Re: replace regex takes long

[Gary Wessle <phddas@yahoo.com>]

Eli Zaretskii <eliz@gnu.org> writes:

> > From: Gary Wessle <phddas@yahoo.com>
> > Date: 16 Apr 2006 09:35:00 +1000
> > 
> > Gary Wessle <phddas@yahoo.com> writes:
> > 
> > > Peter Dyballa <Peter_Dyballa@Web.DE> writes:
> > > 
> > > > Am 15.04.2006 um 23:29 schrieb Gary Wessle:
> > > > 
> > > > > M-x query-replace-regex <RET> +<RET><ONE SPACE>
> > > > > the file size is 4162111 with 77000 lines on PentiumIII 500, it has
> > > > > been 10 minutes so I opened another emacs processor to write and
> > > > > post this.
> > > > > is there a problem with my command and why it is taking that long?
> > > > 
> > > > Yes, because the command needs your co-operation. And if you don't
> > > > press "yes" no change will be made.
> > > 
> > > if fact I forget to say that I did hit ! which means "replace all"
> > with M-x regex-replace it shows (replaced 304172 occurrences) and it
> > is taking more than 5 minutes now and still have not finished the
> > task.
> 
> I just tried query-replace-regex on a file with the structure you
> described, and the command ran to completion in just 40 seconds,
> including 3 questions whether to discard undo info.  That was on a
> 3-GHz Pentium 4 in a buffer that is in Fundamental mode.  So your
> timing seems very unusual, to say the least.
> 
> Do you have some specialized major mode in that buffer?  If so,
> perhaps it slows down the replacement; try in Fundamental mode.  I'd
> also suggest to try the command in "emacs -q", perhaps something in
> your customizations slows down the replacements.
> 
> In any case, your command is wasteful because it forces Emacs to
> replace even a single space.  I suggest to try this instead:
> 
>     M-x query-replace-regex <RET>  +<RET> <RET>
>                                  ^^
>                              two spaces here
> 
> This command takes just 20 seconds on my machine.
> 
> Btw, what version of Emacs do you have, and on which OS?

I did it as you described, 
#emacs -q
M-x query-replace-regex<RET>  +<RET> <RET>
it took 24 sec. my OS is debian testing and
emacs version 21.4.1

thanks