/*

  * 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.aggregators.DoubleOverwriteAggregator;

 import org.apache.giraph.graph.BasicComputation;

 import org.apache.giraph.master.DefaultMasterCompute;

 import org.apache.giraph.graph.Vertex;

 import org.apache.giraph.worker.WorkerContext;

 import org.apache.hadoop.io.DoubleWritable;

 import org.apache.hadoop.io.FloatWritable;

 import org.apache.hadoop.io.LongWritable;

 import org.apache.log4j.Logger;

 import java.io.IOException;

 /**

  * Demonstrates a computation with a centralized part implemented via a

  * MasterCompute.

  */

 public class SimpleMasterComputeComputation extends BasicComputation<

     LongWritable, DoubleWritable, FloatWritable, DoubleWritable> {

   /** Aggregator to get values from the master to the workers */

   public static final String SMC_AGG = "simplemastercompute.aggregator";

   /** Logger */

   private static final Logger LOG =

       Logger.getLogger(SimpleMasterComputeComputation.class);

   @Override

   public void compute(

       Vertex<LongWritable, DoubleWritable, FloatWritable> vertex,

       Iterable<DoubleWritable> messages) throws IOException {

     double oldSum = getSuperstep() == 0 ? 0 : vertex.getValue().get();

     double newValue = this.<DoubleWritable>getAggregatedValue(SMC_AGG).get();

     double newSum = oldSum + newValue;

     vertex.setValue(new DoubleWritable(newSum));

     SimpleMasterComputeWorkerContext workerContext = getWorkerContext();

     workerContext.setFinalSum(newSum);

     LOG.info("Current sum: " + newSum);

   }

   /**

    * Worker context used with {@link SimpleMasterComputeComputation}.

    */

   public static class SimpleMasterComputeWorkerContext

       extends WorkerContext {

     /** Final sum value for verification for local jobs */

     private static double FINAL_SUM;

     @Override

     public void preApplication()

       throws InstantiationException, IllegalAccessException {

     }

     @Override

     public void preSuperstep() {

     }

     @Override

     public void postSuperstep() {

     }

     @Override

     public void postApplication() {

     }

     public static void setFinalSum(double sum) {

       FINAL_SUM = sum;

     }

     public static double getFinalSum() {

       return FINAL_SUM;

     }

   }

   /**

    * MasterCompute used with {@link SimpleMasterComputeComputation}.

    */

   public static class SimpleMasterCompute

       extends DefaultMasterCompute {

     @Override

     public void compute() {

       setAggregatedValue(SMC_AGG,

           new DoubleWritable(((double) getSuperstep()) / 2 + 1));

       if (getSuperstep() == 10) {

         haltComputation();

       }

     }

     @Override

     public void initialize() throws InstantiationException,

         IllegalAccessException {

       registerAggregator(SMC_AGG, DoubleOverwriteAggregator.class);

     }

   }

 }