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Re: CVS directories in completion-ignored-extensions

From: Kim F. Storm
Subject: Re: CVS directories in completion-ignored-extensions
Date: Wed, 19 Jan 2005 16:52:28 +0100
User-agent: Gnus/5.11 (Gnus v5.11) Emacs/21.3.50 (gnu/linux)

Stefan Monnier <address@hidden> writes:

>> To me it seems like the regexp cache could be improved by
>> keeping a usage counter and a lru timestamp so frequently
>> used regexps could be kept in the cache -- and the cache
>> could grow dynamically to always hold the most frequently
>> used regexps [with some hard upper limit of course].
> A cheap way to approximate something like that is to keep a `hit' flag
> indicating whether this cache entry has ever been re-used.  Upon GC remove
> all entries for which `hit' is false and reset all `hit' flags to false.

And just reuse entries in the current LRC (least recently compiled)
way if we reach the hard limit.

> I.e. only those entries that have been reused since the last GC survive.
>> E.g. if I have a large number of regexps to split mail in gnus,
>> it would be nice to keep all of those in the cache.
> But of course a larger cache means slower lookup.

We can optimize that quite a bit, e.g. by hashing on SCHARS (pattern).

We could also optimize this test:

      if (SCHARS (cp->regexp) == SCHARS (pattern)
          && STRING_MULTIBYTE (cp->regexp) == STRING_MULTIBYTE (pattern)
          && !NILP (Fstring_equal (cp->regexp, pattern))

with this test:

      if ((EQ (cp->regexp, pattern)
           || (SCHARS (cp->regexp) == SCHARS (pattern)
               && STRING_MULTIBYTE (cp->regexp) == STRING_MULTIBYTE (pattern)
               && !NILP (Fstring_equal (cp->regexp, pattern))))

Kim F. Storm <address@hidden> http://www.cua.dk

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