ch.ethz.las.wikimining.mr.coverage.GreeDiReducer.java Source code

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Here is the source code for ch.ethz.las.wikimining.mr.coverage.GreeDiReducer.java

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package ch.ethz.las.wikimining.mr.coverage;

import ch.ethz.las.wikimining.functions.WordCoverageFromMahout;
import ch.ethz.las.wikimining.mr.base.Defaults;
import ch.ethz.las.wikimining.mr.base.DocumentWithVectorWritable;
import ch.ethz.las.wikimining.mr.base.Fields;
import ch.ethz.las.wikimining.sfo.SfoGreedyAlgorithm;
import ch.ethz.las.wikimining.sfo.SfoGreedyLazy;
import java.io.IOException;
import java.util.Set;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.mapreduce.Reducer;

/**
 * Applies the SFO greedy algorithm for word coverage (eq 1) as a Reduce
 * stage, part of the GreeDi protocol.
 *
 * @author Victor Ungureanu (uvictor@student.ethz.ch)
 */
public class GreeDiReducer extends Reducer<IntWritable, DocumentWithVectorWritable, NullWritable, IntWritable> {

    @Override
    public void reduce(IntWritable key, Iterable<DocumentWithVectorWritable> values, Context context)
            throws IOException, InterruptedException {
        final WordCoverageFromMahout objectiveFunction = new WordCoverageFromMahout(values);
        final SfoGreedyAlgorithm sfo = new SfoGreedyLazy(objectiveFunction);
        final int selectCount = context.getConfiguration().getInt(Fields.SELECT_COUNT.get(),
                Defaults.SELECT_COUNT.get());

        Set<Integer> selected = sfo.run(objectiveFunction.getAllDocIds(), selectCount);

        for (Integer docId : selected) {
            IntWritable outValue = new IntWritable(docId);
            context.write(NullWritable.get(), outValue);
        }
    }
}