CommitteeLearner.java :  » Natural-Language-Processing » MinorThird » edu » cmu » minorthird » classify » algorithms » active » Java Open Source

package edu.cmu.minorthird.classify.algorithms.active;

import edu.cmu.minorthird.classify.*;
import org.apache.log4j.Logger;

import java.util.Random;

/**
 * Routines for forming and working with committees.
 *
 * @author William Cohen
 */

public class CommitteeLearner 
{
  static private Logger log = Logger.getLogger(CommitteeLearner.class);

  private BatchClassifierLearner learner;
  private int committeeSize; 

  public CommitteeLearner(BatchClassifierLearner learner,int committeeSize)
  {
    this.learner = learner;
    this.committeeSize = committeeSize;
  }

  /** Learn a committee */
  public Classifier[] batchTrainCommittee(RandomAccessDataset data)
  {
    // build the committee
    Classifier[] committee = new Classifier[committeeSize]; 
      
    Random rand = new Random(0);
    for (int i=0; i<committee.length; i++) {
      Dataset ithBag = bag(rand,data); 
      log.info("training committee member on "+ithBag.size()+" examples");
      committee[i] = learner.batchTrain( ithBag );
      log.info("committee member #"+i+":\n"+committee[i]);
    }
    return committee;
  }
  
  private Dataset bag(Random r,RandomAccessDataset data)
  {
    Dataset result = new BasicDataset(); 
    for (int i=0; i<data.size(); i++) {
      int k = (int) (r.nextDouble()*data.size());
      log.debug("bag: add example #"+k+": "+data.getExample(k));
      result.add( data.getExample(k) );
    }
    return result;
  }
}