code: package edu.jhu.thrax.hadoop.features;
  
  import java.util.Map;
  
  import org.apache.hadoop.io.FloatWritable;
  import org.apache.hadoop.io.Writable;
  
  import edu.jhu.thrax.hadoop.datatypes.RuleWritable;
  import edu.jhu.thrax.util.Vocabulary;
  
  public class CharacterCompressionRatioFeature implements SimpleFeature {
  
    private static final FloatWritable ZERO = new FloatWritable(0f);
  
    public static final String NAME = "char_cr";
    
    public Writable score(RuleWritable r) {
      int src_length = 0;
      for (int tok : r.source) {
        if (!Vocabulary.nt(tok)) {
          src_length += Vocabulary.word(tok).length();
        }
      }
      src_length += r.source.length - 1;
  
      int tgt_length = 0;
      for (int tok : r.target) {
        if (!Vocabulary.nt(tok)) {
          tgt_length += Vocabulary.word(tok).length();
        }
      }
      tgt_length += r.target.length - 1;
  
      if (src_length == 0 || tgt_length == 0)
        return ZERO;
      else
        return new FloatWritable((float) Math.log((float) tgt_length / src_length));
    }
    
    public String getName() {
      return NAME;
    }
  
    public void unaryGlueRuleScore(int nt, Map<Integer, Writable> map) {
      map.put(Vocabulary.id(NAME), ZERO);
    }
  
    public void binaryGlueRuleScore(int nt, Map<Integer, Writable> map) {
      map.put(Vocabulary.id(NAME), ZERO);
    }
  }
  