[Python-Dev] String hash function multiplier (original) (raw)

Raymond Hettinger raymond.hettinger at verizon.net
Tue Apr 13 19:59:53 EDT 2004


Does anyone have any issues with changing the hash multiplier for the string and Unicode hash functions?

Instead of 1000003, I would like to use Aho's 65599, a prime near 2**16 that is efficiently expressible as (x << 6) + (x << 16) - x. This replaces a multiply with fast adds and shifts (with the two shifts potentially being executed in parallel).

Googling for "hash 65599" shows a long history of widespread use and testing without any problems.

Raymond Hettinger



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