ColumnIndexVariable.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: ColumnIndexVariable.cc,v 1.5 2004/04/27 15:58:16 morinf Exp $
   * This file is part of the PLearn library.
   ******************************************************* */

#include "ColumnIndexVariable.h"
#include "IndexAtPositionVariable.h"
namespace PLearn {
using namespace std;



PLEARN_IMPLEMENT_OBJECT(ColumnIndexVariable,
                        "Return a row vector with the elements indexed in each column",
                        "NO HELP");

ColumnIndexVariable::ColumnIndexVariable(Variable *input1, Variable *input2)
  : inherited(input1, input2, 1/*input2->length()*/, input1->width())
{
    build_();
}

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

void
ColumnIndexVariable::build_()
{
    if (input2 && !input2->isVec())
        PLERROR("In ColumnIndexVariable: input2 must be a vector variable representing the indexs of input1");
}

void ColumnIndexVariable::recomputeSize(int& l, int& w) const
{
    l = 1; /*input2->length()*/
    if (input1)
        w = input1->width();
    else
        w = 0;
}

void ColumnIndexVariable::fprop()
{
  for (int i=0; i<input2->size(); i++)
    {
    int num = (int)input2->valuedata[i];
    valuedata[i] = input1->valuedata[num*input1->width()+i];
    }
}


void ColumnIndexVariable::bprop()
{
  for (int i=0; i<input2->size(); i++)
    {
    int num = (int) input2->valuedata[i];
    input1->gradientdata[num*input1->width()+i] += gradientdata[i];
    }
}


void ColumnIndexVariable::symbolicBprop()
{
  input1->accg(new IndexAtPositionVariable(g,input2,input1->length(),input1->width()));
}



} // end of namespace PLearn

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