MaxVariable.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

// 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
//     notice, this list of conditions and the following disclaimer.
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/* *******************************************************      
   * $Id: MaxVariable.cc,v 1.6 2004/04/27 16:02:26 morinf Exp $
   * This file is part of the PLearn library.
   ******************************************************* */

#include "ArgmaxVariable.h"
#include "ElementAtPositionVariable.h"
#include "MaxVariable.h"

namespace PLearn {
using namespace std;


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

MaxVariable::MaxVariable(Variable* input)
  : inherited(input, 1, 1)
{}

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

void MaxVariable::fprop()
{
  real maxval = input->valuedata[0];
  for(int i=1; i<input->nelems(); i++)
    {
      real val = input->valuedata[i];
      if(val>maxval)
        maxval = val;
    }
  valuedata[0] = maxval;
}


void MaxVariable::bprop()
{
  real maxval = valuedata[0];
  for(int i=0; i<input->nelems(); i++)
    {
      if(input->valuedata[i]==maxval)
        input->gradientdata[i] += gradientdata[0];
    }
}


void MaxVariable::symbolicBprop()
{
  input->accg(new ElementAtPositionVariable(g, argmax(input), input->length(), input->width()));
}

} // end of namespace PLearn

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