ElementAtPositionVariable.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:
// 
//  1. Redistributions of source code must retain the above copyright
//     notice, this list of conditions and the following disclaimer.
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/* *******************************************************      
   * $Id: ElementAtPositionVariable.cc,v 1.5 2004/04/27 16:04:54 morinf Exp $
   * This file is part of the PLearn library.
   ******************************************************* */

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

namespace PLearn {
using namespace std;


PLEARN_IMPLEMENT_OBJECT(ElementAtPositionVariable,
                        "A variable of size length() x width(), filled with zeros except for the "
                        "single element indexed by input2 =(i,j) or input2 = (k).",
                        "NO HELP");

ElementAtPositionVariable::ElementAtPositionVariable(Variable* input1, Variable* input2, int the_length, int the_width)
  : inherited(input1, input2, the_length, the_width), length_(the_length), width_(the_width)
{
    build_();
}

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

void
ElementAtPositionVariable::build_()
{
  if (input1 && !input1->isScalar())
      PLERROR("In ElementAtPositionVariable: element must be a scalar var");
  if (input2 && input2->nelems()>2)
      PLERROR("In ElementAtPositionVariable: position must have 1 or 2 elements");
}

void
ElementAtPositionVariable::declareOptions(OptionList &ol)
{
    declareOption(ol, "length_", &ElementAtPositionVariable::length_, OptionBase::buildoption, "");
    declareOption(ol, "width_", &ElementAtPositionVariable::width_, OptionBase::buildoption, "");
    inherited::declareOptions(ol);
}

void ElementAtPositionVariable::recomputeSize(int& l, int& w) const
{ l=length_; w=width_; }

void ElementAtPositionVariable::fprop()
{
  value.clear();
  if (input2->isScalar()) // input2 is a scalar (interpreted as a k)
    {
      int k = (int)input2->valuedata[0];
      valuedata[k] = input1->valuedata[0];
    }
  else // input2 has 2 elements (interpreted as (i,j) coordinates)
    {
      int i = (int)input2->valuedata[0];
      int j = (int)input2->valuedata[1];
      valuedata[i*width()+j] = input1->valuedata[0];
    }
}


void ElementAtPositionVariable::bprop()
{
  if (input2->isScalar()) // input2 is a scalar (interpreted as a k)
    {
      int k = (int)input2->valuedata[0];
      input1->gradientdata[0] += gradientdata[k];
    }
  else // input2 has 2 elements (interpreted as (i,j) coordinates)
    {
      int i = (int)input2->valuedata[0];
      int j = (int)input2->valuedata[1];
      input1->gradientdata[0] += gradientdata[i*width()+j];
    }  
}


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



void ElementAtPositionVariable::rfprop()
{
  if (rValue.length()==0) resizeRValue();
  rValue.clear();
  if (input2->isScalar()) // input2 is a scalar (interpreted as a k)
    {
      int k = (int)input2->valuedata[0];
      rvaluedata[k] = input1->rvaluedata[0];
    }
  else // input2 has 2 elements (interpreted as (i,j) coordinates)
    {
      int i = (int)input2->valuedata[0];
      int j = (int)input2->valuedata[1];
      rvaluedata[i*width()+j] = input1->rvaluedata[0];
    }
}



} // end of namespace PLearn

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