SumVariable.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: SumVariable.cc,v 1.5 2004/04/27 16:02:26 morinf Exp $
   * This file is part of the PLearn library.
   ******************************************************* */

#include "SumVariable.h"

namespace PLearn {
using namespace std;



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

SumVariable::SumVariable(Variable* input)
  : inherited(input, 1, 1)
{}

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

void SumVariable::fprop()
{
  real sum = 0.0;
  for(int k=0; k<input->nelems(); k++)
    sum += input->valuedata[k];
  valuedata[0] = sum;
}


void SumVariable::bprop()
{
  real grd = gradientdata[0];
  for(int k=0; k<input->nelems(); k++)
    input->gradientdata[k] += grd;
}


void SumVariable::symbolicBprop()
{
  input->accg(g);
}


// R(sum_i x_i) = sum_i R(x_i)
void SumVariable::rfprop()
{
  if (rValue.length()==0) resizeRValue();
  real sum = 0.0;
  for(int k=0; k<input->nelems(); k++)
    sum += input->rvaluedata[k];
  rvaluedata[0] = sum;
}



} // end of namespace PLearn

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