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Use a faster way to count 1's (used by Hamming)

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This commit is contained in:
Peng Xiao 2013-04-13 14:34:30 +08:00
parent f2dc445412
commit 6dd6013546
1 changed files with 5 additions and 8 deletions
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13
modules/ocl/src/opencl/brute_force_match.cl
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@ -62,15 +62,12 @@
#define DIST_TYPE 0
#endif
int bit1Count(int x)
//http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel
int bit1Count(int v)
{
int c = 0;
for (int i = 0 ; i < 32 ; i++)
{
c += x & 1;
x >>= 1;
}
return c;
v = v - ((v >> 1) & 0x55555555); // reuse input as temporary
v = (v & 0x33333333) + ((v >> 2) & 0x33333333); // temp
return ((v + (v >> 4) & 0xF0F0F0F) * 0x1010101) >> 24; // count
}
// dirty fix for non-template support