Subject: Re: bug#16800: 24.3; flyspell works slow on very short words at the end of big file

From: Aleksey Cherepanov <[email-masked]>
Date: Sun, 23 Feb 2014 23:56:59 +0400

On Sun, Feb 23, 2014 at 02:26:00AM +0100, Agustin Martin wrote:
> 2014-02-22 22:03 GMT+01:00 Eli Zaretskii <[email-masked]>:
> 
> > > Date: Sat, 22 Feb 2014 22:55:11 +0400
> > > From: Aleksey Cherepanov <[email-masked]>
> > >
> > > > > Emacs words are language sensitive too.
> > > >
> > > > But not in the same way as ispell/flyspell is.  The CASECHARS,
> > > > NON-CASECHARS, and OTHERCHARS parameters of the dictionary are only
> > > > taken into account by ispell/flyspell.
> > >
> > > I think one could define a dictionary like: ("my" "[a]" "[^a]" "" ...)
> > > So the only letter for flyspell words is "a". That way "qqaaqqaaqq" is
> > > one word for emacs and two words with garbage around for flyspell. I
> > > think my solution fails in such case.
> >
> > It's more complex than that: with some languages, and at least with
> > aspell, we take these parameters from the dictionary.  So they cannot
> > be known in advance in some cases.
> >
> 
> Hi,
> 
> Not yet sure if  I am missing something important, but I am playing with a
> regexp search in flyspell-word-search-* functions based on what flyspell
> thinks is the word to spellcheck (`word') and what thinks should not be
> part of a word (`NOTCASECHARS'). Since no OTHERCHARS is used there may be
> some intermediate matches being false positives that will be discarded once
> flyspell-word checks them.
> 
> I have tested this in Alekseys's file and is apparently working well and in
> this particular case with much better efficiency. Need to think about more
> ad-hoc situations where it may fail or slow down things. Suggestions for
> possible failures are welcome.
> 
> Patch is attached. I did the tests against an old and patched version of
> flyspell.el (that shipped with Debian stable) and built the patch for it.
> Should apply and work similarly in trunk's flyspell.el.
> 

> --- flyspell.el.orig	2014-02-23 02:17:03.680107519 +0100
> +++ flyspell.el	2014-02-23 02:50:50.634625248 +0100
> @@ -1050,8 +1050,19 @@
>    (save-excursion
>      (let ((r '())
>  	  (inhibit-point-motion-hooks t)
> +	  (flyspell-not-casechars (flyspell-get-not-casechars))

I'd move concat here too so it is out of inner loop.

>  	  p)
> -      (while (and (not r) (setq p (search-backward word bound t)))
> +      (while 
> +	  (and (not r) 
> +	       (setq p 
> +		     (re-search-backward
> +		      (concat
> +		       "\\(" flyspell-not-casechars "\\|\\b\\)"

I think \b here could be replaced with \` (beginning of buffer). I
think it is the only boundary we need that is not described by
not-casechars, word sequence. Similarly \' (end of buffer) could be
used for forward search.

Also not capturing group ("\\(?:") could be used because we do not
need a match data of the first group. It should work faster but I
don't really know.

Maybe it would be faster to not capture word but capture one char or
void but I doubt the difference would be noticable.

> +		       "\\(" word "\\)"

I think regexp-quote around the word is necessary here.

> +		       flyspell-not-casechars
> +		       )
> +		      bound t)))
> +	(goto-char (match-beginning 2))

s/2/1/ if the first group is not capturing.

>  	(let ((lw (flyspell-get-word)))
>  	  (if (and (consp lw)
>  		   (if ignore-case
> @@ -1068,8 +1079,19 @@
>    (save-excursion
>      (let ((r '())
>  	  (inhibit-point-motion-hooks t)
> +	  (flyspell-not-casechars (flyspell-get-not-casechars))

concat here as above.

>  	  p)
> -      (while (and (not r) (setq p (search-forward word bound t)))
> +      (while 
> +	  (and (not r) 
> +	       (setq p 
> +		     (re-search-forward 
> +		      (concat
> +		       flyspell-not-casechars
> +		       "\\(" word "\\)"

regexp-quote as above.

> +		       "\\(" flyspell-not-casechars "\\|\\b\\)"

I think \b could be replaced by \' here as described above.

The second group could be not capturing here.

> +		       )
> +		      bound t)))
> +	(goto-char (match-beginning 1))

I guess match-end should here.

>  	(let ((lw (flyspell-get-word)))
>  	  (if (and (consp lw) (string-equal (car lw) word))
>  	      (setq r p)

I guess that \b would work faster than the group so we could have 'if'
statement around the whole loop that has one implementation with \b
for case when casechars are "[[:alpha:]]" and not-casechars are
"[^[:alpha:]]" and another implementation as above for other cases.
But it seems cumbersome.

Thanks!

-- 
Regards,
Aleksey Cherepanov