1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the 7 * "License"); you may not use this file except in compliance 8 * with the License. You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 19 package org.apache.giraph.aggregators; 20 21 import org.apache.hadoop.io.DoubleWritable; 22 23 /** 24 * Aggregator that stores a value that is overwritten once another value is 25 * aggregated. This aggregator is useful for one-to-many communication from 26 * master.compute() or from a special vertex. In case multiple vertices write 27 * to this aggregator, its behavior is non-deterministic. 28 */ 29 public class DoubleOverwriteAggregator extends 30 BasicAggregator<DoubleWritable> { 31 @Override 32 public void aggregate(DoubleWritable value) { 33 getAggregatedValue().set(value.get()); 34 } 35 36 @Override 37 public DoubleWritable createInitialValue() { 38 return new DoubleWritable(0); 39 } 40 }