bug#43598: replace-in-string: finishing touches

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

> Thanks.  Is it possible to have some speed comparison for these two?

This is what I used:

(let ((elems (mapcar (lambda (s)
                       (let ((start (random 80)))
                         (cons (substring s start (+ start (random 20)))
                               s)))
                     (cl-loop repeat 1000
                              collect (cl-coerce
                                       (cl-loop repeat 100
                                                collect (+ (random 26) ?a))
                                       'string)))))
  (list
   (benchmark-run 10000 (dolist (elem elems)
                          (string-search (car elem) (cdr elem))))
   (benchmark-run 10000 (dolist (elem elems)
                          (string-match (car elem) (cdr elem))))))

=>
((7.47099299 29 3.773541741999992)
 (19.673036086 74 9.616665831000006))

This is rather geared towards the weaknesses of string-match, though --
we're blowing through the regexp cache.

If you decrease the number of regexps to 10 and the run to 1000000, we get:

((7.818917279000001 37 4.791844609999998)
 (11.049133279 37 4.713127558000011))

And to compare with a "do-nothing" version:

   (benchmark-run 10000 (dolist (elem elems)
                          elem))))

=>

((5.74714395 28 3.722243896000009))

Using that as a baseline, the difference is 2s vs 5.2s.  

-- 
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   bloggy blog: http://lars.ingebrigtsen.no