SquaredErrorCostFunction.h

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// -*- C++ -*-

// PLearn (A C++ Machine Learning Library)
// Copyright (C) 1998 Pascal Vincent
// Copyright (C) 1999-2002 Pascal Vincent, Yoshua Bengio, Rejean Ducharme and University of Montreal
// Copyright (C) 2001-2002 Nicolas Chapados, Ichiro Takeuchi, Jean-Sebastien Senecal
// Copyright (C) 2002 Xiangdong Wang, Christian Dorion

// 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.
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//  2. Redistributions in binary form must reproduce the above copyright
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//     documentation and/or other materials provided with the distribution.
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/* *******************************************************      
   * $Id: SquaredErrorCostFunction.h,v 1.5 2004/04/07 23:15:17 morinf Exp $
   * This file is part of the PLearn library.
   ******************************************************* */

#ifndef SquaredErrorCostFunction_INC
#define SquaredErrorCostFunction_INC

#include "Kernel.h"

namespace PLearn {
using namespace std;



class SquaredErrorCostFunction: public Kernel
{
  typedef Kernel inherited;
                
protected:
  int targetindex;
  bool classification;
  real hotvalue, coldvalue;

public:
  SquaredErrorCostFunction(int the_targetindex=-1)
    :targetindex(the_targetindex), classification(false), hotvalue(1), coldvalue(0) {};

  SquaredErrorCostFunction(real hot_value, real cold_value)
    : targetindex(-1), classification(true), hotvalue(hot_value), coldvalue(cold_value) {};

  PLEARN_DECLARE_OBJECT(SquaredErrorCostFunction);

  virtual string info() const
        { return "squared_error"; }

  virtual real evaluate(const Vec& output, const Vec& target) const; 

protected:
  static void declareOptions(OptionList &ol);
};

DECLARE_OBJECT_PTR(SquaredErrorCostFunction);

inline CostFunc squared_classification_error(real hot_value=0.8, real cold_value=0.2)
{
  return new SquaredErrorCostFunction(hot_value, cold_value);
}

inline CostFunc squared_error(int singleoutputindex=-1);

} // end of namespace PLearn

#endif

---