From: pjb@informatimago.com (Pascal J. Bourguignon)
To: help-gnu-emacs@gnu.org
Subject: Re: Vector and List Performance
Date: Tue, 09 Jun 2009 14:51:22 +0200 [thread overview]
Message-ID: <7cd49d6051.fsf@pbourguignon.anevia.com> (raw)
In-Reply-To: 4b62dc88-b861-4f9c-82d6-e175b2247c45@w40g2000yqd.googlegroups.com
Nordlöw <per.nordlow@gmail.com> writes:
> Aahh, we needed a macro instead:
>
> (defmacro bench (&rest forms)
> "Convenience wrapper for benchmark-run-compiled."
> `(let ((n 10))
> (/ (nth 0 (benchmark-run n ,@forms)) n)))
>
> This gives a reasonable difference in performance.
>
> By the way, does elisp lists have extra pointers to the middle of the
> list (a skip-list)?
No, because it wouldn't be efficient to have to maintain them.
(let* ((c (list 7 8 9))
(b (list* 4 5 6 c))
(a (list* 1 2 3 b)))
(push -1 (cddr c)) (push -2 (cddr c)) ; you may have to update a big number of skip-lists!
(list a b c))
-->
((1 2 3 . #1=(4 5 6 . #2=(7 8 -2 -1 9))) #1# #2#)
(deftype list () '(or null (cons t list))) ; nothing more.
--
__Pascal Bourguignon__
next prev parent reply other threads:[~2009-06-09 12:51 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-08 17:27 Vector and List Performance Nordlöw
2009-06-08 19:57 ` Tassilo Horn
2009-06-09 9:30 ` Pascal J. Bourguignon
2009-06-09 11:30 ` Nordlöw
2009-06-09 12:51 ` Pascal J. Bourguignon [this message]
2009-06-09 18:13 ` Nordlöw
2009-06-10 8:24 ` Pascal J. Bourguignon
[not found] ` <7c63f45we1.fsf@pbourguignon.informatimago.com>
2009-06-10 8:36 ` Pascal J. Bourguignon
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