1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
|
/*!
* \file
* \brief Logarithmic and exponenential functions - source file
* \author Tony Ottosson, Adam Piatyszek and Conrad Sanderson
*
* -------------------------------------------------------------------------
*
* Copyright (C) 1995-2008 (see AUTHORS file for a list of contributors)
*
* This file is part of IT++ - a C++ library of mathematical, signal
* processing, speech processing, and communications classes and functions.
*
* IT++ 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 3 of the License, or (at your option) any
* later version.
*
* IT++ 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 IT++. If not, see <http://www.gnu.org/licenses/>.
*
* -------------------------------------------------------------------------
*/
#include <itpp/base/math/log_exp.h>
#include <itpp/base/itcompat.h>
namespace itpp
{
// log-2 of the elements
vec log2(const vec &x) { return apply_function<double>(::log2, x); }
mat log2(const mat &x) { return apply_function<double>(::log2, x); }
// Safe substitute for <tt>log(exp(log_a) + exp(log_b))</tt>
double log_add(double log_a, double log_b)
{
if (log_a < log_b) {
double tmp = log_a;
log_a = log_b;
log_b = tmp;
}
double negdelta = log_b - log_a;
if ((negdelta < log_double_min) || std::isnan(negdelta))
return log_a;
else
return (log_a + log1p(std::exp(negdelta)));
}
}
|
