Re: [boost] [review] hash functions

From: Dave Harris (brangdon_at_[hidden])
Date: 2005-03-16 12:07:14

In-Reply-To: <01b201c52987$e0bbb950$6801a8c0_at_pdimov>
pdimov_at_[hidden] (Peter Dimov) wrote (abridged):
> If you _know_ how the default hash function will perform on your key 
> set, you can make the decision of whether to use it or not, and if the 
> hash function is standard, you do not have to re-evaluate your decision 
> each time you change platforms.

I do appreciate the benefits of stability. What isn't clear is whether it 
trumps hash quality. This is a judgement call, in that it partly depends 
on which issue is more important to you.

Ultimately if you want stability you can get it by using your own hasher. 
If you want the best quality the platform can deliver, then that's 
intrinsically non-portable; it should be provided by the vendor but in a 
standard way.

We could both be made happy if boost provided 2 hashers as standard, one 
for stability and one for quality. However, I don't think we want to go 
that route at this stage, and anyway there can only be one default.

This is /not/ a deal-breaker for me. I won't reject the proposal because 
it favours stability over hash quality.

-- Dave Harris, Nottingham, UK