Re: hashed waitqueues

William Lee Irwin III
2002-01-16T17:43:36Z

On Wed, Jan 16, 2002 at 02:21:41PM +0000, Jamie Lokier wrote:
> Looking up "good hash function" on Google leads to these notable pages:
[various URL's]
> The last one is interesting because it mentions the golden prime
> multiplier function, and suggests good non-multipler functions instead.
> (Justification: the multiplier function doesn't distribute bits evenly).

Excellent! I can always use more of these to test.

It seems odd that they don't like Fibonacci hashing, it appears to pass
various chi^2 tests on bucket distribution. And operator-sparse Fibonacci
hashing primes appear to pass it as well, at least once 10 terms of the
continued fraction match (operator-sparse Fibonacci hashing primes means
that the multiplication can be done with shifts and adds or subtracts).

Regardless, various arches want non-multiplicative hash functions and
they'll be getting them. These hash functions will certainly prove
useful in getting a broader base to test against. I don't care to have
a "pet" hash function, only one that is good as possible.

Thanks,
Bill