STEPHEN bui STEPHEN bui - 16 days ago 9
C Question

Code didn't calculate the right time execution of function in C

I have searched for how to calculate the execution time of a program, and i have done exactly in describe of these topic

Execution time of C program

Calculating time of execution with time() function

but my code didn't count the time execution and i don't know why.
here are my code

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main(int argc, char** argv) {
time_t begin, end;
begin = clock();
int c = 0;
for (int i = 0; i < 255; i++) {
printf("%d ",c++);
}
end = clock();
printf("\n");
double timeTaken = ((double) (end - begin)) / CLOCKS_PER_SEC;
printf("time taken: %lf", timeTaken);
return (EXIT_SUCCESS);
}


here are what it printed

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53
54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78
79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102
103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121
122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140
141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159
160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178
179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197
198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216
217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235
236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254
time taken: 0.000000


I have checked many times for error, but it still print "time taken: 0.000000". Can you guys help me out? Thanks a lot.

Answer

Actually, you are iterating loop for a small number of times. Try iterating the loop for large number of times. Eg. iterate for 1e9 times. Then you will get noticeable time period. Modern processors are very fast, such that they have frequency upto 2.9 GHz or more, which mean that they can execute around 2 billion instructions, if available, within a second.