LogSumVariable.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: LogSumVariable.cc,v 1.5 2004/02/20 21:11:50 chrish42 Exp $
   * This file is part of the PLearn library.
   ******************************************************* */

#include "LogSumVariable.h"
#include "SoftmaxVariable.h"
#include "Var_operators.h"
//#include "Var_utils.h"

namespace PLearn {
using namespace std;



LogSumVariable::LogSumVariable(Variable* input)
  :UnaryVariable(input,1,1),input_softmax(input->nelems()) {}


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

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








void LogSumVariable::makeDeepCopyFromShallowCopy(map<const void*, void*>& copies)
{
  UnaryVariable::makeDeepCopyFromShallowCopy(copies);
  deepCopyField(input_softmax, copies);
}


void LogSumVariable::fprop()
{
  valuedata[0] = logadd(input->value);
}


void LogSumVariable::bprop()
{
  softmax(input->value,input_softmax);
  multiplyAcc(input->gradient, input_softmax,gradientdata[0]);
}


void LogSumVariable::symbolicBprop()
{
  input->accg(g*softmax(input));
}



} // end of namespace PLearn

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