From: Yusuke ENDOH <mame@...>
Date: 2009-12-02T02:19:33+09:00
Subject: [ruby-core:26978] Re: Caching #to_s for immutables (and a 	possible future for constant-folding) [with patch v2]

Hi,

2009/12/1 Kurt Stephens <ks@kurtstephens.com>:
>  I fixed issues uncovered by running make test-all.  There were a few tests
> and modules that assumed Symbol#to_s was mutable -- #method_missing appears
> to be a hot-bed for this assumption.  There were 7 common failures between
> the patched code and the svn trunk:
>
> WITHOUT THE PATCH:
>
> real    5m19.335s
> user    2m15.804s
> sys     0m35.850s
>
> WITH THE PATCH:
>
> real    4m37.127s
> user    1m51.243s
> sys     0m33.454s
>
> Approx 14% faster.


This is really interesting result, but the impact of the spec change seems
not to be small.  I guess that it may be acceptable for Ruby 2.0, but NG
for 1.8 and 1.9.

How about if #to_s returns, instead of a frozen String itself, a mutable
String that is duplicated from the cached frozen String?  Become less
effective than now?

-- 
Yusuke ENDOH <mame@tsg.ne.jp>