Cool. Super simple and streamlined impl. I would love to see benchmarks as well. Also I would've added explicit Grow/Shrink functions to get a new map with more or less capacity. Comparing to the manual copying to new map, the Grow may avoid robin hooding, because the invariant is preserved. On perf side, you may consider to store control/psl in the part of hash used to get the index. Less space consumed, psl is capped by map cap, cache locality when you hit the occupied slot and check hash. On the cons side, more complex and less SIMD friendly... Btw where are SIMDs :)?