aac5773f
 hucm
功能基本完成，接口待打磨
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/*
* copyright (c) 2016 Ganesh Ajjanagadde <gajjanag@gmail.com>
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file
* internal math functions header
*/
#ifndef AVUTIL_FFMATH_H
#define AVUTIL_FFMATH_H
#include "attributes.h"
#include "libm.h"
/**
* Compute 10^x for floating point values. Note: this function is by no means
* "correctly rounded", and is meant as a fast, reasonably accurate approximation.
* For instance, maximum relative error for the double precision variant is
* ~ 1e-13 for very small and very large values.
* This is ~2x faster than GNU libm's approach, which is still off by 2ulp on
* some inputs.
* @param x exponent
* @return 10^x
*/
static av_always_inline double ff_exp10(double x)
{
return exp2(M_LOG2_10 * x);
}
static av_always_inline float ff_exp10f(float x)
{
return exp2f(M_LOG2_10 * x);
}
/**
* Compute x^y for floating point x, y. Note: this function is faster than the
* libm variant due to mainly 2 reasons:
* 1. It does not handle any edge cases. In particular, this is only guaranteed
* to work correctly for x > 0.
* 2. It is not as accurate as a standard nearly "correctly rounded" libm variant.
* @param x base
* @param y exponent
* @return x^y
*/
static av_always_inline float ff_fast_powf(float x, float y)
{
return expf(logf(x) * y);
}
#endif /* AVUTIL_FFMATH_H */
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