From: Brian Candler <b.candler@...>
Date: 2008-09-25T18:25:53+09:00
Subject: Re: Hash optimization question

> I haven't looked into Ruby's Hash iterating in detail but it might be
> slower because of a general properties of hash tables: they are
> usually bigger (i.e. have more buckets) than the number of elements in
> the hash to allow for efficient hashing. Now if there are no links
> between hash entries (whose maintenance I believe would increase
> insertion overhead) iteration needs to access each hash bucket even
> those with no data in.  That might account for the slower runtimes.

Aside: ruby-1.9 keeps links between hash entries, exactly for the 
purpose of faster iteration. It also has the potentially useful 
side-effect that hashes iterate in the same order that the entries were 
inserted.

(However, depending on this feature is a good way of writing code which 
won't run properly in 1.8)
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