Bloom filters also have the unusual property that the time needed either to add items or to check whether an item is in the set is a fixed constant, O(), completely independent of the number of items already in the set. No other constant-space set data structure has this property, but the average access time of sparse hash tables can make them faster in practice than some Bloom filters. In a hardware implementation, however, the Bloom filter shines because its lookups are independent and can be parallelized.