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

#include "VarElementVariable.h"
#include "ElementAtPositionVariable.h"

namespace PLearn {
using namespace std;


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

VarElementVariable::VarElementVariable(Variable* input1, Variable* input2)
  : inherited(input1, input2, 1, 1)
{
    build_();
}

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

void
VarElementVariable::build_()
{
    if (input2 && input2->nelems() > 2)
        PLERROR("IN VarElementVariable(Variable* input1, Variable* input2) input2 must have 1 (a k position index) or 2 elements (an i,j position index)");
}

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

void VarElementVariable::fprop()
{
  if(input2->isScalar()) // scalar position index k
    {
      int k = int(input2->valuedata[0]);
#ifdef BOUNDCHECK
      if (k >= input1->length())
          PLERROR("VarElementVariable::fprop() - k = %d is out of range (size is %d)", k, input1->length());
#endif
      valuedata[0] = input1->valuedata[k];
    }
  else // (i,j) position index
    {
      int i = int(input2->valuedata[0]);
      int j = int(input2->valuedata[1]);
#ifdef BOUNDCHECK
      if ((i * input1->width() + j) >= input1->width() * input1->length())
          PLERROR("VarElementVariable::fprop() - (%d, %d) out of range"
                  "(size is %d)", i, j, input1->length() * input1->width());
#endif
      valuedata[0] = input1->valuedata[i*input1->width()+j];
    }
}


void VarElementVariable::bprop()
{
  if(input2->isScalar()) // scalar position index k
    {
      int k = int(input2->valuedata[0]);
      input1->gradientdata[k] += gradientdata[0];
    }
  else // (i,j) position index
    {
      int i = int(input2->valuedata[0]);
      int j = int(input2->valuedata[1]);
      input1->gradientdata[i*input1->width()+j] += gradientdata[0];
    }
}


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


void VarElementVariable::rfprop()
{
  if (rValue.length()==0) resizeRValue();
  if(input2->isScalar()) // scalar position index k
    {
      int k = int(input2->valuedata[0]);
      rvaluedata[0] = input1->rvaluedata[k];
    }
  else // (i,j) position index
    {
      int i = int(input2->valuedata[0]);
      int j = int(input2->valuedata[1]);
      rvaluedata[0] = input1->rvaluedata[i*input1->width()+j];
    }
}



} // end of namespace PLearn

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