| /* |
| * 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.sysds.lops.compile; |
| |
| import java.util.Comparator; |
| |
| import org.apache.sysds.lops.Lop; |
| |
| |
| /** |
| * |
| * Comparator class used in sorting the LopDAG in topological order. Refer to |
| * doTopologicalSort_strict_order() in dml/lops/compile/Dag.java |
| * |
| * Topological sort guarantees the following: |
| * |
| * 1) All lops with level i appear before any lop with level greater than i |
| * (source nodes are at level 0) |
| * |
| * 2) Within a given level, nodes are ordered by their ID i.e., by the other in |
| * which they are created |
| * |
| * compare() method is designed to respect the above two requirements. |
| * |
| * @param <N> class extending Lop |
| */ |
| public class LopComparator<N extends Lop> |
| implements Comparator<N> |
| { |
| |
| @Override |
| public int compare(N o1, N o2) { |
| if (o1.getLevel() < o2.getLevel()) |
| return -1; // o1 is less than o2 |
| else if (o1.getLevel() > o2.getLevel()) |
| return 1; // o1 is greater than o2 |
| else { |
| if (o1.getID() < o2.getID()) |
| return -1; // o1 is less than o2 |
| else if (o1.getID() > o2.getID()) |
| return 1; // o1 is greater than o2 |
| else |
| throw new RuntimeException("Unexpected error: ID's of two lops are same."); |
| } |
| } |
| |
| } |