WORD_OFFSET_BITS
#define WORD_OFFSET_MASK ((1 << WORD_OFFSET_BITS) - 1)
#define SWEEP_ID_BITS (WORD_BITS - (THREAD_ID_BITS + WORD_OFFSET_BITS))
#define THREAD_ID_SHIFT (WORD_OFFSET_BITS + SWEEP_ID_BITS)