.java b/framework/src/onos/utils/misc/src/main/java/org/onlab/graph/KshortestPathSearch.java new file mode 100644 index 00000000..820e912c --- /dev/null +++ b/framework/src/onos/utils/misc/src/main/java/org/onlab/graph/KshortestPathSearch.java @@ -0,0 +1,286 @@ +/* + * Copyright 2014-2015 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); + } + +} |