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

#include "ArgmaxVariable.h"

namespace PLearn {
using namespace std;


PLEARN_IMPLEMENT_OBJECT(ArgmaxVariable,
                        "Compute the index of the maximum value in the input",
                        "NO HELP");

ArgmaxVariable::ArgmaxVariable(Variable* input)
  : inherited(input, input->isVec()?1:2, 1)
{}


void ArgmaxVariable::recomputeSize(int& l, int& w) const
{
    if (input)
        l = input->isVec() ? 1 : 2;
    w = 1;
}

void ArgmaxVariable::fprop()
{
  real maxval = input->valuedata[0];
  if (input->isVec())
    {
      int argmax = 0;
      for(int i=1; i<input->nelems(); i++)
        {
          real val = input->valuedata[i];
          if(val>maxval)
            {
              maxval = val;
              argmax = i;
            }
        }
      valuedata[0] = argmax;
    }
  else
    {
      int k = 0;
      int argmax_i = 0;
      int argmax_j = 0;
      for(int i=0; i<input->length(); i++)
        for(int j=0; j<input->width(); j++, k++)
          {
            real val = input->valuedata[k];
            if(val>maxval)
              {
                maxval = val;
                argmax_i = i;
                argmax_j = j;
              }
          }
      valuedata[0] = argmax_i;
      valuedata[1] = argmax_j;
    }
}


void ArgmaxVariable::bprop() {}

void ArgmaxVariable::symbolicBprop() {}



} // end of namespace PLearn

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