Python frozenset hashing algorithm / implementation

Question

I\'m currently trying to understand the mechanism behind the hash function defined for Python\'s built-in frozenset data type. The implementation is shown at t

Answer 1

In

(h ^ (h << 16) ^ 89869747) * 3644798167

the multiplicative integer is a large prime to reduce collisions. This is especially relevant since the operation is under modulo.

The rest is probably arbitrary; I see no reason for the 89869747 to be specific. The most important usage you would get out of that is enlarging hashes of small numbers (most integers hash to themselves). This prevents high collisions for sets of small integers.

That's all I can think of. What do you need this for?