AdaBoost.h

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// -*- C++ -*-

// AdaBoost.h
//
// Copyright (C) 2003  Pascal Vincent 
// 
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
// 
//  1. Redistributions of source code must retain the above copyright
//     notice, this list of conditions and the following disclaimer.
// 
//  2. Redistributions in binary form must reproduce the above copyright
//     notice, this list of conditions and the following disclaimer in the
//     documentation and/or other materials provided with the distribution.
// 
//  3. The name of the authors may not be used to endorse or promote
//     products derived from this software without specific prior written
//     permission.
// 
// THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
// OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
// NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
// TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
// LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
// SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// 
// This file is part of the PLearn library. For more information on the PLearn
// library, go to the PLearn Web site at www.plearn.org

/* *******************************************************      
   * $Id: AdaBoost.h,v 1.4 2004/07/21 16:30:55 chrish42 Exp $
   ******************************************************* */

// Authors: Yoshua Bengio

#ifndef AdaBoost_INC
#define AdaBoost_INC

#include <plearn_learners/generic/PLearner.h>

namespace PLearn {
using namespace std;

class AdaBoost: public PLearner
{
public:
  typedef PLearner inherited;
  
protected:
  // local variables:

  // average weighted error of each learner
  Vec learners_error;
  // weighing scheme over examples
  Vec example_weights;

  // *********************
  // * protected options *
  // *********************

  // saved options:
  // (unnormalized) weight associated to each weak learner
  Vec voting_weights;
  real sum_voting_weights; // = sum(voting_weights);
  real initial_sum_weights;

  TVec< PP<PLearner> > weak_learners;
  
public:

  // ************************
  // * public build options *
  // ************************

  PP<PLearner> weak_learner_template;

  // normally 0.5
  real target_error;

  // whether to give an expdir to the underlying weak learners
  bool provide_learner_expdir;
  
  // threshold on output of weak learner to decide if class 0 or class 1
  real output_threshold;

  // whether to compute training error during training
  bool compute_training_error;

  // use more refined training criterion when weak classifier is soft
  bool pseudo_loss_adaboost;

  // use resampling (vs weighting) to train the underlying classifier
  bool weight_by_resampling;

  // stop if weak learner does not seem to help
  bool early_stopping;

  // save model after each stage into <expdir>/model.psave
  bool save_often;

  // ****************
  // * Constructors *
  // ****************

  // Default constructor, make sure the implementation in the .cc
  // initializes all fields to reasonable default values.
  AdaBoost();


  // ******************
  // * PLearner methods *
  // ******************

private: 
  // (Please implement in .cc)
  void build_();

protected: 
  // (Please implement in .cc)
  static void declareOptions(OptionList& ol);

public:

  // ************************
  // **** Object methods ****
  // ************************

  virtual void build();

  virtual void makeDeepCopyFromShallowCopy(map<const void*, void*>& copies);

  // Declares other standard object methods
  //  If your class is not instantiatable (it has pure virtual methods)
  // you should replace this by PLEARN_DECLARE_ABSTRACT_OBJECT_METHODS 
  PLEARN_DECLARE_OBJECT(AdaBoost);


  // **************************
  // **** PLearner methods ****
  // **************************

  virtual int outputsize() const;

  virtual void forget();

    
  virtual void train();


  virtual void computeOutput(const Vec& input, Vec& output) const;

  virtual void computeCostsFromOutputs(const Vec& input, const Vec& output, 
                                       const Vec& target, Vec& costs) const;
                                

  virtual TVec<string> getTestCostNames() const;

  virtual TVec<string> getTrainCostNames() const;

};

// Declares a few other classes and functions related to this class
  DECLARE_OBJECT_PTR(AdaBoost);
  
} // end of namespace PLearn

#endif

---