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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 "Softmax.h"
namespace Torch {
Softmax::Softmax(int n_units)
{
n_inputs = n_units;
n_outputs = n_units;
addROption("shift", &shift, 0, "shift to avoid overflow", true);
addBOption("compute shift", &calc_shift, false, "compute shift to avoid overflow", true);
}
int Softmax::numberOfParams()
{
return(0);
}
void Softmax::forward(List *inputs)
{
if(calc_shift)
{
List *inputs_ = inputs;
shift = ((real *)inputs_->ptr)[0];
while(inputs_)
{
real *x = (real *)inputs_->ptr;
for(int j = 0; j < inputs_->n; j++, x++)
{
if(*x > shift)
shift = *x;
}
inputs_ = inputs_->next;
}
}
real *ptr_out = (real *)outputs->ptr;
real sum = 0;
while(inputs)
{
real *x = (real *)inputs->ptr;
for(int j = 0; j < inputs->n; j++)
{
real z = exp(*x++ - shift);
*ptr_out++ = z;
sum += z;
}
inputs = inputs->next;
}
ptr_out = (real *)outputs->ptr;
for(int i = 0; i < n_outputs; i++)
*ptr_out++ /= sum;
}
void Softmax::backward(List *inputs, real *alpha)
{
real *ptr_alpha = alpha;
real *ptr_outputs = (real *)outputs->ptr;
real sum = 0;
for(int i = 0; i < n_outputs; i++)
sum += *ptr_alpha++ * *ptr_outputs++;
ptr_alpha = alpha;
ptr_outputs = (real *)outputs->ptr;
real *ptr_beta = beta;
for(int i = 0; i < n_outputs; i++)
*ptr_beta++ = *ptr_outputs++ * (*ptr_alpha++ - sum);
}
Softmax::~Softmax()
{
}
}
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