Subject: Re: [boost] unordered_map 32bit VS 64bit
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2012-01-26 06:16:47
On Thu, Jan 26, 2012 at 12:16 PM, Daniel James <dnljms_at_[hidden]> wrote:
> On 26 January 2012 07:51, Andrey Semashev <andrey.semashev_at_[hidden]> wrote:
>
>> IMHO, the best way to address this problem is to provide a set of
>> "good" hash functions for common types (I believe functional/hash
>> already does this) and possibly a wrapper function that just does bit
>> mixing in a user-provided hash function. Boost.Unordered docs should
>> mention these tools and advise to use them to get better performance.
>
> Actually functional/hash doesn't. It's good enough for the standard,
> but no better. For numbers that fit into the hash value, it just
> returns them unchanged which is fine for a prime number of buckets but
> not for power of 2 containers.
Well, we probably better fix functional/hash then?