Libfixmath

{{Infobox software

| name = libfixmath

| developer = Ben Brewer

| latest_release_version = r64

| latest_release_date = {{Start date and age|2012|02|02}}

| programming language = C99

| operating_system = Cross-platform

| genre = fixed-point math library

| license = MIT

| website =

}}

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).{{cite web|url=https://github.com/PetteriAimonen/libfixmath|title=libfixmath Project Page|website=GitHub }}

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.{{cite web|url=https://code.google.com/p/libfixmath/issues/detail?id=4|title=64-bit Compiler Support Issues}}

History

libfixmath was developed by Ben Brewer and first released publicly as part of the Dingoo SDK.{{cite web|url=https://code.google.com/p/dingoo-sdk|title=Dingoo SDK Project Page}} It has since been used to implement a software 3D graphics library called FGL.{{cite web|url=https://code.google.com/p/fgl|title=FGL Flatmush/Fixed-Point Graphics Library Project Page}}

Q16.16 functions

Name	Description
class="wikitable"
`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
class="wikitable"
`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
class="wikitable"
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.{{cite web|url=https://code.google.com/p/libfixmath/downloads/detail?name=fixtest_r16.zip|title=fixtest Download Page}}