TimesConstantVariable.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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/* *******************************************************      
   * $Id: TimesConstantVariable.cc,v 1.7 2004/04/27 16:02:26 morinf Exp $
   * This file is part of the PLearn library.
   ******************************************************* */

#include "TimesConstantVariable.h"
#include "Var_operators.h"

namespace PLearn {
using namespace std;


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

TimesConstantVariable::TimesConstantVariable(Variable* input, real c)
  : inherited(input, input->length(), input->width()), cst(c) 
{}

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

void TimesConstantVariable::fprop()
{
  for(int k=0; k<nelems(); k++)
    valuedata[k] = input->valuedata[k] * cst;
}


void TimesConstantVariable::bprop()
{
  for(int k=0; k<nelems(); k++)
    input->gradientdata[k] += cst*gradientdata[k];
}


void TimesConstantVariable::symbolicBprop()
{
  input->accg(g*cst);
}


// R(cx) = cR(x)
void TimesConstantVariable::rfprop()
{
  if (rValue.length()==0) resizeRValue();
  for(int k=0; k<nelems(); k++)
    rvaluedata[k] = input->rvaluedata[k]*cst;
}



} // end of namespace PLearn

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