1/*2 * Licensed to the Apache Software Foundation (ASF) under one3 * or more contributor license agreements. See the NOTICE file4 * distributed with this work for additional information5 * regarding copyright ownership. The ASF licenses this file6 * to you under the Apache License, Version 2.0 (the7 * "License"); you may not use this file except in compliance8 * with the License. You may obtain a copy of the License at9 *10 * http://www.apache.org/licenses/LICENSE-2.011 *12 * Unless required by applicable law or agreed to in writing, software13 * 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 and16 * limitations under the License.17 */18package org.apache.giraph.combiner;
1920import org.apache.giraph.types.ops.NumericTypeOps;
21import org.apache.hadoop.io.Writable;
22import org.apache.hadoop.io.WritableComparable;
2324/**25 * Keeps only the message with minimum value.26 *27 * @param <I> Vertex id28 * @param <M> Message29 */30publicclass MinMessageCombiner<I extends WritableComparable,
31 M extends Writable> implements MessageCombiner<I, M> {
32/** Numeric type ops for the value to combine */33privatefinal NumericTypeOps<M> numTypeOps;
3435/**36 * Combiner37 *38 * @param numTypeOps Type ops to use39 */40publicMinMessageCombiner(NumericTypeOps<M> numTypeOps) {
41this.numTypeOps = numTypeOps;
42 }
4344 @Override
45publicvoid combine(I vertexId, M originalMessage, M messageToCombine) {
46if (numTypeOps.compare(originalMessage, messageToCombine) > 0) {
47 numTypeOps.set(originalMessage, messageToCombine);
48 }
49 }
5051 @Override
52public M createInitialMessage() {
53returnthis.numTypeOps.createMaxPositiveValue();
54 }
55 }