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

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Here is the source code for org.sf.xrime.algorithms.partitions.connected.strongly.ExtractSCC.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 org.apache.hadoop.io.Text;
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.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.vertex.LabeledAdjBiSetVertex;

/**
 * This class is used to extract SCC from a label propagation converged graph. We may need
 * to extend Map-Reduce framework to support multiple output collector, so as to extract 
 * SCC, predecessors, descendants, and reminders in one iteration.
 * @author xue
 *
 */
public class ExtractSCC extends GraphAlgorithm {
    /**
     * Default constructor.
     */
    public ExtractSCC() {
        super();
    }

    /**
     * Mapper. Find those vertexes with both FORWARD_LABEL and BACKWARD_LABEL, which are
     * vertexes inside the SCC. Please recall that, we only propagate label from a single
     * source vertex in one iteration.
     * @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 {
            // the forward label and backward label should be the same.
            if (value.getStringLabel(ConstantLabels.BACKWARD_LABEL) != null
                    && value.getStringLabel(ConstantLabels.FORWARD_LABEL) != null) {
                // Create a new LabeledAdjBiSetVertex.
                LabeledAdjBiSetVertex result = new LabeledAdjBiSetVertex();
                // Set id.
                result.setId(key.toString());
                // Only set this labels.
                result.setStringLabel(ConstantLabels.FINAL_LABEL,
                        value.getStringLabel(ConstantLabels.FORWARD_LABEL));
                output.collect(key, result);
            }
        }
    }

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

        // the keys are vertex identifiers (strings)
        conf.setOutputKeyClass(Text.class);
        // the values are vertexes (Writable)
        conf.setOutputValueClass(LabeledAdjBiSetVertex.class);
        conf.setMapperClass(MapClass.class);
        // No combiners, no reducers.
        // 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(0);

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