> This is an incredibly poor design choice (at Facebook we'd say "clowntown") as it makes it unusable with any sophisticated hashtable data structure that assum

> This is an incredibly poor design choice (at Facebook we'd say "clowntown") as it makes it unusable with any sophisticated hashtable data structure that assumes reasonable randomness. That's what causes the quadratic growth in the sequential example with dense_hash_map. Nonsense. GCC developers have absolutely no way of knowing or guessing how the distribution of all integers map into the domain of positive integers. And any guess (without knowledge of the specific application domain) would have as many degenerate cases as the identity. Maybe heuristically Facebook found some better general purpose hashes for their use case. But "clowntown" is a denigration.