* Re: c-beginning-of-defun in the past and presence
2014-09-21 9:36 c-beginning-of-defun in the past and presence martin rudalics
@ 2014-09-24 22:25 ` Alan Mackenzie
0 siblings, 0 replies; 2+ messages in thread
From: Alan Mackenzie @ 2014-09-24 22:25 UTC (permalink / raw)
To: martin rudalics; +Cc: emacs-devel
Hi, Martin.
On Sun, Sep 21, 2014 at 11:36:34AM +0200, martin rudalics wrote:
> Dear Alan and friends
> Running with emacs -Q
> (with-current-buffer (find-file-noselect "~/src/xdisp.c")
> (elp-instrument-function 'c-beginning-of-defun)
> (goto-char (point-max))
> (condition-case nil
> (beginning-of-defun 1000)
> (error nil))
> (elp-results))
> gets me here as elapsed time
> Emacs 24.3: 1.672
> Emacs 24.4: 4.516
> Emacs trunk: 27.375
> Running with emacs -Q
> (with-current-buffer (find-file-noselect "~/src/xdisp.c")
> (elp-instrument-function 'c-beginning-of-defun)
> (goto-char (point-max))
> (condition-case nil
> (while (beginning-of-defun) nil)
> (error nil))
> (elp-results))
> gets me here
> Call Count Elapsed Time Average Time
> Emacs 24.3: 353 23.842999999 0.0675439093
> Emacs 24.4: 353 43.000000000 0.1218130311
> Emacs trunk: 353 136.48399999 0.3866402266
> Please try to make things behave reasonably again.
, for some value of "reasonably". ;-)
I've repeated your timings for the first case (i.e. (beginning-of-defun
1000)) and get pretty much the same results you do.
What is taking the time in the trunk is (presumably) backwards
`scan-lists's, which you can see if you elp-instrument `scan-lists' too.
It is taking longer since Emacs-23 because
`open-paren-in-column-0-is-defun-start' is being bound to nil in
`c-parse-state' to avoid buggy processing. But I think you know this
anyway.
Stefan committed revision 117351 on 2014-07-04 to the Emacs-24 branch,
which should have helped. This should have been merged into the trunk by
revision 117499, committed by Glenn on 2014-07-08, and looking at the
source code, it appears it did. I don't know, at this stage, why the
trunk is so much slower that the Emacs-24 branch. I'll need to have a
look at this.
In the second case ((while (beginning-of-defun) nil)), it cannot but be
much slower than the first case, since the expensive analysis to move
from the top level '{' to BOD is repeated for every defun, rather than
just being done once, when c-beginning-of-defun is given its repeat
count. I expect the reason for the slow down between Emacs-24 and trunk
will turn out to be the same as for the first case.
> Thanks, martin
--
Alan Mackenzie (Nuremberg, Germany).
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