68 lines
2 KiB
C
68 lines
2 KiB
C
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/*
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* copyright (c) 2016 Ganesh Ajjanagadde <gajjanag@gmail.com>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* internal math functions header
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*/
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#ifndef AVUTIL_FFMATH_H
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#define AVUTIL_FFMATH_H
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#include "attributes.h"
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#include "libm.h"
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/**
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* Compute 10^x for floating point values. Note: this function is by no means
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* "correctly rounded", and is meant as a fast, reasonably accurate approximation.
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* For instance, maximum relative error for the double precision variant is
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* ~ 1e-13 for very small and very large values.
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* This is ~2x faster than GNU libm's approach, which is still off by 2ulp on
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* some inputs.
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* @param x exponent
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* @return 10^x
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*/
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static av_always_inline double ff_exp10(double x)
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{
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return exp2(M_LOG2_10 * x);
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}
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static av_always_inline float ff_exp10f(float x)
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{
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return exp2f(M_LOG2_10 * x);
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}
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/**
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* Compute x^y for floating point x, y. Note: this function is faster than the
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* libm variant due to mainly 2 reasons:
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* 1. It does not handle any edge cases. In particular, this is only guaranteed
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* to work correctly for x > 0.
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* 2. It is not as accurate as a standard nearly "correctly rounded" libm variant.
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* @param x base
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* @param y exponent
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* @return x^y
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*/
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static av_always_inline float ff_fast_powf(float x, float y)
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{
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return expf(logf(x) * y);
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}
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#endif /* AVUTIL_FFMATH_H */
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