| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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.apache.drill.common.graph; |
| |
| import java.util.Collection; |
| import java.util.Iterator; |
| import java.util.LinkedList; |
| import java.util.List; |
| |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| public class GraphAlgos { |
| static final Logger logger = LoggerFactory.getLogger(GraphAlgos.class); |
| |
| public static class TopoSorter<V extends GraphValue<V>> { |
| final List<AdjacencyList<V>.Node> sorted = new LinkedList<AdjacencyList<V>.Node>(); |
| final AdjacencyList<V> rGraph; |
| |
| private TopoSorter(AdjacencyList<V> graph, boolean reverse) { |
| graph.clearVisited(); |
| |
| if (reverse) { |
| this.rGraph = graph.getReversedList(); |
| } else { |
| this.rGraph = graph; |
| } |
| Collection<AdjacencyList<V>.Node> sourceNodes = rGraph.getInternalRootNodes(); |
| |
| for (AdjacencyList<V>.Node n : sourceNodes) { |
| visit(n); |
| } |
| } |
| |
| private void visit(AdjacencyList<V>.Node n) { |
| if (n.visited) { |
| return; |
| } |
| |
| n.visited = true; |
| List<Edge<AdjacencyList<V>.Node>> edges = rGraph.getAdjacent(n); |
| if (edges != null) { |
| for (Edge<AdjacencyList<V>.Node> e : edges) { |
| visit(e.to); |
| } |
| } |
| |
| sorted.add(n); |
| |
| } |
| |
| /** |
| * Execute a depth-first sort on the reversed DAG. |
| * |
| * @param graph the adjacency list for the DAG. |
| * @param reverse true if reversed, otherwise false |
| * |
| * @return |
| */ |
| static <V extends GraphValue<V>> List<AdjacencyList<V>.Node> sortInternal(AdjacencyList<V> graph, boolean reverse) { |
| TopoSorter<V> ts = new TopoSorter<V>(graph, reverse); |
| return ts.sorted; |
| } |
| |
| public static <V extends GraphValue<V>> List<V> sort(Graph<V, ?, ?> graph) { |
| AdjacencyList<V> l = graph.getAdjList(); |
| return l.convert(sortInternal(l, true)); |
| } |
| |
| public static <V extends GraphValue<V>> List<V> sortLogical(Graph<V, ?, ?> graph) { |
| AdjacencyList<V> l = graph.getAdjList(); |
| return l.convert(sortInternal(l, false)); |
| } |
| } |
| |
| static <V extends GraphValue<V>> List<List<AdjacencyList<V>.Node>> checkDirected(AdjacencyList<V> graph) { |
| Tarjan<V> t = new Tarjan<V>(); |
| List<List<AdjacencyList<V>.Node>> subgraphs = t.executeTarjan(graph); |
| for (Iterator<List<AdjacencyList<V>.Node>> i = subgraphs.iterator(); i.hasNext();) { |
| List<AdjacencyList<V>.Node> l = i.next(); |
| if (l.size() == 1) { |
| i.remove(); |
| } |
| } |
| return subgraphs; |
| } |
| |
| public static <V extends GraphValue<V>> List<List<AdjacencyList<V>.Node>> checkDirected(Graph<V, ?, ?> graph) { |
| return checkDirected(graph.getAdjList()); |
| } |
| |
| public static class Tarjan<V extends GraphValue<V>> { |
| |
| private int index = 0; |
| private List<AdjacencyList<V>.Node> stack = new LinkedList<AdjacencyList<V>.Node>(); |
| private List<List<AdjacencyList<V>.Node>> SCC = new LinkedList<List<AdjacencyList<V>.Node>>(); |
| |
| public List<List<AdjacencyList<V>.Node>> executeTarjan(AdjacencyList<V> graph) { |
| SCC.clear(); |
| index = 0; |
| stack.clear(); |
| if (graph != null) { |
| List<AdjacencyList<V>.Node> nodeList = new LinkedList<AdjacencyList<V>.Node>(graph.getNodeSet()); |
| for (AdjacencyList<V>.Node node : nodeList) { |
| if (node.index == -1) { |
| tarjan(node, graph); |
| } |
| } |
| } |
| return SCC; |
| } |
| |
| private List<List<AdjacencyList<V>.Node>> tarjan(AdjacencyList<V>.Node v, AdjacencyList<V> list) { |
| v.index = index; |
| v.lowlink = index; |
| index++; |
| stack.add(0, v); |
| List<Edge<AdjacencyList<V>.Node>> l = list.getAdjacent(v); |
| if (l != null) { |
| for (Edge<AdjacencyList<V>.Node> e : l) { |
| AdjacencyList<V>.Node n = e.to; |
| if (n.index == -1) { |
| tarjan(n, list); |
| v.lowlink = Math.min(v.lowlink, n.lowlink); |
| } else if (stack.contains(n)) { |
| v.lowlink = Math.min(v.lowlink, n.index); |
| } |
| } |
| } |
| if (v.lowlink == v.index) { |
| AdjacencyList<V>.Node n; |
| List<AdjacencyList<V>.Node> component = new LinkedList<AdjacencyList<V>.Node>(); |
| do { |
| n = stack.remove(0); |
| component.add(n); |
| } while (n != v); |
| SCC.add(component); |
| } |
| return SCC; |
| } |
| } |
| |
| } |