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Very poor Lisp performance
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From: Jon Harrop <use...@jdh30.plus.com>
Subject: Re: Very poor Lisp performance
Newsgroups: comp.lang.lisp
Date: Sat, 13 Aug 2005 21:21:35 +0100
References: <42fd4459$0$97104$ed2619ec@ptn-nntp-reader03.plus.net> <HvSdnayKD_1M8mDfRVn-ow@speakeasy.net> <42fdd7a8$0$97130$ed2619ec@ptn-nntp-reader03.plus.net> <slrndfsf3v.p65.jsnell@sbz-31.cs.Helsinki.FI>
Organization: Flying Frog Consultancy Ltd.
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Juho Snellman wrote:
> <use...@jdh30.plus.com> wrote:
>>>> My system is an unladen 900MHz Athlon T-bird with 768Mb RAM running
>>>> Debian testing with SBCL 0.8.16 and CMUCL "19b-release-20050628-3 +
>>>> minimal debian patches".
>
> That's a rather ancient version of SBCL, you might want to upgrade.
Debian unstable has 0.9.3. It's upgrading now... :-)
> For example:
>
>> (defstruct (vec (:conc-name nil) (:constructor vec (x y z)))
>> (x 0.0 :type single-float)
>> (y 0.0 :type single-float)
>> (z 0.0 :type single-float))
>
> This is using about 2x the memory of what you'd expect for each
> instance, and doing an extra memory indirection for each slot access.
> Proper support for storing the floats "raw" in the struct was added in
> 0.9.2 by David Lichteblau.
I see.
> Another possible pitfall on older SBCLs (<0.8.21) is that they don't
> honor the compiler policy for code entered on the repl, but compile it
> with low speed, high debug/safety. If you've been pasting the code
> into the repl instead of LOADing it, performance would indeed be
> horrible.
Aha! Yes indeed. I just tried (load (compile-file "...")) and it runs in
only 20secs compared to ~250secs from the top-level and 2.5secs for C++.
Thanks for the help. I'll repost when I get results with the new compiler.
--
Dr Jon D Harrop, Flying Frog Consultancy
http://www.ffconsultancy.com
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