/src/ffmpeg/libavutil/ffmath.h
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1 | | /* |
2 | | * copyright (c) 2016 Ganesh Ajjanagadde <gajjanag@gmail.com> |
3 | | * |
4 | | * This file is part of FFmpeg. |
5 | | * |
6 | | * FFmpeg is free software; you can redistribute it and/or |
7 | | * modify it under the terms of the GNU Lesser General Public |
8 | | * License as published by the Free Software Foundation; either |
9 | | * version 2.1 of the License, or (at your option) any later version. |
10 | | * |
11 | | * FFmpeg is distributed in the hope that it will be useful, |
12 | | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
13 | | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
14 | | * Lesser General Public License for more details. |
15 | | * |
16 | | * You should have received a copy of the GNU Lesser General Public |
17 | | * License along with FFmpeg; if not, write to the Free Software |
18 | | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
19 | | */ |
20 | | |
21 | | /** |
22 | | * @file |
23 | | * internal math functions header |
24 | | */ |
25 | | |
26 | | #ifndef AVUTIL_FFMATH_H |
27 | | #define AVUTIL_FFMATH_H |
28 | | |
29 | | #include <math.h> |
30 | | |
31 | | #include "attributes.h" |
32 | | #include "mathematics.h" |
33 | | |
34 | | /** |
35 | | * Compute 10^x for floating point values. Note: this function is by no means |
36 | | * "correctly rounded", and is meant as a fast, reasonably accurate approximation. |
37 | | * For instance, maximum relative error for the double precision variant is |
38 | | * ~ 1e-13 for very small and very large values. |
39 | | * This is ~2x faster than GNU libm's approach, which is still off by 2ulp on |
40 | | * some inputs. |
41 | | * @param x exponent |
42 | | * @return 10^x |
43 | | */ |
44 | | static av_always_inline double ff_exp10(double x) |
45 | 0 | { |
46 | 0 | return exp2(M_LOG2_10 * x); |
47 | 0 | } |
48 | | |
49 | | static av_always_inline float ff_exp10f(float x) |
50 | 0 | { |
51 | 0 | return exp2f(M_LOG2_10 * x); |
52 | 0 | } |
53 | | |
54 | | /** |
55 | | * Compute x^y for floating point x, y. Note: this function is faster than the |
56 | | * libm variant due to mainly 2 reasons: |
57 | | * 1. It does not handle any edge cases. In particular, this is only guaranteed |
58 | | * to work correctly for x > 0. |
59 | | * 2. It is not as accurate as a standard nearly "correctly rounded" libm variant. |
60 | | * @param x base |
61 | | * @param y exponent |
62 | | * @return x^y |
63 | | */ |
64 | | static av_always_inline float ff_fast_powf(float x, float y) |
65 | 0 | { |
66 | 0 | return expf(logf(x) * y); |
67 | 0 | } |
68 | | |
69 | | #endif /* AVUTIL_FFMATH_H */ |