backwardpruningcallback.java

一个数据挖掘软件ALPHAMINERR的整个过程的JAVA版源代码

/*
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program 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 General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/**
 * Title: XELOPES Data Mining Library
 * Description: The XELOPES library is an open platform-independent and data-source-independent library for Embedded Data Mining.
 * Copyright: Copyright (c) 2002 Prudential Systems Software GmbH
 * Company: ZSoft (www.zsoft.ru), Prudsys (www.prudsys.com)
 * @author Valentine Stepanenko ([e-mail])
 * @version 1.0
 */
package com.prudsys.pdm.Models.Classification.DecisionTree;

import com.prudsys.pdm.Core.*;
import com.prudsys.pdm.Automat.*;

/**
 * Backward pruning callback for iterative decision trees.
 * The iteration with the highest assessment value is used.
 */
public class BackwardPruningCallback extends RetrospectiveCallback
{
  // -----------------------------------------------------------------------
  //  Variables declarations
  // -----------------------------------------------------------------------
  /** Number of iteration step with highest assessment value. */
  private int bestIterationStep = -1;

  /** Backward mode (after forward). */
  private boolean backwardMode  = false;

  /** Number of iteration step in backward mode. */
  private int iterationStepBack = 0;

  /** Debug. 0 - no debugging. */
  private int debug = 1;

  // -----------------------------------------------------------------------
  //  Constructor
  // -----------------------------------------------------------------------
  /**
   * Empty constructor.
   */
  public BackwardPruningCallback()
  {
  }

  // -----------------------------------------------------------------------
  //  Calculate new parameters
  // -----------------------------------------------------------------------
  /**
   * Backward pruning callback.
   *
   * @return status of calculation
   * @exception MiningException algorithm is not iterative one
   */
  protected int runParameterCalculation() throws MiningException {

    System.out.println("assessment = " + currentAssessment);

    // Iterative algorithm handling:
    if ( ! (miningAlgorithm instanceof IterativeMiningAlgorithm) )
      throw new MiningException("Mining algorithm must be iterative.");
    ((IterativeMiningAlgorithm)miningAlgorithm).setIterativeMode(true);

    // Backward mode:
    if (backwardMode) {
      if (iterationStepBack == bestIterationStep)
        return CALCULATION_STATUS_NO_IMPROVEMENT;
      iterationStepBack = iterationStepBack + 1;
    };

    // Decision tree ready => switch to backward mode:
    if ( ! ((IterativeMiningAlgorithm)miningAlgorithm).isIterationImprovement() ) {
      // Find best assessment:
      double maxAssessment = currentAssessment + 0.000001;
      for (int i = 0; i < getNumberOfCallbackSteps(); i++) {
         double assVal = ((Double) allAssessments.elementAt(i)).doubleValue();
         if (assVal > maxAssessment) {
           maxAssessment     = assVal;
           backwardMode      = true;
           bestIterationStep = i;
         };
      };

      // Last iteration step was the best one => no backward mode required:
      if (! backwardMode)
        return CALCULATION_STATUS_NO_IMPROVEMENT;
      // Start backward mode => reset algorithm:
      else {
        if (debug > 0) System.out.println("Switch to backward mode:");
        ((IterativeMiningAlgorithm)miningAlgorithm).resetIterations();
      };
    };

    return CALCULATION_STATUS_SUCCESSFUL;
  }

}