/*
Blink: Function vs LookUp Table Benchmark
Changes the state of an LED,
and performs thousands of function calls repeatedly.
*/
// Use the following line to use LUT. Comment it for regular function
//#define USE_LUT
// Use the following line to calculate logarithm. Comment it for squares
#define USE_LOG
// Use the following line to report back to the serial monitor
#define MEASURE
#define MASK(x) ((unsigned char)(1<<(x)))
#ifdef MEASURE
uint32_t StartTime, CurrentTime;
#endif
#ifdef USE_LUT
#ifdef USE_LOG
// LookUp Table for the base 10 logarithm of 0 through 255
const double log_LUT[256] = {-1.0E30, 0.000000, 0.301030, 0.477121, 0.602060,
0.698970, 0.778151, 0.845098, 0.903090, 0.954243, 1.000000, 1.041393, 1.079181,
1.113943, 1.146128, 1.176091, 1.204120, 1.230449, 1.255273, 1.278754, 1.301030,
1.322219, 1.342423, 1.361728, 1.380211, 1.397940, 1.414973, 1.431364, 1.447158,
1.462398, 1.477121, 1.491362, 1.505150, 1.518514, 1.531479, 1.544068, 1.556303,
1.568202, 1.579784, 1.591065, 1.602060, 1.612784, 1.623249, 1.633468, 1.643453,
1.653213, 1.662758, 1.672098, 1.681241, 1.690196, 1.698970, 1.707570, 1.716003,
1.724276, 1.732394, 1.740363, 1.748188, 1.755875, 1.763428, 1.770852, 1.778151,
1.785330, 1.792392, 1.799341, 1.806180, 1.812913, 1.819544, 1.826075, 1.832509,
1.838849, 1.845098, 1.851258, 1.857332, 1.863323, 1.869232, 1.875061, 1.880814,
1.886491, 1.892095, 1.897627, 1.903090, 1.908485, 1.913814, 1.919078, 1.924279,
1.929419, 1.934498, 1.939519, 1.944483, 1.949390, 1.954243, 1.959041, 1.963788,
1.968483, 1.973128, 1.977724, 1.982271, 1.986772, 1.991226, 1.995635, 2.000000,
2.004321, 2.008600, 2.012837, 2.017033, 2.021189, 2.025306, 2.029384, 2.033424,
2.037426, 2.041393, 2.045323, 2.049218, 2.053078, 2.056905, 2.060698, 2.064458,
2.068186, 2.071882, 2.075547, 2.079181, 2.082785, 2.086360, 2.089905, 2.093422,
2.096910, 2.100371, 2.103804, 2.107210, 2.110590, 2.113943, 2.117271, 2.120574,
2.123852, 2.127105, 2.130334, 2.133539, 2.136721, 2.139879, 2.143015, 2.146128,
2.149219, 2.152288, 2.155336, 2.158362, 2.161368, 2.164353, 2.167317, 2.170262,
2.173186, 2.176091, 2.178977, 2.181844, 2.184691, 2.187521, 2.190332, 2.193125,
2.195900, 2.198657, 2.201397, 2.204120, 2.206826, 2.209515, 2.212188, 2.214844,
2.217484, 2.220108, 2.222716, 2.225309, 2.227887, 2.230449, 2.232996, 2.235528,
2.238046, 2.240549, 2.243038, 2.245513, 2.247973, 2.250420, 2.252853, 2.255273,
2.257679, 2.260071, 2.262451, 2.264818, 2.267172, 2.269513, 2.271842, 2.274158,
2.276462, 2.278754, 2.281033, 2.283301, 2.285557, 2.287802, 2.290035, 2.292256,
2.294466, 2.296665, 2.298853, 2.301030, 2.303196, 2.305351, 2.307496, 2.309630,
2.311754, 2.313867, 2.315970, 2.318063, 2.320146, 2.322219, 2.324282, 2.326336,
2.328380, 2.330414, 2.332438, 2.334454, 2.336460, 2.338456, 2.340444, 2.342423,
2.344392, 2.346353, 2.348305, 2.350248, 2.352183, 2.354108, 2.356026, 2.357935,
2.359835, 2.361728, 2.363612, 2.365488, 2.367356, 2.369216, 2.371068, 2.372912,
2.374748, 2.376577, 2.378398, 2.380211, 2.382017, 2.383815, 2.385606, 2.387390,
2.389166, 2.390935, 2.392697, 2.394452, 2.396199, 2.397940, 2.399674, 2.401401,
2.403121, 2.404834, 2.406540};
#else
// LookUp Table for the square of 0 through 255
const uint32_t sq_LUT[256] = {0, 1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144,
169, 196, 225, 256, 289, 324, 361, 400, 441, 484, 529, 576, 625, 676, 729, 784,
841, 900, 961, 1024, 1089, 1156, 1225, 1296, 1369, 1444, 1521, 1600, 1681, 1764,
1849, 1936, 2025, 2116, 2209, 2304, 2401, 2500, 2601, 2704, 2809, 2916, 3025,
3136, 3249, 3364, 3481, 3600, 3721, 3844, 3969, 4096, 4225, 4356, 4489, 4624,
4761, 4900, 5041, 5184, 5329, 5476, 5625, 5776, 5929, 6084, 6241, 6400, 6561,
6724, 6889, 7056, 7225, 7396, 7569, 7744, 7921, 8100, 8281, 8464, 8649, 8836,
9025, 9216, 9409, 9604, 9801, 10000, 10201, 10404, 10609, 10816, 11025, 11236,
11449, 11664, 11881, 12100, 12321, 12544, 12769, 12996, 13225, 13456, 13689,
13924, 14161, 14400, 14641, 14884, 15129, 15376, 15625, 15876, 16129, 16384,
16641, 16900, 17161, 17424, 17689, 17956, 18225, 18496, 18769, 19044, 19321,
19600, 19881, 20164, 20449, 20736, 21025, 21316, 21609, 21904, 22201, 22500,
22801, 23104, 23409, 23716, 24025, 24336, 24649, 24964, 25281, 25600, 25921,
26244, 26569, 26896, 27225, 27556, 27889, 28224, 28561, 28900, 29241, 29584,
29929, 30276, 30625, 30976, 31329, 31684, 32041, 32400, 32761, 33124, 33489,
33856, 34225, 34596, 34969, 35344, 35721, 36100, 36481, 36864, 37249, 37636,
38025, 38416, 38809, 39204, 39601, 40000, 40401, 40804, 41209, 41616, 42025,
42436, 42849, 43264, 43681, 44100, 44521, 44944, 45369, 45796, 46225, 46656,
47089, 47524, 47961, 48400, 48841, 49284, 49729, 50176, 50625, 51076, 51529,
51984, 52441, 52900, 53361, 53824, 54289, 54756, 55225, 55696, 56169, 56644,
57121, 57600, 58081, 58564, 59049, 59536, 60025, 60516, 61009, 61504, 62001,
62500, 63001, 63504, 64009, 64516, 65025};
#endif
#else
#ifndef USE_LOG
// Regular function for the square of 0 through 255
uint32_t sq_func(uint8_t x){
return (uint32_t)x*x;
}
#endif
#endif
// x is a placeholder variable to make use of the functions/LUTs
// It's a double for logarithms, and a 32 bit integer for squares
#ifdef USE_LOG
volatile double x = 0.0;
#else
volatile uint32_t x = 0;
#endif
void setup()
{
DDRB |= MASK(5); // The LED pin is output. Mask: 00100000
Serial.begin(9600);
}
void loop()
{
PORTB ^= MASK(5); // Toggle LED
// j is the main loop variable. Logarithms take longer, so different values are used.
#ifdef USE_LOG
uint32_t j = 100;
#else
uint32_t j = 600;
#endif
#ifdef MEASURE
StartTime = millis();
#endif
while (j--)
for (uint8_t i = 0; i < 255; i++) { // Call functions 255 times, according to #define symbols
#ifdef USE_LUT
#ifdef USE_LOG
x = log_LUT[i]; // Using base 10 logarithm LookUp Table
#else
x = sq_LUT[i]; // Using square LookUp Table
#endif
#else
#ifdef USE_LOG
x = log10(i); // Using base 10 logarithm function from math.h
#else
x = sq_func(i); // Using square function, defined above
#endif
#endif
}
#ifdef MEASURE
CurrentTime = millis();
Serial.print("Took ");
Serial.print((float)(CurrentTime - StartTime) * 0.001, 3);
Serial.print(" seconds\n");
#endif
}