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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 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 |