benchmarks(3)

NAME
benchmarks - 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 (82)
2
155 78 (78)
 74 (74)
2
149 atol ('12345') Flash bytes
Stack bytes
MCU clocks 122 (122)
2
221 118 (118)
 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 (150)
4
1172 134 (134)
 134 (134)
4
1152 ltoa (12345L, s, 10) Flash bytes
Stack bytes
MCU clocks 220 (220)
9
3174 200 (200)
 200 (200)
9
3136 malloc (1) Flash bytes
Stack bytes
MCU clocks 554 (554)
4
196 506 (506)
 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