libfixmath

libfixmath is a platform-independent fixed point maths library aimed at developers wanting to perform fast non-integer maths 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).[1] 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.[2]

libfixmath
Developer(s)Ben Brewer (aka flatmush)
Stable release
r64 / February 2, 2012 (2012-02-02)
Repository
Written inC99
Operating systemCross-platform
Typefixed point math library
LicenseMIT
Websitehttps://github.com/PetteriAimonen/libfixmath

History

libfixmath was originally developed by Ben Brewer (aka flatmush) 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
NameDescription
fix16_acosinverse cosine
fix16_asininverse sine
fix16_atanone-parameter inverse tangent
fix16_atan2two-parameter inverse tangent
fix16_coscosine
fix16_expexponential function
fix16_sinsine
fix16_sqrtsquare root
fix16_tantangent
fix16_mulmultiplication
fix16_divdivision
fix16_saddsaturated addition
fix16_smulsaturated multiplication
fix16_sdivsaturated division

Other Functions
NameDescription
fix16_to_dblConvert Q16.16 to a double
fix16_to_floatConvert Q16.16 to a float
fix16_to_intConvert Q16.16 to an integer
fix16_from_dblConvert double to a Q16.16
fix16_from_floatConvert float to a Q16.16
fix16_from_intConvert integer to a Q16.16

Performance

For the most intensive function (atan2) benchmark results show the following results:

NameTime Compared to Float
ARM Cortex-M026.3%
Marvell PXA270 (ARM) @ 312 MHz58.45%
Intel T5500120%
Intel Atom N280141%

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

References
  1. "libfixmath Project Page".
  2. "64-bit Compiler Support Issues".
  3. "Dingoo SDK Project Page".
  4. "FGL Flatmush/Fixed-Point Graphics Library Project Page".
  5. "fixtest Download Page".
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