LiftBinaryCostFunction.cc

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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

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/* *******************************************************      
   * $Id: LiftBinaryCostFunction.cc,v 1.4 2004/04/07 23:15:17 morinf Exp $
   * This file is part of the PLearn library.
   ******************************************************* */

#include "LiftBinaryCostFunction.h"

namespace PLearn {
using namespace std;


PLEARN_IMPLEMENT_OBJECT(LiftBinaryCostFunction, "ONE LINE DESCR", "NO HELP");

real LiftBinaryCostFunction::evaluate(const Vec& output, const Vec& target) const
{
  int len = output.length();
  if ((target.length()!=1 && target.length()!=2) || len>2)
    PLERROR("For binary problems, the output and binary vectors must have length 1 or 2 (%d)", len);

  if (len == 1)
  {
    real out0 = output[0];
    if (make_positive_output) out0 = sigmoid(out0);
    return (target[0]>0.5) ? out0 : -out0;
  }
  else
  {
    real out1 = output[1];
    if (make_positive_output) out1 = sigmoid(out1);
    if (target.length()==2)
      return (target[1]>target[0]) ? out1 : -out1;
    else
      return (target[0]>0.5) ? out1 : -out1;
  }

  return 0.0;  // to make the compiler happy...
}

void LiftBinaryCostFunction::declareOptions(OptionList &ol)
{
    declareOption(ol, "make_positive_output", &LiftBinaryCostFunction::make_positive_output, OptionBase::buildoption,
                   "TODO: Some comments");
    inherited::declareOptions(ol);
}

} // end of namespace PLearn

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