Libfixmath
Platform-independent fixed-point math library
libfixmath is a platform-independent fixed-point math library aimed at developers wanting to perform fast non-integer math on platforms lacking a (or with a low performance) FPU. It offers developers a similar interface to the standard math.h functions for use on Q16.16 fixed-point numbers. libfixmath has no external dependencies other than stdint.h and a compiler which supports 64-bit integer arithmetic (such as GCC). Conditional compilation options exist to remove the requirement for a 64-bit capable compiler as many compilers for microcontrollers and DSPs do not support 64-bit arithmetic.
01History
libfixmath was developed by Ben Brewer and first released publicly as part of the Dingoo SDK. It has since been used to implement a software 3D graphics library called FGL.
02Q16.16 functions
| Name | Description |
|---|---|
| fix16_acos | inverse cosine |
| fix16_asin | inverse sine |
| fix16_atan | one-parameter inverse tangent |
| fix16_atan2 | two-parameter inverse tangent |
| fix16_cos | cosine |
| fix16_exp | exponential function |
| fix16_sin | sine |
| fix16_sqrt | square root |
| fix16_tan | tangent |
| fix16_mul | multiplication |
| fix16_div | division |
| fix16_sadd | saturated addition |
| fix16_smul | saturated multiplication |
| fix16_sdiv | saturated division |
03Other functions
04Performance
For the most intensive function (atan2) benchmark results show the following results:
| Name | Time Compared to Float |
|---|---|
| ARM Cortex-M0 | 26.3% |
| Marvell PXA270 (ARM) @ 312 MHz | 58.45% |
| Intel T5500 | 120% |
| Intel Atom N280 | 141% |
Note: These results were calculated using fixtest with caching optimizations turned off.
05Licensing
libfixmath is released under the MIT License, a permissive free software licence, and is free software.
Sources and credits
This article is adapted from the Wikipedia article “Libfixmath”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
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