FileEventStream.java

///////////////////////////////////////////////////////////////////////////////
//Copyright (C) 2005 Thomas Morton
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
//////////////////////////////////////////////////////////////////////////////   
package opennlp.maxent;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

import opennlp.maxent.io.SuffixSensitiveGISModelWriter;

/** 
 * Class for using a file of events as an event stream.  The format of the file is one event perline with
 * each line consisting of outcome followed by contexts (space delimited).
 * @author Tom Morton
 *
 */
public class FileEventStream implements EventStream {

  BufferedReader reader;
  String line;
  
  /**
   * Creates a new file event stream from the specified file name.
   * @param fileName the name fo the file containing the events.
   * @throws IOException When the specified file can not be read.
   */
  public FileEventStream(String fileName, String encoding) throws IOException {
    if (encoding == null) {
      reader = new BufferedReader(new FileReader(fileName));
    }
    else {
      reader = new BufferedReader(new InputStreamReader(new FileInputStream(fileName),encoding));
    }
  }
  
  public FileEventStream(String fileName) throws IOException {
    this(fileName,null);
  }
    
  /**
   * Creates a new file event stream from the specified file.
   * @param file the file containing the events.
   * @throws IOException When the specified file can not be read.
   */
  public FileEventStream(File file) throws IOException {
    reader = new BufferedReader(new InputStreamReader(new FileInputStream(file),"UTF8"));
  }
  
  public boolean hasNext() {
    try {
      return (null != (line = reader.readLine()));
    }
    catch (IOException e) {
      System.err.println(e);
      return (false);
    }
  }
  
  public Event nextEvent() {
    StringTokenizer st = new StringTokenizer(line);
    String outcome = st.nextToken();
    int count = st.countTokens();
    String[] context = new String[count];
    for (int ci = 0; ci < count; ci++) {
      context[ci] = st.nextToken();
    }
    return (new Event(outcome, context));
  }
  
  /**
   * Generates a string representing the specified event.
   * @param event The event for which a string representation is needed.
   * @return A string representing the specified event.
   */
  public static String toLine(Event event) {
    StringBuffer sb = new StringBuffer();
    sb.append(event.getOutcome());
    String[] context = event.getContext();
    for (int ci=0,cl=context.length;ci<cl;ci++) {
      sb.append(" "+context[ci]);
    }
    sb.append(System.getProperty("line.separator"));
    return sb.toString();
  }
  
  /**
   * Trains and writes a model based on the events in the specified event file.
   * the name of the model created is based on the event file name.
   * @param args eventfile [iterations cuttoff]
   * @throws IOException when the eventfile can not be read or the model file can not be written.
   */
  public static void main(String[] args) throws IOException {
    if (args.length == 0) {
      System.err.println("Usage: FileEventStream eventfile [iterations cutoff]");
      System.exit(1);
    }
    int ai=0;
    String eventFile = args[ai++];
    EventStream es = new FileEventStream(eventFile);
    int iterations = 100;
    int cutoff = 5;
    if (ai < args.length) {
      iterations = Integer.parseInt(args[ai++]);
      cutoff = Integer.parseInt(args[ai++]);
    }
    GISModel model = GIS.trainModel(es,iterations,cutoff);
    new SuffixSensitiveGISModelWriter(model, new File(eventFile+".bin.gz")).persist();
  }
}