/*

  * 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.giraph.examples;

 import org.apache.giraph.graph.BasicComputation;

 import org.apache.giraph.graph.Vertex;

 import org.apache.hadoop.io.IntWritable;

 import org.apache.hadoop.io.NullWritable;

 import java.io.IOException;

 /**

  * Simple algorithm that computes the max value in the graph.

  */

 public class MaxComputation extends BasicComputation<IntWritable, IntWritable,

     NullWritable, IntWritable> {

   @Override

   public void compute(Vertex<IntWritable, IntWritable, NullWritable> vertex,

       Iterable<IntWritable> messages) throws IOException {

     boolean changed = false;

     for (IntWritable message : messages) {

       if (vertex.getValue().get() < message.get()) {

         vertex.setValue(message);

         changed = true;

       }

     }

     if (getSuperstep() == 0 || changed) {

       sendMessageToAllEdges(vertex, vertex.getValue());

     }

     vertex.voteToHalt();

   }

 }