Hello
,
I'm running this test:
#include <stdio.h>
#include <math.h>
#include <time.h>
int hardlightOriginal(int image, int mask) {
return ((int)((image < 128) ? (2 * mask * image / 255):(255 - 2 * (255 - mask) * (255 - image) / 255)));
}
int hardlightOptimized(int image, int mask) {
return ((int)((image < 128) ? ((mask << 1) * image / 255):(255^( ((255^mask) << 1) * (255^image) / 255))));
}
int main(int argc, char *argv[])
{
int testImage[10] = {111,222,111,222,111,222,111,222,111,222};
int testMask[10] = {44,121,26,4,89,158,225,255,224,187};
int max_cases = 10000000;
clock_t start1,end1;
clock_t start2,end2;
// tests for perfomance
// at first original way
start1 = clock();
for (int j=0; j < max_cases; j++) {
for (int i=0; i < 10; i++) {
int res = hardlightOriginal(testImage[i],testMask[i]);
}
}
end1 = clock();
// now optimized way
start2 = clock();
for (int j=0; j < max_cases; j++) {
for (int i=0; i < 10; i++) {
int res = hardlightOptimized(testImage[i],testMask[i]);
}
}
end2 = clock();
long orgDiff = end1-start1;
long optDiff = end2-start2;
printf("Original %i , Optimized %i \n" , orgDiff, optDiff);
return 0;
}
which in essence compares execution speed of ordinary function hardlightOriginal(...) and hardlightOptimized(..), which is re-wrriten by using bitwise operators. My intuition tells my that hardlightOptimized(...) should be faster. Indeed if I run that with Ms Visual C++ - it is faster or at least at the same degree as not optimized function. Now when i run it with Pelles C - i get different resuts. Optimized function is SLOWER than original one. How this can happen that bitwise operations can't help to speed up application
I'm running on Windows 7, Intel Core 2 Duo.
Thanks
