org.apache.mahout.ga.watchmaker.MahoutEvaluator.java Source code

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Here is the source code for org.apache.mahout.ga.watchmaker.MahoutEvaluator.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.mahout.ga.watchmaker;

import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.Collection;

import com.google.common.io.Closeables;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataOutputStream;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.SequenceFileOutputFormat;
import org.apache.mahout.common.HadoopUtil;
import org.apache.mahout.common.StringUtils;
import org.uncommons.watchmaker.framework.FitnessEvaluator;

/**
 * Generic Mahout distributed evaluator. takes an evaluator and a population and launches a Hadoop job. The
 * job evaluates the fitness of each individual of the population using the given evaluator. Takes care of
 * storing the population into an input file, and loading the fitness from job outputs.
 */
public final class MahoutEvaluator {

    private MahoutEvaluator() {
    }

    /**
     * Uses Mahout to evaluate every candidate from the input population using the given evaluator.
     *
     * @param evaluator
     *          FitnessEvaluator to use
     * @param population
     *          input population
     * @param evaluations
     *          {@code List<Double>} that contains the evaluated fitness for each candidate from the
     *          input population, sorted in the same order as the candidates.
     */
    public static void evaluate(FitnessEvaluator<?> evaluator, Iterable<?> population,
            Collection<Double> evaluations, Path input, Path output)
            throws IOException, ClassNotFoundException, InterruptedException {

        Job job = new Job();
        job.setJarByClass(MahoutEvaluator.class);

        Configuration conf = job.getConfiguration();

        FileSystem fs = FileSystem.get(conf);
        HadoopUtil.delete(conf, input);
        HadoopUtil.delete(conf, output);

        storePopulation(fs, new Path(input, "population"), population);

        configureJob(job, conf, evaluator, input, output);
        job.waitForCompletion(true);

        OutputUtils.importEvaluations(fs, conf, output, evaluations);
    }

    /**
     * Configure the job
     *
     * @param evaluator
     *          FitnessEvaluator passed to the mapper
     * @param inpath
     *          input {@code Path}
     * @param outpath
     *          output {@code Path}
     */
    private static void configureJob(Job job, Configuration conf, FitnessEvaluator<?> evaluator, Path inpath,
            Path outpath) {

        conf.set("mapred.input.dir", inpath.toString());
        conf.set("mapred.output.dir", outpath.toString());

        job.setOutputKeyClass(LongWritable.class);
        job.setOutputValueClass(DoubleWritable.class);

        job.setMapperClass(EvalMapper.class);

        job.setInputFormatClass(TextInputFormat.class);
        job.setOutputFormatClass(SequenceFileOutputFormat.class);

        // store the stringified evaluator
        conf.set(EvalMapper.MAHOUT_GA_EVALUATOR, StringUtils.toString(evaluator));
    }

    /**
     * Stores a population of candidates in the output file path.
     * 
     * @param fs
     *          FileSystem used to create the output file
     * @param f
     *          output file path
     * @param population
     *          population to store
     */
    static void storePopulation(FileSystem fs, Path f, Iterable<?> population) throws IOException {
        FSDataOutputStream out = fs.create(f);
        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(out));

        try {
            for (Object candidate : population) {
                writer.write(StringUtils.toString(candidate));
                writer.newLine();
            }
        } finally {
            Closeables.closeQuietly(writer);
        }
    }

}