Fast hashtable

[deadalnix via Digitalmars-d]

On Tuesday, 28 February 2017 at 17:57:14 UTC, Andrei Alexandrescu 
wrote:
> This is of possible interest: 
> https://probablydance.com/2017/02/26/i-wrote-the-fastest-hashtable/ -- Andrei

> But let’s say you know that your hash function returns numbers 
> that are well distributed and that you’re rarely going to get 
> hash collisions even if you use powers of two.

In which case you don't need powers of 2 either.

ucent h = hash64(key);
ulong slot = (h * slotCount) >> 64;

And you get what you want, with no constraint on the number of 
slots. Note that on most architectures, this actually lowers to 
one mulhi operation, which is typically 3 cycles.