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[Gcl-devel] Re: Two word cons

From: Paul F. Dietz
Subject: [Gcl-devel] Re: Two word cons
Date: Fri, 20 May 2005 07:27:25 -0500
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.8) Gecko/20050511

Camm Maguire wrote:
Greetings, and thanks for the feedback!

"Paul F. Dietz" <address@hidden> writes:


  Judging by the space allocation numbers from TIME, objects
are also constrained to be an even number of words in Allegro CL
and in SBCL.  I think this is a common idea.

  If you have an extra field in some objects, consider uses for
it.  For example, we might want to precompute a hash key
for symbols (based on the package and symbol-name) if we're not
doing this already.  This could speed up SXHASH and EQ/EQL hash tables,
as well as CASE forms on symbols (switch on the hash key).

Great ideas!  Do I take it that you feel such a change (along the
lines described below) is beneficial on both 32bit and 64bit machines?
Am I missing anything key/important in the design considerations?

I think it would be.  SBCL does it for both sizes.  They cache
the SXHASH for symbols into the symbol rather than precomputing
it (and the hash doesn't depend on the package), but the idea
is similar.


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