math_utils.hpp
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// This file is part of OpenCV project.
// It is subject to the license terms in the LICENSE file found in the top-level directory
// of this distribution and at http://opencv.org/license.html.
// Code is borrowed from https://github.com/kaldi-asr/kaldi/blob/master/src/base/kaldi-math.h
// base/kaldi-math.h
// Copyright 2009-2011 Ondrej Glembek; Microsoft Corporation; Yanmin Qian;
// Jan Silovsky; Saarland University
//
// See ../../COPYING for clarification regarding multiple authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
// WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
// MERCHANTABLITY OR NON-INFRINGEMENT.
// See the Apache 2 License for the specific language governing permissions and
// limitations under the License.
#ifndef __OPENCV_DNN_MATH_UTILS_HPP__
#define __OPENCV_DNN_MATH_UTILS_HPP__
#ifdef OS_QNX
#include <math.h>
#else
#include <cmath>
#endif
#include <limits>
#ifndef FLT_EPSILON
#define FLT_EPSILON 1.19209290e-7f
#endif
namespace cv { namespace dnn {
const float kNegativeInfinity = -std::numeric_limits<float>::infinity();
const float kMinLogDiffFloat = std::log(FLT_EPSILON);
#if !defined(_MSC_VER) || (_MSC_VER >= 1700)
inline float Log1p(float x) { return log1pf(x); }
#else
inline float Log1p(float x) {
const float cutoff = 1.0e-07;
if (x < cutoff)
return x - 2 * x * x;
else
return Log(1.0 + x);
}
#endif
inline float Exp(float x) { return expf(x); }
inline float LogAdd(float x, float y) {
float diff;
if (x < y) {
diff = x - y;
x = y;
} else {
diff = y - x;
}
// diff is negative. x is now the larger one.
if (diff >= kMinLogDiffFloat) {
float res;
res = x + Log1p(Exp(diff));
return res;
} else {
return x; // return the larger one.
}
}
}} // namespace
#endif // __OPENCV_DNN_MATH_UTILS_HPP__