Re: Markers in a gap array

[Pip Cet <pipcet@protonmail.com>]

On Thursday, July 4th, 2024 at 20:11, Stefan Monnier <monnier@iro.umontreal.ca> wrote:
> Ihor Radchenko [2024-07-04 14:30:47] wrote:
> > Stefan Monnier monnier@iro.umontreal.ca writes:
> > 
> > > > Some perf stats:
> > > > 
> > > > ;; Switch to todo and mark next 3 times, on branch
> > > > ;; 28.72% emacs emacs
> > > > [.] markers_sanity_check
> > > 
> > > Did you build with or without assertions?
> > 
> > Without.
> > 
> > > And indeed, I need to rework them to be "more conditional" (but I was
> > > focused on correctness until now). You should probably remove those
> > > calls to `markers_sanity_check` by hand when testing performance, sorry.
> > 
> > Without these calls, I can see some speed improvement in
> > buf_bytepos_to_charpos, but I do not currently have a reliable
> > reproducer to trigger buf_bytepos_to_charpos slowdown on master, so it
> > is comparing very small numbers.
> 
> 
> Hmm... I tried a benchmark based on:
> 
> (defconst elb-bytechar-buffer
> (let ((buf (get-buffer-create " elb-bytechar")))
> (with-current-buffer buf
> (let ((step (apply #'concat "🙂 foo\n" (make-list 2000 "asdf "))))
> (dotimes (_ (/ 10000000 (length step)))
> (insert step))
> buf))))
> 
> (defconst elb-bytechar-re "\\<.\\> \\<.\\> bar")
> 
> 
> (defun elb-bytechar--aux (nmarkers lookup &optional marker-fun)
> (with-current-buffer elb-bytechar-buffer
> (let ((step (/ (buffer-size) nmarkers))
> (markers nil))
> (dotimes (i nmarkers)
> (push (copy-marker (funcall (or marker-fun #'identity) (* i step)))
> markers))
> (dotimes (_ 10)
> (goto-char (point-min))
> (let ((parse-sexp-lookup-properties lookup))
> (re-search-forward elb-bytechar-re nil t))))))
> 
> where I call `elb-bytechar--aux` with various arguments.

Could you share a more complete recipe for the benchmark? I wonder how it compares to Gerd's weak vector/freelist in scratch/igc.

I think this is very exciting, even though it might have been triggered by incorrectly-reported numbers of markers :-)

Pip