SFB_BUCKET_SHIFT
sfbhash >>= SFB_BUCKET_SHIFT;
sfbhash >>= SFB_BUCKET_SHIFT;
sfbhash >>= SFB_BUCKET_SHIFT;
#define SFB_NUMBUCKETS (1 << SFB_BUCKET_SHIFT) /* N bins per Level */
#define SFB_LEVELS (32 / SFB_BUCKET_SHIFT) /* L */
sfbhash >>= SFB_BUCKET_SHIFT;