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Benchmarks

The results below can only give a rough estimate of the resources necessary for using certain library functions. There is a number of factors which can both increase or reduce the effort required:

• Expenses for preparation of operands and their stack are not considered.

• In the table, the size includes all additional functions (for example, function to multiply two integers) but they are only linked from the library.

• Expenses of time of performance of some functions essentially depend on parameters of a call, for example, qsort() is recursive, and sprintf() receives parameters in a stack.

• Different versions of the compiler can give a significant difference in code size and execution time. For example, the float version of sscanf() function, compiled with avr-gcc 3.4.6, requires 3792 bytes and uses 124 bytes of stack. After transition to avr-gcc 4.2.2, the size become 3886 bytes, using 140 bytes of stack.

A few of libc functions.

Avr-gcc version is 4.2.2

Function	Units	Avr2	Avr25	Avr4
atoi ("12345")	Flash bytes Stack bytes MCU clocks	82 2 155	78	74 2 149
atol ("12345")	Flash bytes Stack bytes MCU clocks	122 2 221	118	118 2 219
dtostre (1.2345, s, 6, 0)	Flash bytes Stack bytes MCU clocks	1184 17 1313	1088	1088 17 1152
dtostrf (1.2345, 15, 6, s)	Flash bytes Stack bytes MCU clocks	1676 36 1608	1548	1548 36 1443
itoa (12345, s, 10)	Flash bytes Stack bytes MCU clocks	150 4 1172	134	134 4 1152
ltoa (12345L, s, 10)	Flash bytes Stack bytes MCU clocks	220 9 3174	200	200 9 3136
malloc (1)	Flash bytes Stack bytes MCU clocks	556 4 197	508	508 4 179
realloc ((void *)0, 1)	Flash bytes Stack bytes MCU clocks	1156 20 304	1046	1046 20 281
qsort (s, sizeof(s), 1, cmp)	Flash bytes Stack bytes MCU clocks	1242 38 20914	990	1008 38 16678
sprintf_min (s, "%d", 12345)	Flash bytes Stack bytes MCU clocks	1216 59 1846	1090	1086 59 1711
sprintf (s, "%d", 12345)	Flash bytes Stack bytes MCU clocks	1674 58 1610	1542	1498 58 1528
sprintf_flt (s, "%e", 1.2345)	Flash bytes Stack bytes MCU clocks	3334 66 2513	3084	3040 66 2297
sscanf_min ("12345", "%d", &i)	Flash bytes Stack bytes MCU clocks	1528 60 1743	1378	1390 60 1456
sscanf ("12345", "%d", &i)	Flash bytes Stack bytes MCU clocks	1880 62 1849	1724	1694 62 1561
sscanf_flt ("1.2345", "%e", &x)	Flash bytes Stack bytes MCU clocks	4250 140 3131	3916	3886 140 2756
strtod ("1.2345", &p)	Flash bytes Stack bytes MCU clocks	1638 22 1273	1550	1514 22 1012
strtol ("12345", &p, 0)	Flash bytes Stack bytes MCU clocks	956 29 1081	888	822 21 729

Math functions.

The table contains the number of MCU clocks to calculate a function with a given argument(s). The main reason of a big difference between Avr2 and Avr4 is a hardware multiplication.

Function	Avr2	Avr4
__addsf3 (1.234, 5.678)	113	108
__mulsf3 (1.234, 5.678)	375	138
__divsf3 (1.234, 5.678)	466	465
acos (0.54321)	4648	2689
asin (0.54321)	4754	2790
atan (0.54321)	4710	2271
atan2 (1.234, 5.678)	5270	2857
ceil (1.2345)	177	177
cos (1.2345)	3381	1665
cosh (1.2345)	4922	2979
exp (1.2345)	4708	2765
fdim (5.678, 1.234)	111	111
floor (1.2345)	180	180
fmax (1.234, 5.678)	39	37
fmin (1.234, 5.678)	35	35
fmod (5.678, 1.234)	132	132
frexp (1.2345, 0)	37	36
hypot (1.234, 5.678)	1556	1078
ldexp (1.2345, 6)	42	42
log (1.2345)	4142	2134
log10 (1.2345)	4498	2260
modf (1.2345, 0)	433	429
pow (1.234, 5.678)	9293	5047
round (1.2345)	150	150
sin (1.2345)	3347	1647
sinh (1.2345)	4946	3003
sqrt (1.2345)	709	704
tan (1.2345)	4375	2420
tanh (1.2345)	5126	3173
trunc (1.2345)	178	178

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