| /* |
| * Copyright (c) 2015, 2015, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| package org.graalvm.compiler.graph; |
| |
| /** |
| * Union-find data structure for {@link Node Nodes}. |
| * |
| * All operations have an accumulated worst-case complexity of O(a(n)), where a(n) is the inverse of |
| * the Ackermann function A(n,n). |
| */ |
| public class NodeUnionFind extends NodeIdAccessor { |
| |
| private int[] rank; |
| private int[] parent; |
| |
| /** |
| * Create a new union-find data structure for a {@link Graph}. Initially, all nodes are in their |
| * own equivalence set. |
| */ |
| public NodeUnionFind(Graph graph) { |
| super(graph); |
| rank = new int[graph.nodeIdCount()]; |
| parent = new int[graph.nodeIdCount()]; |
| for (int i = 0; i < parent.length; i++) { |
| parent[i] = i; |
| } |
| } |
| |
| /** |
| * Merge the equivalence sets of two nodes. |
| * |
| * After calling this function, find(a) == find(b). |
| */ |
| public void union(Node a, Node b) { |
| union(getNodeId(a), getNodeId(b)); |
| } |
| |
| /** |
| * Get a representative element of the equivalence set of a node. |
| * |
| * This function returns the same representative element for all members of the same equivalence |
| * set, i.e., find(a) == find(b) if and only if a and b are in the same set. |
| */ |
| public Node find(Node a) { |
| int id = find(getNodeId(a)); |
| return graph.getNode(id); |
| } |
| |
| public boolean equiv(Node a, Node b) { |
| return find(getNodeId(a)) == find(getNodeId(b)); |
| } |
| |
| private void union(int a, int b) { |
| int aRoot = find(a); |
| int bRoot = find(b); |
| if (aRoot != bRoot) { |
| if (rank[aRoot] < rank[bRoot]) { |
| parent[aRoot] = bRoot; |
| } else { |
| parent[bRoot] = aRoot; |
| if (rank[aRoot] == rank[bRoot]) { |
| rank[aRoot]++; |
| } |
| } |
| } |
| } |
| |
| private int find(int a) { |
| int ret = a; |
| while (ret != parent[ret]) { |
| parent[ret] = parent[parent[ret]]; |
| ret = parent[ret]; |
| } |
| return ret; |
| } |
| } |