TimesScalarVariable.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: TimesScalarVariable.cc,v 1.6 2004/04/27 15:58:16 morinf Exp $
   * This file is part of the PLearn library.
   ******************************************************* */

#include "DotProductVariable.h"
#include "TimesScalarVariable.h"
#include "Var_operators.h"


namespace PLearn {
using namespace std;

PLEARN_IMPLEMENT_OBJECT(TimesScalarVariable,
                        "Multiplies a matrix var by a scalar var",
                        "NO HELP");

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

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

void
TimesScalarVariable::build_()
{
    if (input2 && !input2->isScalar())
        PLERROR("IN TimesScalarVariable: input2 is not a scalar");
}

void TimesScalarVariable::recomputeSize(int& l, int& w) const
{
    if (input1) {
        l = input1->length();
        w = input1->width();
    } else
        l = w = 0;
}

void TimesScalarVariable::fprop()
{
  real scal = input2->valuedata[0];
  for(int k=0; k<nelems(); k++)
    valuedata[k] = input1->valuedata[k] * scal;
}


void TimesScalarVariable::bprop()
{
  for(int k=0; k<nelems(); k++)
    {
      input1->gradientdata[k] += input2->valuedata[0]*gradientdata[k];
      input2->gradientdata[0] += input1->valuedata[k]*gradientdata[k];
    }
}


void TimesScalarVariable::symbolicBprop()
{
  input1->accg(g*input2);
  input2->accg(dot(g,input1));
}


//R(x1x2)=R(x1)x2+x1R(x2)
void TimesScalarVariable::rfprop()
{
  if (rValue.length()==0) resizeRValue();
  real scal = input2->valuedata[0];
  real rscal = input2->rvaluedata[0];
  for(int k=0; k<nelems(); k++)
    rvaluedata[k] = input1->rvaluedata[k] * scal + input1->valuedata[k] * rscal;
}



} // end of namespace PLearn

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