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 4.2.3

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
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 (1072)
17
1313 1088 (978)

1088 (978)
17
1152
dtostrf (1.2345, 15, 6, s) Flash bytes
Stack bytes
MCU clocks 1676 (1564)
36
1608 1548 (1438)

1548 (1438)
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 554
4
196 506

506
4
178
realloc ((void*)0,1) Flash bytes
Stack bytes
MCU clocks 1152 (1040)
20
303 1042 (932)

1042 (932)
20
280
qsort (s,sizeof(s),1,cmp) Flash bytes
Stack bytes
MCU clocks 1242 (1130)
38
20914 990 (880)

1008 (898)
38
16678
sprintf_min (s,"%d",12345) Flash bytes
Stack bytes
MCU clocks 1216 (1104)
59
1846 1090 (980)

1086 (976)
59
1711
sprintf (s,"%d",12345) Flash bytes
Stack bytes
MCU clocks 1674 (1562)
58
1610 1542 (1432)

1498 (1388)
58
1528
sprintf_flt (s,"%e",1.2345) Flash bytes
Stack bytes
MCU clocks 3334 (3222)
66
2513 3084 (2974)

3040 (2930)
66
2297
sscanf_min ("12345","%d",&i) Flash bytes
Stack bytes
MCU clocks 1540 (1428)
55
1339 1354 (1244)

1354 (1244)
55
1240
sscanf ("12345","%d",&i) Flash bytes
Stack bytes
MCU clocks 1950 (1838)
53
1334 1704 (1594)

1704 (1594)
53
1235
sscanf ("point,color","%[a-z]",s) Flash bytes
Stack bytes
MCU clocks 1950 (1838)
87
2878 1704 (1594)

1704 (1594)
87
2718
sscanf_flt ("1.2345","%e",&x) Flash bytes
Stack bytes
MCU clocks 3298 (3186)
63
2187 2934 (2824)

2918 (2808)
63
1833
strtod ("1.2345",&p) Flash bytes
Stack bytes
MCU clocks 1570 (1458)
22
1237 1472 (1362)

1456 (1346)
22
971
strtol ("12345",&p,0) Flash bytes
Stack bytes
MCU clocks 942 (830)
29
1074 874 (764)

808 (698)
21
722

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 (1072) 17 1313	1088 (978)	1088 (978) 17 1152
`dtostrf (1.2345, 15, 6, s)`	Flash bytes Stack bytes MCU clocks	1676 (1564) 36 1608	1548 (1438)	1548 (1438) 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	554 4 196	506	506 4 178
`realloc ((void*)0,1)`	Flash bytes Stack bytes MCU clocks	1152 (1040) 20 303	1042 (932)	1042 (932) 20 280
`qsort (s,sizeof(s),1,cmp)`	Flash bytes Stack bytes MCU clocks	1242 (1130) 38 20914	990 (880)	1008 (898) 38 16678
`sprintf_min (s,"%d",12345)`	Flash bytes Stack bytes MCU clocks	1216 (1104) 59 1846	1090 (980)	1086 (976) 59 1711
`sprintf (s,"%d",12345)`	Flash bytes Stack bytes MCU clocks	1674 (1562) 58 1610	1542 (1432)	1498 (1388) 58 1528
`sprintf_flt (s,"%e",1.2345)`	Flash bytes Stack bytes MCU clocks	3334 (3222) 66 2513	3084 (2974)	3040 (2930) 66 2297
`sscanf_min ("12345","%d",&i)`	Flash bytes Stack bytes MCU clocks	1540 (1428) 55 1339	1354 (1244)	1354 (1244) 55 1240
`sscanf ("12345","%d",&i)`	Flash bytes Stack bytes MCU clocks	1950 (1838) 53 1334	1704 (1594)	1704 (1594) 53 1235
`sscanf ("point,color","%[a-z]",s)`	Flash bytes Stack bytes MCU clocks	1950 (1838) 87 2878	1704 (1594)	1704 (1594) 87 2718
`sscanf_flt ("1.2345","%e",&x)`	Flash bytes Stack bytes MCU clocks	3298 (3186) 63 2187	2934 (2824)	2918 (2808) 63 1833
`strtod ("1.2345",&p)`	Flash bytes Stack bytes MCU clocks	1570 (1458) 22 1237	1472 (1362)	1456 (1346) 22 971
`strtol ("12345",&p,0)`	Flash bytes Stack bytes MCU clocks	942 (830) 29 1074	874 (764)	808 (698) 21 722

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

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