From: Robert Pluim <rpluim@gmail.com>
To: emacs-devel@gnu.org
Subject: string_char_to_byte and string_byte_to_char micro-optimisation
Date: Fri, 14 Jun 2019 14:37:58 +0200 [thread overview]
Message-ID: <m28su41gwp.fsf@gmail.com> (raw)
Hi,
in <https://nullprogram.com/blog/2019/05/29/> a benchmark is shown:
(defun compare (string-a string-b)
(cl-loop for a being the elements of string-a
for b being the elements of string-b
unless (eql a b)
return (cons a b)))
(benchmark-run
(let ((a (make-string 100000 0))
(b (make-string 100000 0)))
(setf (aref a (1- (length a))) 256
(aref b (1- (length b))) 256)
(compare a b)))
which runs very slowly because string_char_to_byte and
string_byte_to_char only cache the found values for 1 previous string.
I have a patch which extends this cache to two (count 'em, two!)
previous strings, which fixes this particular benchmark.
What I donʼt have is any intuition on whether such a change actually
makes any difference in real-world Emacs usage. Can anyone suggest any
benchmarks?
Thanks
Robert
next reply other threads:[~2019-06-14 12:37 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-14 12:37 Robert Pluim [this message]
2019-06-14 16:53 ` string_char_to_byte and string_byte_to_char micro-optimisation Paul Eggert
2019-06-14 19:00 ` Eli Zaretskii
2019-06-14 20:11 ` Stefan Monnier
2019-06-15 6:22 ` Eli Zaretskii
2019-06-15 7:48 ` Stefan Monnier
2019-06-15 11:11 ` Noam Postavsky
2019-06-16 11:17 ` Stefan Monnier
2019-06-17 9:37 ` Robert Pluim
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