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 dtostre() function, compiled with avr-gcc 3.4.6, requires 930 bytes. After transition to avr-gcc 4.2.3, the size become 1088 bytes.

A few of libc functions.

Avr-gcc version is 4.7.1

The size of function is given in view of all picked up functions. By default AVR-LibC is compiled with -mcall-prologues option. In brackets the size without taking into account modules of a prologue and an epilogue is resulted. Both of the size can coincide, if function does not cause a prologue/epilogue.

Function	Units	Avr2	Avr25	Avr4
atoi ("12345")	Flash bytes Stack bytes MCU clocks	82 (82) 2 155	78 (78) 2 149	74 (74) 2 149
atol ("12345")	Flash bytes Stack bytes MCU clocks	122 (122) 2 221	118 (118) 2 219	118 (118) 2 219
dtostre (1.2345, s, 6, 0)	Flash bytes Stack bytes MCU clocks	1116 (1004) 17 1247	1048 (938) 17 1105	1048 (938) 17 1105
dtostrf (1.2345, 15, 6, s)	Flash bytes Stack bytes MCU clocks	1616 (1616) 38 1634	1508 (1508) 38 1462	1508 (1508) 38 1462
itoa (12345, s, 10)	Flash bytes Stack bytes MCU clocks	110 (110) 2 879	102 (102) 2 875	102 (102) 2 875
ltoa (12345L, s, 10)	Flash bytes Stack bytes MCU clocks	134 (134) 2 1597	126 (126) 2 1593	126 (126) 2 1593
malloc (1)	Flash bytes Stack bytes MCU clocks	768 (712) 6 215	714 (660) 6 201	714 (660) 6 201
realloc ((void *)0, 1)	Flash bytes Stack bytes MCU clocks	1284 (1172) 18 305	1174 (1064) 18 286	1174 (1064) 18 286
qsort (s, sizeof(s), 1, cmp)	Flash bytes Stack bytes MCU clocks	1252 (1140) 42 21996	1022 (912) 42 19905	1028 (918) 42 17541
sprintf_min (s, "%d", 12345)	Flash bytes Stack bytes MCU clocks	1224 (1112) 53 1841	1092 (982) 53 1694	1088 (978) 53 1689
sprintf (s, "%d", 12345)	Flash bytes Stack bytes MCU clocks	1614 (1502) 58 1647	1476 (1366) 58 1552	1454 (1344) 58 1547
sprintf_flt (s, "%e", 1.2345)	Flash bytes Stack bytes MCU clocks	3228 (3116) 67 2573	2990 (2880) 67 2311	2968 (2858) 67 2311
sscanf_min ("12345", "%d", &i)	Flash bytes Stack bytes MCU clocks	1532 (1420) 55 1607	1328 (1218) 55 1446	1328 (1218) 55 1446
sscanf ("12345", "%d", &i)	Flash bytes Stack bytes MCU clocks	2008 (1896) 55 1610	1748 (1638) 55 1449	1748 (1638) 55 1449
sscanf ("point,color", "%[a-z]", s)	Flash bytes Stack bytes MCU clocks	2008 (1896) 86 3067	1748 (1638) 86 2806	1748 (1638) 86 2806
sscanf_flt ("1.2345", "%e", &x)	Flash bytes Stack bytes MCU clocks	3464 (3352) 71 2497	3086 (2976) 71 2281	3070 (2960) 71 2078
strtod ("1.2345", &p)	Flash bytes Stack bytes MCU clocks	1632 (1520) 20 1235	1536 (1426) 20 1177	1480 (1480) 21 1124
strtol ("12345", &p, 0)	Flash bytes Stack bytes MCU clocks	918 (806) 22 956	834 (724) 22 891	792 (792) 28 794

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)	4411	2455
asin (0.54321)	4517	2556
atan (0.54321)	4710	2271
atan2 (1.234, 5.678)	5270	2857
cbrt (1.2345)	2684	2555
ceil (1.2345)	177	177
cos (1.2345)	3387	1671
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)	131	131
frexp (1.2345, 0)	42	41
hypot (1.234, 5.678)	1341	866
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)	3353	1653
sinh (1.2345)	4946	3003
sqrt (1.2345)	494	492
tan (1.2345)	4381	2426
tanh (1.2345)	5126	3173
trunc (1.2345)	178	178