BinaryClassificationLossVariable.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
// Copyright (C) 2004 Olivier Delalleau

// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
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//  1. Redistributions of source code must retain the above copyright
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/* *******************************************************      
   * $Id: BinaryClassificationLossVariable.cc,v 1.3 2004/04/27 15:58:16 morinf Exp $
   * This file is part of the PLearn library.
   ******************************************************* */

#include "BinaryClassificationLossVariable.h"
namespace PLearn {
using namespace std;

PLEARN_IMPLEMENT_OBJECT(BinaryClassificationLossVariable,
                        "For one-dimensional output: class is 0 if output < 0.5, and 1 if >= 0.5.",
                        "NO HELP");

BinaryClassificationLossVariable::BinaryClassificationLossVariable(Variable* netout, Variable* classnum)
  : inherited(netout,classnum,1,1)
{
    build_();
}

void
BinaryClassificationLossVariable::build()
{
    inherited::build();
    build_();
}

void
BinaryClassificationLossVariable::build_()
{
    // input2 == classnum from constructor
    if (input2 && !input2->isScalar())
        PLERROR("In BinaryClassificationLossVariable: classnum must be a scalar variable representing an index of netout (typically a class number)");
}

void BinaryClassificationLossVariable::recomputeSize(int& l, int& w) const
{ l=1, w=1; }


void BinaryClassificationLossVariable::fprop()
{
  int classnum = int(input2->valuedata[0]);
  int outputclass;
  if (input1->valuedata[0] <= 0.5) {
    outputclass = 0;
  } else {
    outputclass = 1;
  }
  
  valuedata[0] = (outputclass == classnum ?0 :1);
}

} // end of namespace PLearn

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