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// Copyright (C) 2002 Ronan Collobert (collober@iro.umontreal.ca)
//
//
// This file is part of Torch. Release II.
// [The Ultimate Machine Learning Library]
//
// Torch is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// Torch is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Torch; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
#include "LogSigmoid.h"
namespace Torch {
LogSigmoid::LogSigmoid(int n_units)
{
n_outputs = n_units;
buff = NULL;
}
int LogSigmoid::numberOfParams()
{
return(0);
}
void LogSigmoid::allocateMemory()
{
GradientMachine::allocateMemory();
buff = (real *)xalloc(sizeof(real)*n_outputs);
}
void LogSigmoid::freeMemory()
{
if(is_free)
return;
GradientMachine::freeMemory();
free(buff);
is_free = true;
}
void LogSigmoid::forward(List *inputs)
{
real *ptr_out = (real *)outputs->ptr;
real *ptr_buff = buff;
while(inputs)
{
real *x = (real *)inputs->ptr;
for(int j = 0; j < inputs->n; j++)
{
*ptr_buff = exp(- *x++);
*ptr_out++ = -log(1.+ *ptr_buff++);
}
inputs = inputs->next;
}
}
void LogSigmoid::backward(List *inputs, real *alpha)
{
real *alpha_ptr = alpha;
real *beta_ptr = beta;
real *buff_ptr = buff;
for(int i = 0; i < n_outputs; i++)
{
real z = *buff_ptr++;
*beta_ptr++ = *alpha_ptr++ * z / (1. + z);
}
}
LogSigmoid::~LogSigmoid()
{
freeMemory();
}
}
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