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// Copyright (C) 2003--2004 Samy Bengio (bengio@idiap.ch)
//
// This file is part of Torch 3.1.
//
// All rights reserved.
//
// 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.
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
// 3. The name of the author may not be used to endorse or promote products
// derived from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
// IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
// OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
// IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
// NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
// THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "log_add.h"
#include "general.h"
namespace Torch {
#ifdef USE_DOUBLE
#define MINUS_LOG_THRESHOLD -39.14
#else
#define MINUS_LOG_THRESHOLD -18.42
#endif
real logAdd(real log_a, real log_b)
{
if (log_a < log_b) {
real tmp = log_a;
log_a = log_b;
log_b = tmp;
}
real minusdif = log_b - log_a;
#ifdef DEBUG
if (isnan(minusdif))
error("LogAdd: minusdif (%f) log_b (%f) or log_a (%f) is nan",minusdif,log_b,log_a);
#endif
if (minusdif < MINUS_LOG_THRESHOLD)
return log_a;
else
return log_a + log1p(exp(minusdif));
}
real logSub(real log_a, real log_b)
{
if (log_a < log_b)
error("LogSub: log_a (%f) should be greater than log_b (%f)", log_a, log_b);
real minusdif = log_b - log_a;
#ifdef DEBUG
if (isnan(minusdif))
error("LogSub: minusdif (%f) log_b (%f) or log_a (%f) is nan",minusdif,log_b,log_a);
#endif
if (log_a == log_b)
return LOG_ZERO;
else if (minusdif < MINUS_LOG_THRESHOLD)
return log_a;
else
return log_a + log1p(-exp(minusdif));
}
}
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