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.
History
libfixmath was developed by Ben Brewer and first released publicly as part of the Dingoo SDK.3 It has since been used to implement a software 3D graphics library called FGL.4
Q16.16 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 |
Other functions
| Name | Description |
|---|---|
| fix16_to_dbl | Convert Q16.16 to a double |
| fix16_to_float | Convert Q16.16 to a float |
| fix16_to_int | Convert Q16.16 to an integer |
| fix16_from_dbl | Convert double to a Q16.16 |
| fix16_from_float | Convert float to a Q16.16 |
| fix16_from_int | Convert integer to a Q16.16 |
Performance
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.5
Licensing
libfixmath is released under the MIT License, a permissive free software licence, and is free software.
See also
- Free Software portal
External links
References
"libfixmath Project Page". GitHub. https://github.com/PetteriAimonen/libfixmath ↩
"64-bit Compiler Support Issues". https://code.google.com/p/libfixmath/issues/detail?id=4 ↩
"Dingoo SDK Project Page". https://code.google.com/p/dingoo-sdk ↩
"FGL Flatmush/Fixed-Point Graphics Library Project Page". https://code.google.com/p/fgl ↩
"fixtest Download Page". https://code.google.com/p/libfixmath/downloads/detail?name=fixtest_r16.zip ↩