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

#include "ArgminVariable.h"

namespace PLearn {
using namespace std;


PLEARN_IMPLEMENT_OBJECT(ArgminVariable,
                        "Compute the index of the minimum value in the input",
                        "NO HELP");

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

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

void ArgminVariable::fprop()
{
  real minval = input->valuedata[0];
  if (input->isVec())
    {
      int argmin = 0;
      for(int i=1; i<input->nelems(); i++)
        {
          real val = input->valuedata[i];
          if(val<minval)
            {
              minval = val;
              argmin = i;
            }
        }
      valuedata[0] = argmin;
    }
  else
    {
      int k = 0;
      int argmin_i = 0;
      int argmin_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<minval)
              {
                minval = val;
                argmin_i = i;
                argmin_j = j;
              }
          }
      valuedata[0] = argmin_i;
      valuedata[1] = argmin_j;
    }
}


void ArgminVariable::bprop() {}

void ArgminVariable::symbolicBprop() {}



} // end of namespace PLearn

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