Last time I needed high occupancy I was for a cache. So I've stirred my 32b keys with Phi-mul-rshift and randomly (xor-shift) displaced picked slot old value by

Last time I needed high occupancy I was for a cache. So I've stirred my 32b keys with Phi-mul-rshift and randomly (xor-shift) displaced picked slot old value by log2(size)/2 with linear probing of up to log2(size).