| /* | |
| * copyright (c) 2016 Ganesh Ajjanagadde <[email protected]> | |
| * | |
| * 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 | |
| */ | |
| /** | |
| * 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); | |
| } | |