From: ludo@gnu.org (Ludovic Courtès)
To: guile-devel@gnu.org
Subject: Re: [PATCH] Efficient Gensym Hack
Date: Sat, 10 Mar 2012 23:55:59 +0100 [thread overview]
Message-ID: <87pqck83r4.fsf@gnu.org> (raw)
In-Reply-To: 87mx7vx8zg.fsf@netris.org
Hi Mark,
Just a few questions.
Mark H Weaver <mhw@netris.org> skribis:
> Here's an implementation of the efficient gensym hack for stable-2.0.
> It makes 'gensym' about 4.7 times faster on my Yeeloong. Gensyms are
> not given names or even numbers until they are asked for their names or
> hash values (for 'equal?' hash tables only).
Ooooh, I only really understood when seeing this:
+ return scm_double_cell (scm_tc7_symbol | SCM_I_F_SYMBOL_LAZY_GENSYM,
+ SCM_UNPACK (prefix_stringbuf), (scm_t_bits) 0,
+ SCM_UNPACK (scm_cons (SCM_BOOL_F, SCM_EOL)));
So you can actually ‘eq?’ or ‘hashq’ them regardless of whether they
have a name, nice! :-)
> The first patch adds an optimization for strings that is important for
> gensyms. It avoids locking a mutex when setting the shared flag on a
> stringbuf if the shared flag is already set.
How much impact does this have? Thanks to futexes, mutex_lock should be
fairly cheap when there’s no contention, no?
Nice work!
Thanks,
Ludo’.
prev parent reply other threads:[~2012-03-10 22:55 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-05 17:17 [PATCH] Efficient Gensym Hack Mark H Weaver
2012-03-05 21:52 ` Andy Wingo
2012-03-06 3:16 ` Mark H Weaver
2012-03-06 8:56 ` Andy Wingo
2012-03-06 9:55 ` [PATCH] Efficient Gensym Hack (v2) Mark H Weaver
2012-03-07 10:40 ` Andy Wingo
2012-03-07 16:43 ` Mark H Weaver
2012-03-07 17:25 ` Andy Wingo
2012-03-07 19:28 ` Mark H Weaver
2012-03-07 20:04 ` Andy Wingo
2013-01-16 17:25 ` Andy Wingo
2012-03-10 22:55 ` Ludovic Courtès [this message]
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