GNU bug report logs - #17049
[PATCH] Make reverse! forego the cost of SCM_VALIDATE_LIST

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From: David Kastrup <dak <at> gnu.org>
To: Andy Wingo <wingo <at> pobox.com>
Cc: 17049 <at> debbugs.gnu.org
Subject: bug#17049: [PATCH] Make reverse! forego the cost of SCM_VALIDATE_LIST
Date: Fri, 21 Mar 2014 18:44:07 +0100

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Andy Wingo <wingo <at> pobox.com> writes:

> Hi,
>
> Thanks for the patch.  What is its performance impact for your use case?

Here is an artificial use case (I make care to get my list scattered
over memory, assuming that sort! keeps the cells around).

[zoppo.scm (application/octet-stream, attachment)]

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The output for my version first and the default version afterwards is

#<time type: time-duration nanosecond: 449629000 second: 8>dak <at> lola:/usr/local/tmp/guile$ meta/guile /tmp/zoppo.scm 
#<time type: time-duration nanosecond: 898802000 second: 15>dak <at> lola:/usr/local/tmp/guile$ 

So it's a bit better than my 7:4 estimate (rather a factor of 1.88),
probably because I forgot that the CPU does not have to wait for the
write cycle to complete for continuing.

Now that's a somewhat artificial benchmark, but still: almost a factor
of 2 for the operation itself is pretty good.

-- 
David Kastrup

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