org.apache.hama.examples.MindistSearch.java Source code

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Here is the source code for org.apache.hama.examples.MindistSearch.java

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/**
 * 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.hama.examples;

import java.io.IOException;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hama.HamaConfiguration;
import org.apache.hama.bsp.Combiner;
import org.apache.hama.bsp.HashPartitioner;
import org.apache.hama.bsp.TextInputFormat;
import org.apache.hama.bsp.TextOutputFormat;
import org.apache.hama.graph.Edge;
import org.apache.hama.graph.GraphJob;
import org.apache.hama.graph.Vertex;
import org.apache.hama.graph.VertexInputReader;

import com.google.common.base.Optional;

/**
 * Finding the mindist vertex in a connected component.
 */
public class MindistSearch {

    /*
     * Make sure that you know that you're comparing text, and not integers!
     */
    public static class MindistSearchVertex extends Vertex<Text, NullWritable, Text> {

        @Override
        public void compute(Iterable<Text> messages) throws IOException {
            Text currentComponent = getValue();
            if (getSuperstepCount() == 0L) {
                // if we have no associated component, pick the lowest in our direct
                // neighbourhood.
                if (currentComponent == null) {
                    setValue(new Text(getVertexID()));
                    for (Edge<Text, NullWritable> e : getEdges()) {
                        Text id = getVertexID();
                        if (id.compareTo(e.getDestinationVertexID()) > 0) {
                            setValue(e.getDestinationVertexID());
                        }
                    }
                    sendMessageToNeighbors(getValue());
                }
            } else {
                boolean updated = false;
                for (Text next : messages) {
                    if (currentComponent != null && next != null) {
                        if (currentComponent.compareTo(next) > 0) {
                            updated = true;
                            setValue(next);
                        }
                    }
                }
                if (updated) {
                    sendMessageToNeighbors(getValue());
                } else {
                    this.voteToHalt();
                }
            }
        }

    }

    public static class MindistSearchTextReader
            extends VertexInputReader<LongWritable, Text, Text, NullWritable, Text> {

        @Override
        public boolean parseVertex(LongWritable key, Text value, Vertex<Text, NullWritable, Text> vertex)
                throws Exception {
            String[] split = value.toString().split("\t");
            for (int i = 0; i < split.length; i++) {
                if (i == 0) {
                    vertex.setVertexID(new Text(split[i]));
                } else {
                    vertex.addEdge(new Edge<Text, NullWritable>(new Text(split[i]), null));
                }
            }
            return true;
        }

    }

    public static class MinTextCombiner extends Combiner<Text> {

        @Override
        public Text combine(Iterable<Text> messages) {
            Text min = null;
            for (Text m : messages) {
                if (min == null || min.compareTo(m) > 0) {
                    min = m;
                }
            }
            return min;
        }

    }

    private static void printUsage() {
        System.out.println("Usage: <input> <output> [maximum iterations (default 30)] [tasks]");
        System.exit(-1);
    }

    public static GraphJob getJob(String inpath, String outpath, Optional<Integer> numTasks,
            Optional<Integer> numIterations) throws IOException {

        HamaConfiguration conf = new HamaConfiguration(new Configuration());
        GraphJob job = new GraphJob(conf, MindistSearchVertex.class);
        job.setJobName("Mindist Search");

        job.setVertexClass(MindistSearchVertex.class);
        job.setInputPath(new Path(inpath));
        job.setOutputPath(new Path(outpath));
        // set the min text combiner here
        job.setCombinerClass(MinTextCombiner.class);

        // set the defaults
        job.setMaxIteration(30);
        if (numTasks.isPresent())
            job.setNumBspTask(numTasks.get());
        if (numIterations.isPresent())
            job.setMaxIteration(numIterations.get());

        job.setVertexIDClass(Text.class);
        job.setVertexValueClass(Text.class);
        job.setEdgeValueClass(NullWritable.class);

        job.setInputFormat(TextInputFormat.class);
        job.setInputKeyClass(LongWritable.class);
        job.setInputValueClass(Text.class);
        job.setVertexInputReaderClass(MindistSearchTextReader.class);

        job.setPartitioner(HashPartitioner.class);
        job.setOutputFormat(TextOutputFormat.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Text.class);
        return job;
    }

    public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {
        if (args.length < 2)
            printUsage();

        Optional<Integer> absent = Optional.absent();
        GraphJob job = getJob(args[0], args[1], args.length >= 3 ? Optional.of(Integer.parseInt(args[3])) : absent,
                args.length >= 4 ? Optional.of(Integer.parseInt(args[4])) : absent);

        long startTime = System.currentTimeMillis();
        if (job.waitForCompletion(true)) {
            System.out.println("Job Finished in " + (System.currentTimeMillis() - startTime) / 1000.0 + " seconds");
        }
    }
}