GenderRescorer.java

/*
 * Source code for listing 5.4
 * 
 */
package mia.recommender.ch05;

import org.apache.mahout.cf.taste.common.TasteException;
import org.apache.mahout.cf.taste.impl.common.FastIDSet;
import org.apache.mahout.cf.taste.model.DataModel;
import org.apache.mahout.cf.taste.model.PreferenceArray;
import org.apache.mahout.cf.taste.recommender.IDRescorer;
import org.apache.mahout.common.iterator.FileLineIterable;

import java.io.File;
import java.io.IOException;

public class GenderRescorer implements IDRescorer {

  private final FastIDSet men;
  private final FastIDSet women;
  private final FastIDSet usersRateMoreMen;
  private final FastIDSet usersRateLessMen;
  private final boolean filterMen;

  public GenderRescorer(FastIDSet men,
                        FastIDSet women,
                        FastIDSet usersRateMoreMen,
                        FastIDSet usersRateLessMen,
                        long userID, DataModel model)
      throws TasteException {
    this.men = men;
    this.women = women;
    this.usersRateMoreMen = usersRateMoreMen;
    this.usersRateLessMen = usersRateLessMen;
    this.filterMen = ratesMoreMen(userID, model);
  }

  public static FastIDSet[] parseMenWomen(File genderFile)
      throws IOException {
    FastIDSet men = new FastIDSet(50000);
    FastIDSet women = new FastIDSet(50000);
    for (String line : new FileLineIterable(genderFile)) {
      int comma = line.indexOf(',');
      char gender = line.charAt(comma + 1);
      if (gender == 'U') {
        continue;
      }
      long profileID = Long.parseLong(line.substring(0, comma));
      if (gender == 'M') {
        men.add(profileID);
      } else {
        women.add(profileID);
      }
    }
    men.rehash();
    women.rehash();
    return new FastIDSet[] { men, women };
  }

  private boolean ratesMoreMen(long userID, DataModel model)
      throws TasteException {
    if (usersRateMoreMen.contains(userID)) {
      return true;
    }
    if (usersRateLessMen.contains(userID)) {
      return false;
    }
    PreferenceArray prefs = model.getPreferencesFromUser(userID);
    int menCount = 0;
    int womenCount = 0;
    for (int i = 0; i < prefs.length(); i++) {
      long profileID = prefs.get(i).getItemID();
      if (men.contains(profileID)) {
        menCount++;
      } else if (women.contains(profileID)) {
        womenCount++;
      }
    }
    boolean ratesMoreMen = menCount > womenCount;
    if (ratesMoreMen) {
      usersRateMoreMen.add(userID);
    } else {
      usersRateLessMen.add(userID);
    }
    return ratesMoreMen;
  }

  @Override
  public double rescore(long profileID, double originalScore) {
    return isFiltered(profileID) ? Double.NaN : originalScore;
  }

  @Override
  public boolean isFiltered(long profileID) {
    return filterMen ? men.contains(profileID) : women.contains(profileID);
  }

}