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

#include "VarRowsVariable.h"

namespace PLearn {
using namespace std;


PLEARN_IMPLEMENT_OBJECT(VarRowsVariable,
                        "Variable that is a subset of a matrix's rows; "
                        "input1 : matrix from which rows are selected; "
                        "input2 : vector whose elements are row indices in input1",
                        "NO HELP");

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

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

void
VarRowsVariable::build_()
{
    if (input1)
        input1->allowPartialUpdates();
}

void VarRowsVariable::recomputeSize(int& l, int& w) const
{
    if (input1 && input2) {
        l = input2->length();
        w = input1->width();
    } else
        l = w = 0;
}

void VarRowsVariable::fprop()
{
  matValue << input1->matValue.rows(input2->value);
}


void VarRowsVariable::bprop()
{
  for (int i = 0; i < input2->length(); ++i)
  {
    int r=int(input2->value[i]);
    input1->matGradient.row(r) += matGradient.row(i);
    input1->updateRow(r);
  }
}


void VarRowsVariable::symbolicBprop()
{
  PLERROR("VarRowsVariable::symbolicBprop() not implemented");
}



} // end of namespace PLearn

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