About built-in AAs

[Josh Simmons]

On Fri, Aug 19, 2011 at 1:43 AM, Sean Kelly <sean at invisibleduck.org> wrote:
> This sounds like an application design issue rather than a language issue. Do any languages use a pool of hash routines like this?
>
> Sent from my iPhone
>
> On Aug 17, 2011, at 5:06 PM, Josh Simmons <simmons.44 at gmail.com> wrote:
>
>> On Thu, Aug 18, 2011 at 8:40 AM, Sean Kelly <sean at invisibleduck.org> wrote:
>>> On Aug 17, 2011, at 2:36 PM, bearophile wrote:
>>>
>>>> Walter:
>>>>
>>>>> Bottom line, I don't think there's an actual problem here.
>>>>
>>>> Thank you for your answers. And I agree that the current situation is overall better than the precedent one.
>>>>
>>>> My original first post of this thread was about other problems, quite more practical ones, like receiving help from the compiler if I am using hash protocol badly, etc. :-)
>>>
>>> This would be a run-time issue, unless you're asking the compiler to verify your hash algorithm at compile-time :-p  I'd actually like to have some introspection functionality so I could find out the average chain length, max chain length, etc (basically what's provided by the unordered containers from C++11), but the user would still have to query this stuff to know that something was wrong.
>>
>> The security issue is basically a DoS one, for example if you know a
>> web server is using a specific hash and collision resolution method to
>> store message headers you can pass headers that all hash to buckets
>> that provide worst-case behavior. In this instance universal hashing
>> where a hash function is chosen randomly from a pool of hashes
>> combined with good algorithmic complexity means the attacker is unable
>> to do this reliably.
>>
>> Unrelated though, I'm quite a fan of hopscotch hashing at the moment,
>> in theory at least. It'd be interesting to get a few different
>> resolution schemes working and compare their performance on various
>> workloads.
>

I doubt it, I was just noting the issue not suggesting it should be fixed.

Cheers,
Josh.