On Friday, 15 February 2013 at 02:26:31 UTC, Adam D. Ruppe wrote:
druntime has a hash implementation in module rt.util.hash that
looks pretty useful, but isn't publicaly exported by the
library anywhere.
Does phobos or druntime offer a public hash function like that?
If no, can it expose this one?
This might be a good time to bring up something that was
bothering me when I examined the current druntime hash
implementation. Just out of curiosity I was researching hash
functions, and I found the hash function expert Bob Jenkins' FAQ
about hashes:
http://burtleburtle.net/bob/hash/hashfaq.html
He says specifically that any hash function requiring a modulo
prime at the end is bad (inefficient), but if I'm not mistaken,
the druntime does just that. At line 50 of the associative array
module there is a list of primes, and I believe the
implementation assumes them to be necessary.
https://github.com/D-Programming-Language/druntime/blob/master/src/rt/aaA.d
I don't know enough to be sure this is a problem. There might be
some other reason for the modulo prime, but I'd like to put my
mind at ease on it.
