3 ms·

Wouldn't that be two parallel vectors? (Side note: nobody ever thinks to bring up cache behavior in interviews where I ask about how a hash map could be impleme

• cesarb 9y ago
  > Wouldn't that be two parallel vectors? Yes, but it's a single contiguous memory allocation. (It used to be three parallel vectors in a single allocation, with keys and values also kept separate to avoid padding between them, but experiments showed that had worse cache behavior.) > How does that special hash marker work? What happens when something actually hashes to it? Just silently increment the hash? Looking at the code, it always sets the most significant bit of every real hash value (since the least significant bits select the bucket, it makes no difference), and the marker has the most significant bit clear (in fact, all bits of the marker value are clear).
  • a_t48 9y ago
    Oh, clever. Of course you can do it that way.