Fast math functions

This material has been superseded. Visit learn.bela.io for the maintained version.

When programming in C++ on Bela, you have access to a library of fast, approximated math function: math_neon. This is a library that aims at replacing the accurate math functions implemented by the libmath library with faster, optimized and less accurate functions.

In order to use it, you will have to add

# include <libraries/math_neon/math_neon.h>

at the top of your file and then you can invoke the functions by adding _neon at the end of the name of a regular math.h function, e.g.: sinf(float) becomes sinf_neon(float)

Being these functions approximate, they may not suit all purposes and it is up to you to verify that they are accurate for your specific case. A list of the supported functions and a summary benchmark is in the table below. "rate" is the relative improvement of the "fast" version compared to the one in libmath.

Function	Range	Number	ABS Max Err	REL Max Err(%)	RMS Err	Time	Rate
sinf	-3.14, 3.14	500000	0.00000000	0.00000000	0.00000000	262041	1.00
sinf_neon	-3.14, 3.14	500000	0.00000083	0.85972977	0.00000041	66440	3.94
cosf	-3.14, 3.14	500000	0.00000000	0.00000000	0.00000000	215722	1.00
cosf_neon	-3.14, 3.14	500000	0.00000083	0.67412275	0.00000042	77271	2.79
tanf	-0.79, 0.79	500000	0.00000000	0.00000000	0.00000000	250169	1.00
tanf_neon	-0.79, 0.79	500000	0.00000191	0.00036218	0.00000067	97411	2.57
asinf	-1.00, 1.00	500000	0.00000000	0.00000000	0.00000000	229272	1.00
asinf_neon	-1.00, 1.00	500000	0.00004661	0.00889725	nan	121673	1.88
acosf	-1.00, 1.00	500000	0.00000000	0.00000000	0.00000000	277243	1.00
acosf_neon	-1.00, 1.00	500000	0.00004673	0.00634698	nan	123174	2.25
atanf	-1.00, 1.00	500000	0.00000000	0.00000000	0.00000000	206506	1.00
atanf_neon	-1.00, 1.00	500000	0.00016665	0.02123393	0.00007395	89627	2.30
sinhf	-3.14, 3.14	500000	0.00000000	0.00000000	0.00000000	313378	1.00
sinhf_neon	-3.14, 3.14	500000	0.00000191	0.15247960	0.00000019	75931	4.13
coshf	-3.14, 3.14	500000	0.00000000	0.00000000	0.00000000	327628	1.00
coshf_neon	-3.14, 3.14	500000	0.00000191	0.00002146	0.00000017	75932	4.31
tanhf	-3.14, 3.14	500000	0.00000000	0.00000000	0.00000000	322052	1.00
tanhf_neon	-3.14, 3.14	500000	0.00000024	0.24726489	0.00000005	74937	4.30
expf	0.00, 10.00	500000	0.00000000	0.00000000	0.00000000	288120	1.00
expf_neon	0.00, 10.00	500000	0.00976562	0.00006549	0.00164461	51935	5.55
logf	1.00, 1000.00	500000	0.00000000	0.00000000	0.00000000	220097	1.00
logf_neon	1.00, 1000.00	500000	0.00000763	0.01027698	0.00000107	52387	4.20
log10f	1.00, 1000.00	500000	0.00000000	0.00000000	0.00000000	273479	1.00
log10f_neon	1.00, 1000.00	500000	0.00000334	0.00668141	0.00000048	52388	5.22
floorf	1.00, 1000.00	5000000	0.00000000	0.00000000	0.00000000	566063	1.00
floorf_neon	1.00, 1000.00	5000000	0.00000000	0.00000000	0.00000000	339748	1.67
ceilf	1.00, 1000.00	5000000	0.00000000	0.00000000	0.00000000	617084	1.00
ceilf_neon	1.00, 1000.00	5000000	0.00000000	0.00000000	0.00000000	339745	1.82
fabsf	1.00, 1000.00	5000000	0.00000000	0.00000000	0.00000000	332227	1.00
fabsf_neon	1.00, 1000.00	5000000	0.00000000	0.00000000	0.00000000	226497	1.47
sqrtf	1.00, 1000.00	500000	0.00000000	0.00000000	0.00000000	152492	1.00
sqrtf_neon	1.00, 1000.00	500000	0.00000763	0.00002913	0.00000160	53386	2.86
invsqrtf	1.00, 1000.00	500000	0.00000000	0.00000000	0.00000000	54986	1.00
invsqrtf_neon	1.00, 1000.00	500000	0.00000012	0.00002124	0.00000000	38418	1.43
atan2f	0.10, 10.00	10000	0.00000000	0.00000000	0.00000000	511718	1.00
atan2f_neon	0.10, 10.00	10000	0.00016665	0.02124334	0.00000000	203125	2.52
powf	1.00, 10.00	10000	0.00000000	0.00000000	0.00000000	1783204	1.00
powf_neon	1.00, 10.00	10000	136192.00000000	0.00587880	0.00000000	201172	8.86
fmodf	1.00, 10.00	10000	0.00000000	0.00000000	0.00000000	140625	1.00
fmodf_neon	1.00, 10.00	10000	9.97472000	0.08058017	0.00000000	148437	0.95