db1a642cd2
The idea is to use ffmath.h for internal implementations of math functions. Currently, it is used for variants of libm functions, but is by no means limited to such things. Note that this is not exported; use lavu/mathematics for such purposes. Reviewedby: Ronald S. Bultje <rsbultje@gmail.com> Signedoffby: Ganesh Ajjanagadde <gajjanag@gmail.com>
68 lines
2.0 KiB
C
68 lines
2.0 KiB
C
/*


* 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 021101301 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


* ~ 1e13 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 */
