EqualVariable.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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// 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: EqualVariable.cc,v 1.6 2004/04/27 15:58:16 morinf Exp $
   * This file is part of the PLearn library.
   ******************************************************* */

#include "EqualVariable.h"
#include "EqualScalarVariable.h"

namespace PLearn {
using namespace std;




PLEARN_IMPLEMENT_OBJECT(EqualVariable,
                        "A scalar var;  equal 1 if input1==input2, 0 otherwise",
                        "NO HELP");

EqualVariable::EqualVariable(Variable* input1, Variable* input2)
  : inherited(input1, input2, 1,1)
{
    build_();
}

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

void
EqualVariable::build_()
{
    if (input1 && input2) {
        if (input1->length() != input2->length() || input1->width() != input2->width())
            PLERROR("IN EqualVariable(Variable* input1, Variable* input2) input1 and input2 must have the same size");
    }
}

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

void EqualVariable::fprop()
{
  bool equal=true;
  for (int i=0; i<nelems(); i++)
    equal = equal && (input1->valuedata[i] == input2->valuedata[i]);
  valuedata[0]=equal;
}


// not really differentiable (zero gradient almost everywhere)
void EqualVariable::bprop() {}

void EqualVariable::symbolicBprop() {}

Var isequal(Var v1, Var v2)
{
  if(v2->isScalar())
    return new EqualScalarVariable(v1,v2);
  else if(v1->isScalar())
    return new EqualScalarVariable(v2,v1);
  else
    return new EqualVariable(v1,v2);
}


} // end of namespace PLearn

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