org.sf.xrime.algorithms.partitions.connected.strongly.ForwardTrimPartB.java Source code

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Here is the source code for org.sf.xrime.algorithms.partitions.connected.strongly.ForwardTrimPartB.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.partitions.connected.strongly;

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

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.mapred.SequenceFileOutputFormat;
import org.sf.xrime.ProcessorExecutionException;
import org.sf.xrime.algorithms.GraphAlgorithm;
import org.sf.xrime.algorithms.utils.GraphAlgorithmMapReduceBase;
import org.sf.xrime.model.edge.AdjVertexEdge;
import org.sf.xrime.model.vertex.LabeledAdjBiSetVertex;

/**
 * The forward trim is to trim vertexes which have no ancestors. This class is used to do the
 * real trim.
 * @author xue
 */
public class ForwardTrimPartB extends GraphAlgorithm {
    /**
     * Default constructor.
     */
    public ForwardTrimPartB() {
        super();
    }

    /**
     * Mapper.
     * @author xue
     */
    public static class MapClass extends GraphAlgorithmMapReduceBase
            implements Mapper<Text, LabeledAdjBiSetVertex, Text, LabeledAdjBiSetVertex> {

        @Override
        public void map(Text key, LabeledAdjBiSetVertex value, OutputCollector<Text, LabeledAdjBiSetVertex> output,
                Reporter reporter) throws IOException {
            if (value.getBackwardVertexes() == null || value.getBackwardVertexes().size() == 0) {
                // This vertex has no ancestors. Notify its descendants about this. Furthermore,
                // this vertex will be trimmed.
                for (AdjVertexEdge descendant : value.getForwardVertexes()) {
                    LabeledAdjBiSetVertex notifier = new LabeledAdjBiSetVertex();
                    notifier.setId(descendant.getOpposite());
                    // Tell the descendant that the edge from this ancestor should be removed.
                    notifier.setStringLabel(ConstantLabels.ANCESTOR_TO_BE_REMOVED, key.toString());
                    // Just tell the descendant.
                    output.collect(new Text(descendant.getOpposite()), notifier);
                }
            } else {
                // This vertex is a normal vertex, emit it.
                output.collect(key, value);
            }
        }
    }

    /**
     * Reducer.
     * @author xue
     */
    public static class ReduceClass extends GraphAlgorithmMapReduceBase
            implements Reducer<Text, LabeledAdjBiSetVertex, Text, LabeledAdjBiSetVertex> {

        @Override
        public void reduce(Text key, Iterator<LabeledAdjBiSetVertex> values,
                OutputCollector<Text, LabeledAdjBiSetVertex> output, Reporter reporter) throws IOException {
            // Ancestors to be removed.
            HashSet<String> ancestors_to_be_removed = new HashSet<String>();
            // This vertex - a descendant of those ancestors.
            LabeledAdjBiSetVertex descendant = null;
            while (values.hasNext()) {
                LabeledAdjBiSetVertex curr_vertex = values.next();
                if (curr_vertex.getStringLabel(ConstantLabels.ANCESTOR_TO_BE_REMOVED) == null) {
                    // Clone the vertex for later use. NOT deep clone.
                    descendant = new LabeledAdjBiSetVertex(curr_vertex);
                } else {
                    // Accummulate the ancestors to be removed.
                    ancestors_to_be_removed.add(curr_vertex.getStringLabel(ConstantLabels.ANCESTOR_TO_BE_REMOVED));
                }
            }
            if (descendant != null) {
                for (String ancestor : ancestors_to_be_removed) {
                    // Remove edges to ancestors to be removed.
                    descendant.getBackwardVertexes().remove(new AdjVertexEdge(ancestor));
                }
                // Collect this updated vertex.
                output.collect(key, descendant);
            }
        }
    }

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

        // the keys are vertex identifiers (strings)
        conf.setOutputKeyClass(Text.class);
        // the values are vertexes (Writable)
        conf.setOutputValueClass(LabeledAdjBiSetVertex.class);
        conf.setMapperClass(MapClass.class);
        // No combiner is permitted.
        conf.setReducerClass(ReduceClass.class);
        // makes the file format suitable for machine processing.
        conf.setInputFormat(SequenceFileInputFormat.class);
        conf.setOutputFormat(SequenceFileOutputFormat.class);
        try {
            FileInputFormat.setInputPaths(conf, getSource().getPath());
            FileOutputFormat.setOutputPath(conf, getDestination().getPath());
        } catch (IllegalAccessException e1) {
            throw new ProcessorExecutionException(e1);
        }
        conf.setNumMapTasks(getMapperNum());
        conf.setNumReduceTasks(getReducerNum());
        conf.setCompressMapOutput(true);
        conf.setMapOutputCompressorClass(GzipCodec.class);

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