GNU bug report logs -
#20887
'make bootstrap' now verrrry slow due to recent isearch changes
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Reported by: Paul Eggert <eggert <at> cs.ucla.edu>
Date: Wed, 24 Jun 2015 01:36:01 UTC
Severity: normal
Done: Paul Eggert <eggert <at> cs.ucla.edu>
Bug is archived. No further changes may be made.
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> Date: Thu, 25 Jun 2015 18:32:51 +0100
> From: Artur Malabarba <bruce.connor.am <at> gmail.com>
> Cc: 20887 <at> debbugs.gnu.org
>
> I'm aware I could run a loop inside the lambda going from (car key) to
> (cdr key), and then do the `(funcall func ...)' on each item in the
> range, but I fail to see how that would be faster than running a
> second map-char-table. In fact, the number of steps involved is much
> larger if you loop:
> - the current version has a map of 100 steps and another of 5721,
> - your proposal would have a map of 100 steps, each containing a loop
> of about 120 steps, which totals to over 12000 steps (I counted).
>
> Again, maybe I'm missing something, or maybe looping would be much
> faster than that second `map-char-table', but it seems to me like it
> would just be doing more work.
It's not faster, but it's not slower, either. Looping is not what
takes time here, and if you think map-char-table can somehow magically
avoid any looping, you should look at its implementation.
What takes time here is map-char-table itself and the body of the
loop, where the data is processed.
For the record, I show the variant I had in mind below. I timed it on
my system, and found it delivering the same speed as your version, up
to the system clock accuracy.
(defconst character-fold-table
(eval-when-compile
(let* ((equiv (make-char-table 'character-fold-table))
(table (unicode-property-table-internal 'decomposition))
(func (char-table-extra-slot table 1)))
;; Compile a list of all complex characters that each simple
;; character should match.
(map-char-table
(lambda (i dec)
(when (consp i))
(let ((ifirst (car i))
(ilast (cdr i)))
;; Ensure the table is populated for this range.
(funcall func ifirst dec table)
;; Loop over all non-trivial decompositions in the range.
(while (<= ifirst ilast)
(setq dec (funcall func ifirst (aref table ifirst) table))
(or (not (consp dec))
(and (eq ifirst (car dec))
(null (cdr dec)))
(progn
;; Discard a possible formatting tag.
(when (symbolp (car dec))
(setq dec (cdr dec)))
(let ((d dec) k found multiletter)
(while (and d (not found))
(setq k (pop d))
;; Is k a number or letter, per unicode standard?
(setq found
(memq (get-char-code-property k 'general-category)
'(Lu Ll Lt Lm Lo Nd Nl No))))
(if found
;; Check if the decomposition has more than
;; one letter, because then we don't want
;; the first letter to match the
;; decomposition.
(dolist (k d)
(when (memq
(get-char-code-property k 'general-category)
'(Lu Ll Lt Lm Lo Nd Nl No))
(setq multiletter t)))
;; If there's no number or letter on the
;; decomposition, take the first character in it.
(setq found (car-safe dec)))
;; Add i to the list of characters that k can
;; represent. Also possibly add its
;; decomposition, so we can match multi-char
;; representations like (format "a%c" 769)
(when (and found (not (eq ifirst k)))
(let ((chars (cons (char-to-string ifirst)
(aref equiv k))))
(aset equiv k
(if multiletter chars
(cons (apply #'string dec) chars))))))))
(setq ifirst (1+ ifirst)))))
table)
;; Convert the lists of characters we compiled into regexps.
(map-char-table
(lambda (i v) (let ((re (regexp-opt (cons (char-to-string i) v))))
(if (consp i)
(set-char-table-range equiv i re)
(aset equiv i re))))
equiv)
equiv))
"Used for folding characters of the same group during search.")
This bug report was last modified 9 years and 334 days ago.
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