From: Lionel Bouton <lionel-subscription@...>
Date: 2007-08-27T03:31:23+09:00
Subject: Re: sort_by { rand } not working

James Edward Gray II wrote:
>
> It would be better to use:
>
> data = data.sort_by { … }

I was wondering about a crazy idea of mine: "sort!{rand<=>rand}" and
from my bench results it's a waste of time (it's even dangerous, see
below). I suspect sort_by begins by mapping the block results and then
sorts based on the map (it's roughly 4x faster than sort!{ rand <=> rand }).
sort!{rand<=>rand} obviously can't do that and must call the block each
time a comparison must be done (I suspect that more rand calls make it
slower even if it can avoid copying things and instead do in-place
modifications ... or that the Ruby sort algorithm doesn't like
comparison results changing...).

Obviously depending on the sort algorithm used it might not even
converge on a result (the dangerous part...).

Lionel