From: Eric Mahurin <eric.mahurin@...>
Date: 2007-10-26T01:40:56+09:00
Subject: Re: pop/push, shift/unshift

On 10/25/07, Bob Hutchison <hutch@recursive.ca> wrote:
> Hi,
>
> On 25-Oct-07, at 1:12 AM, Robert Dober wrote:
>
> > Well I guess I have to believe you, but I would *love* to reproduce it
> > if I do
> > times do
> >    <<
> > end
> > times do
> >   shift
> > end
> > it will leak?
>
> How else would you describe the 10k Things left in memory after the
> shifts in the modified version of your test case?


The problem is that Ruby's COW (copy-on-write) scheme is messed up for
arrays.  I've found much worse cases performance and memory-wise.  Try
doing a small #slice on a big array a bunch and modify the small
slices.  I made a 1.9 patch a couple years ago that fixed the problem
and made ALL operations near the front just as fast as the operations
on the back.  Unfortunately, it never made it in.  The way I did it
might be unique, not sure.  I thought C++ deque does something
similiar, but it doesn't.  When I find time, I'll try to do the fix
again.