blob: aad1347f26d4110acccc36f498b8eace69e95f6c
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 "attributes.h" |
30 | #include "libm.h" |
31 | |
32 | /** |
33 | * Compute 10^x for floating point values. Note: this function is by no means |
34 | * "correctly rounded", and is meant as a fast, reasonably accurate approximation. |
35 | * For instance, maximum relative error for the double precision variant is |
36 | * ~ 1e-13 for very small and very large values. |
37 | * This is ~2x faster than GNU libm's approach, which is still off by 2ulp on |
38 | * some inputs. |
39 | * @param x exponent |
40 | * @return 10^x |
41 | */ |
42 | static av_always_inline double ff_exp10(double x) |
43 | { |
44 | return exp2(M_LOG2_10 * x); |
45 | } |
46 | |
47 | static av_always_inline float ff_exp10f(float x) |
48 | { |
49 | return exp2f(M_LOG2_10 * x); |
50 | } |
51 | |
52 | /** |
53 | * Compute x^y for floating point x, y. Note: this function is faster than the |
54 | * libm variant due to mainly 2 reasons: |
55 | * 1. It does not handle any edge cases. In particular, this is only guaranteed |
56 | * to work correctly for x > 0. |
57 | * 2. It is not as accurate as a standard nearly "correctly rounded" libm variant. |
58 | * @param x base |
59 | * @param y exponent |
60 | * @return x^y |
61 | */ |
62 | static av_always_inline float ff_fast_powf(float x, float y) |
63 | { |
64 | return expf(logf(x) * y); |
65 | } |
66 | |
67 | #endif /* AVUTIL_FFMATH_H */ |
68 |