org.sf.xrime.algorithms.statistics.AverageVertexDegree.java Source code

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Here is the source code for org.sf.xrime.algorithms.statistics.AverageVertexDegree.java

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/*
 * Copyright (C) IBM Corp. 2009.
 * 
 * Licensed 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.sf.xrime.algorithms.statistics;

import java.io.IOException;
import java.util.Iterator;

import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.compress.GzipCodec;
import org.apache.hadoop.mapred.FileInputFormat;
import org.apache.hadoop.mapred.FileOutputFormat;
import org.apache.hadoop.mapred.JobClient;
import org.apache.hadoop.mapred.JobConf;
import org.apache.hadoop.mapred.Mapper;
import org.apache.hadoop.mapred.OutputCollector;
import org.apache.hadoop.mapred.Reducer;
import org.apache.hadoop.mapred.Reporter;
import org.apache.hadoop.mapred.SequenceFileInputFormat;
import org.apache.hadoop.util.ToolRunner;
import org.sf.xrime.ProcessorExecutionException;
import org.sf.xrime.algorithms.GraphAlgorithm;
import org.sf.xrime.algorithms.utils.GraphAlgorithmMapReduceBase;
import org.sf.xrime.model.Graph;
import org.sf.xrime.model.vertex.AdjVertex;

/**
 * Calculate average degree of vertexes in the graph.
 */
public class AverageVertexDegree extends GraphAlgorithm {
    /**
     * Default constructor.
     */
    public AverageVertexDegree() {
        super();
    }

    /**
     * Emit the degree of each vertex.
     */
    public static class MapClass extends GraphAlgorithmMapReduceBase
            implements Mapper<Text, AdjVertex, Text, IntWritable> {

        public void map(Text key, AdjVertex value, OutputCollector<Text, IntWritable> output, Reporter reporter)
                throws IOException {
            // Get the degree from the input adjacent vertexes list.
            output.collect(new Text("Average_Degree"),
                    new IntWritable((value.getEdges() == null) ? 0 : value.getEdges().size()));
        }
    }

    /**
     * Calculate the average degree.
     */
    public static class ReduceClass extends GraphAlgorithmMapReduceBase
            implements Reducer<Text, IntWritable, Text, IntWritable> {

        public void reduce(Text key, Iterator<IntWritable> values, OutputCollector<Text, IntWritable> output,
                Reporter reporter) throws IOException {
            int count = 0;
            int sum = 0;
            while (values.hasNext()) {
                count++;
                sum += values.next().get();
            }
            if (count == 0)
                count = 1;
            output.collect(key, new IntWritable(sum / count));
        }
    }

    @Override
    public void setArguments(String[] params) throws ProcessorExecutionException {
        // Make sure there are exactly 2 parameters left.
        if (params.length != 2) {
            throw new ProcessorExecutionException(
                    "Wrong number of parameters: " + params.length + " instead of 2.");
        }

        // Configure the algorithm instance.
        Graph src = new Graph(Graph.defaultGraph());
        src.setPath(new Path(params[0]));
        Graph dest = new Graph(Graph.defaultGraph());
        dest.setPath(new Path(params[1]));

        setSource(src);
        setDestination(dest);
    }

    @Override
    public void execute() throws ProcessorExecutionException {
        JobConf conf = new JobConf(context, AverageVertexDegree.class);
        conf.setJobName("AverageDegree");

        // the keys are a pseudo one ("Average_Degree")
        conf.setOutputKeyClass(Text.class);
        // the values are degrees (ints)
        conf.setOutputValueClass(IntWritable.class);
        conf.setMapperClass(MapClass.class);
        // No combiner is permitted.
        conf.setReducerClass(ReduceClass.class);
        // The format of input data is generated with WritableSerialization.
        conf.setInputFormat(SequenceFileInputFormat.class);
        try {
            FileInputFormat.setInputPaths(conf, getSource().getPath());
            FileOutputFormat.setOutputPath(conf, getDestination().getPath());
        } catch (IllegalAccessException e1) {
            throw new ProcessorExecutionException(e1);
        }
        conf.setNumMapTasks(getMapperNum());
        // Only one reducer is permitted, or the average value will be wrong.
        conf.setNumReduceTasks(1);
        conf.setCompressMapOutput(true);
        conf.setMapOutputCompressorClass(GzipCodec.class);

        try {
            this.runningJob = JobClient.runJob(conf);
        } catch (IOException e) {
            throw new ProcessorExecutionException(e);
        }
    }

    public static void main(String[] args) {
        try {
            int res = ToolRunner.run(new AverageVertexDegree(), args);
            System.exit(res);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}