From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Thierry Volpiatto <thierry.volpiatto@gmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: remove-duplicates performances
Date: Fri, 20 May 2011 11:09:55 -0300 [thread overview]
Message-ID: <jwvr57tv52f.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <877h9lv5tl.fsf@gmail.com> (Thierry Volpiatto's message of "Fri, 20 May 2011 15:51:02 +0200")
> i just noticed that `remove-duplicates' is very slow.
It's using an O(N²) algorithm, so it's indeed slow for long lists.
> (setq A (let ((seq (loop for i from 1 to 10000 collect i)))
> (append seq seq)))
> (1 2 3 4 5 6 7 8 9 10 1 2 ...)
For such long lists, I fully expect it to be slow.
But for short lists, the overhead of constructing a hash-table should
make the current code competitive. Can you try and find out for which
lengths your code is better than the one we have?
Stefan
next prev parent reply other threads:[~2011-05-20 14:09 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-20 13:51 remove-duplicates performances Thierry Volpiatto
2011-05-20 14:09 ` Stefan Monnier [this message]
2011-05-20 14:39 ` Thierry Volpiatto
2011-05-20 16:14 ` Stefan Monnier
2011-05-20 17:46 ` Thierry Volpiatto
2011-05-20 15:16 ` Ted Zlatanov
2011-05-20 14:28 ` David Kastrup
2011-05-20 16:00 ` Thierry Volpiatto
2011-05-20 17:01 ` David Kastrup
2011-05-20 17:31 ` Thierry Volpiatto
2011-05-20 17:46 ` David Kastrup
2011-05-20 18:01 ` Stefan Monnier
2011-05-20 21:57 ` Pascal J. Bourguignon
2011-05-20 17:57 ` Ted Zlatanov
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