examplestream.java

Boosting算法软件包

package jboost.tokenizer;

import java.io.IOException;

import jboost.examples.Attribute;
import jboost.examples.Example;
import jboost.examples.ExampleDescription;
import jboost.examples.Label;
import jboost.examples.RealAttribute;
import jboost.monitor.Monitor;

/**
 * Transforms a set of input data files into a stream of memory-based examples
 * @author: alon orlitsky (re-written by Nigel Duffy 9/8/00)
 * @version: $Header: /cvsroot/jboost/jboost/src/jboost/tokenizer/ExampleStream.java,v 1.1.1.1 2007/05/16 04:06:02 aarvey Exp $
 */
public class ExampleStream {
  
  /**
   *  Constructor. Takes a DataStream which in turn knows how to read specific
   *  data and specification formats.
   *
   *  @param DataStream Stream from underlying data source, produces a stream of 
   *         textual attribute lists.							
   */
  public ExampleStream(DataStream dstream) {
    ds=dstream;
    maxBadAtt=ds.maxBadAtt;
    maxBadExa=ds.maxBadExa;
    numBadAtt=0;
    numBadExa=0;
  }
  
  /** 
   * Get the example description.
   * @return exampleDescription 						 	
   */
  public ExampleDescription getExampleDescription() {
    return(ds.ed);
  }
  
  /** 
   * Returns the example corresponding to a given object
   *
   *  @param o the object to create an example for
   *  @return example corresponding to object						
   */
  public Example getExample(Object o) throws ParseException {
    
    String[] exaText=null;
    Example retval=null;
    try {
      exaText=ds.getExampleText(o);
      if(exaText==null) {
        return(null);
      }
      retval = parseExampleText(exaText);
    }
    catch (BadExaException e) { // bad example
      System.err.println("BadExaException at data item " +o);
      Monitor.log("BadExaException at data item " +o);
    }
    return(retval);
  }
  
  
  /**
   *  Sequentially goes through examples and returns the next good one, 
   *  null if none found. 
   *
   *  @return next good example 							
   */
  public Example getExample() throws ParseException {
    
    String[] exaText=null;
    Example retval=null;
    while(retval==null) {
      try {
        exaText=ds.getExampleText();
        if(exaText==null) {
          break;
        }
        retval = parseExampleText(exaText);
      }
      catch (BadExaException e) { // bad example
        System.err.println("BadExaException " + "Example beginning at line " 
                            + ds.getLineNumber() + "\n" + e.getMessage());
        Monitor.log("BadExaException " + "Example beginning at line " 
                    + ds.getLineNumber() + "\n" + e.getMessage());
        numBadExa++;
        if (numBadExa>maxBadExa) {
          throw new BadDataFileException("More than " + maxBadExa 
                                       + " bad examples.",ds.getLineNumber());
        }
      }
    }
    return(retval);
  }
  
  /**
   * Transforms an array of strings (recieved from a DataStream) into
   *  an Example
   * If the ExampleDescription has the useSamplingWeights flag set to true,
   * then this method will ignore any attributes named DataStream.WEIGHT_ATTR
   * @param exaText text of an example
   * @return example
   */
  public Example parseExampleText(String[] exaText) throws BadExaException {
    if (Monitor.logLevel>3) { 
      Monitor.log("ExampleStream.parseExampleText Parsing Example:");
    }
    
    int numAtt = ds.ed.getNoOfAttributes();
    Attribute[] attArray = new Attribute[numAtt];
    Label label=null;
    double weight= 1.0;
    numBadAtt=0;
    int labelIndex= ds.ed.getLabelIndex();
    int weightIndex= ds.ed.getWeightIndex();
    
    // iterate through each attribute
    // if the attribute is the 'label' or the 'weight' then grab its value
    // otherwise, add it to the attribute array    
    for (int i=0, j=0; i < exaText.length; i++) { 
      try {
        if (i == labelIndex) {
          label= (Label) ds.ed.getLabelDescription().str2Att(exaText[i]);          
        } else if (i == weightIndex) {
          weight= ((RealAttribute) ds.ed.getWeightDescription().str2Att(exaText[i])).getValue();
        } else {
          if (Monitor.logLevel>3) { 
            Monitor.log(ds.ed.getAttributeDescription(j).getAttributeName() 
                        + ":" + exaText[i]);
          }
          attArray[j] = ds.ed.getAttributeDescription(j).str2Att(exaText[i]);
          j++;
        }
      } catch (BadAttException e) {
        System.err.println("BadAttException: Line " + ds.getLineNumber()
            + "\n" + e.getMessage() + "\nContinuing to parse example.");
        e.printStackTrace();
        numBadAtt++;
        if (numBadAtt > maxBadAtt) {
          throw new BadExaException ("Number of bad attributes in example exceeds " 
              + maxBadAtt + " skipping rest of example.", 
              ds.getLineNumber());
        }
        attArray[j++]=null;
      }
    } // found all attributes

    return new Example(attArray, label, weight, ds.ed);
  }
  
//-------------------------------- Private Members ----------------------------//
  
  /** Maximum allowed number of bad attributes in a single example 		*/
  private int maxBadAtt;
  /** Maximum allowed number of bad examples in a data stream			*/
  private int maxBadExa;
  /** Number of bad attributes in the current example				*/
  private int numBadAtt;
  /** Number of bad examples in the current datastream			*/
  private int numBadExa;
  /** The stream of examples in textual form.					*/
  private DataStream ds;
  
//-------------------------------- Test Code ----------------------------------//
  
  
  /** Tests ExampleStream. Run as:
   *  <p>
   *	java ExampleStream filename 
   *  <p>
   *	where filename is a name of a data file.  				*/
  public static void main(String[] args) throws Exception {
    try {mainCore(args);}
    catch (IOException e) {
      System.err.println("IO exception: " + e.getMessage());
      e.printStackTrace();
    }
    catch (RuntimeException e) {
      System.err.println("Runtime exception: " + e.getMessage());
      e.printStackTrace();
    }
  }
  
  public static void mainCore(String[] args) throws IOException, Exception {
    
 /*   Example nextExa;
    
    if (args.length != 1) // wrong number of arguments 
      throw new RuntimeException("Usage: ExampleStream <stem>");
    
    DataStream ds=new jboost_DataStream(true,args[0]);
    
    ExampleStream es = new ExampleStream(ds);
    
    try {
      while ((nextExa=es.getExample()) != null)
        if(Monitor.logLevel>3) Monitor.log(ds.ed.toString(nextExa));
    }
    catch (BadDataFileException e) {
      System.err.println("BadDataFileException\n" + e.getMessage());
    } 
    //	es.finalize;
    
    // if(Monitor.logLevel>3) Monitor.log("Parsing train file.");
    
    // ExampleStream es = new ExampleStream(ed, args[0] + ".train");
    // while ( (nextExa=es.getExample()) != null)
    //    if(Monitor.logLevel>3) Monitor.log(ed.toString(nextExa));
    //es.finalize;*/
  }
}