From: "Óscar Fuentes" <ofv@wanadoo.es>
To: emacs-devel@gnu.org
Subject: Re: fix for bug 10994 breaks ido customizations in major way
Date: Sun, 05 May 2013 17:26:08 +0200 [thread overview]
Message-ID: <87ip2xsb1r.fsf@wanadoo.es> (raw)
In-Reply-To: 87y5btjy6v.fsf@uwakimon.sk.tsukuba.ac.jp
"Stephen J. Turnbull" <stephen@xemacs.org> writes:
> Óscar Fuentes writes:
>
> > So it seems that delete-dups is faster for strings than symbols.
>
> My interpretation is different: something is broken in the benchmarks
> (or in the estimate that the CPUs are of comparable performance).
I estimated that the CPUs are of similar performance because Leo reports
2 seconds for 10321 items and here it takes 12.5 seconds for 27000
items. Then items count ratio is 27000/10321 = 2.6, time ratio is 12.5/2
= 6.25 and the expected time ratio given O(n^2) complexity for the same
CPU is 2.6^2 = 6.76.
However,
(let ((choices))
(dotimes (i 10321)
(push (make-symbol (format "s%d" i)) choices))
(benchmark-run 10 (delete-dups choices)))
takes 6.26 seconds which is quite faster than the 19.9 seconds reported
by Leo. Maybe a L2 cache effect (2.4GHz Intel Q6600 with 4 MB L2 cache
for each pair of cores.)
> Comparing symbols for equality is a pointer comparison. Comparing
> strings for equality is a pointer comparison, followed by more work
> (some variation on a memcmp) in case of failure.
Yep. A similar benchmark with strings instead of symbols:
(let ((choices))
(dotimes (i 10321)
(push (format "%d" i) choices))
(benchmark-run 10 (delete-dups choices)))
takes 15.2 seconds, 1.5 per iteration.
Now, why delete-dups takes just 0.7 seconds for a list of strings a bit
*larger* than the one used above? The only difference is that those
strings follow the pattern directory/filename (it's the output of `git
ls-files')
However, the real issue being discussed here is if avoiding the overhead
of delete-dups on ido-completing-read warrants breaking some extensions
on a catastrophic way.
next prev parent reply other threads:[~2013-05-05 15:26 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-02 17:57 fix for bug 10994 breaks ido customizations in major way Le Wang
2013-05-03 4:13 ` Leo Liu
2013-05-03 12:49 ` Le Wang
2013-05-03 20:33 ` Leo Liu
2013-05-04 7:00 ` Le Wang
2013-05-04 8:58 ` Óscar Fuentes
2013-05-04 13:00 ` Le Wang
2013-05-05 10:57 ` Óscar Fuentes
2013-05-05 11:39 ` Leo Liu
2013-05-05 12:20 ` Óscar Fuentes
2013-05-05 12:58 ` Leo Liu
2013-05-05 13:38 ` Óscar Fuentes
2013-05-05 14:31 ` Stephen J. Turnbull
2013-05-05 15:26 ` Óscar Fuentes [this message]
2013-05-06 15:11 ` Le Wang
2013-05-06 22:49 ` Vitalie Spinu
2013-05-07 1:01 ` Óscar Fuentes
2013-05-07 9:35 ` Le Wang
2013-05-07 10:26 ` Vitalie Spinu
2013-05-07 10:35 ` Óscar Fuentes
2013-05-07 14:49 ` Le Wang
2013-05-07 21:18 ` Stefan Monnier
2013-05-07 14:42 ` Le Wang
2013-05-07 14:44 ` Drew Adams
2013-05-07 14:47 ` Le Wang
2013-05-07 19:00 ` Vitalie Spinu
2013-05-07 19:53 ` Óscar Fuentes
2013-05-08 0:04 ` Leo Liu
2013-05-08 0:35 ` Le Wang
2013-05-08 3:10 ` Leo Liu
2013-05-08 3:29 ` Leo Liu
2013-05-08 4:49 ` Leo Liu
2013-05-08 8:14 ` Vitalie Spinu
2013-05-08 8:42 ` Leo Liu
2013-05-08 12:23 ` Le Wang
2013-05-08 14:29 ` Leo Liu
2013-05-08 20:56 ` Juri Linkov
2013-05-10 1:52 ` Leo Liu
2013-05-17 2:48 ` Leo Liu
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