SoftmaxVariable.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

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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: SoftmaxVariable.h,v 1.5 2004/04/27 16:02:26 morinf Exp $
   * This file is part of the PLearn library.
   ******************************************************* */

#ifndef SoftmaxVariable_INC
#define SoftmaxVariable_INC

#include "UnaryVariable.h"
#include "MatrixSoftmaxVariable.h"

namespace PLearn {
using namespace std;


class SoftmaxVariable: public UnaryVariable
{
  typedef UnaryVariable inherited;

public:
  SoftmaxVariable() {}
  SoftmaxVariable(Variable* input);

  PLEARN_DECLARE_OBJECT(SoftmaxVariable);

  virtual void recomputeSize(int& l, int& w) const;
  virtual void fprop();
  virtual void bprop();
  virtual void bbprop();
  virtual void symbolicBprop();
  virtual void rfprop();
};

DECLARE_OBJECT_PTR(SoftmaxVariable);

// Now we have a special box!
inline Var softmax(Var v)
{
 if(v->isVec()) 
   return new SoftmaxVariable(v);
 else return new MatrixSoftmaxVariable(v);
}

//* OLD implementation 
/*
inline Var old_softmax(Var input)
{ 
  Var maxin = max(input);
  Var exp_input = exp(input-maxin);
  return exp_input/sum(exp_input); 
}
*/


} // end of namespace PLearn

#endif 

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