On 19 July 2013, Mike Williams <mike.willi...@globalgraphics.com> wrote:
> On 19/07/2013 15:52, Mike Williams wrote:
> >On 19/07/2013 12:18, Dimitar DIMITROV wrote:
> >>Hi,
> >>
> >>Did a search on the vim_dev archives but couldn't find anything
> >>related to this. Sorry if this is redundant. Basically vim is
> >>exponentially slow after 1000000iHello <esc> as mentionned in this
> >>link:
> >>http://www.galexander.org/vim_sucks.html
> >
> >A quick run over with a profiler seems to show most of the time is
> >being spent in vim_strchr() called from has_format_option(), called
> >from internal_format(). If I first do :set paste then it is a lot
> >quicker - for 4000iHello<ESC> it goes from 16s down to 1s.
[...]
> Textwidth. Darn sight quicker with it set to 0, wish I had
> remembered that. Another factor of ~2 quicker for my final times,
> 16000iHello<ESC> now takes ~4s.
[...]
Right, what you're seeing here is Vim backtracking to find a blank
to split that N * "Hello" line. Since there is no such blank, you get
len("Hello") * N * (N + 1) / 2 failed comparisons, which is exactly the
O(N^2) behaviour claimed in the article mentioned above.
If you replace your test by, say, "16000iHello <ESC>" (with a space
after "Hello"), you get linear behaviour, namely len("Hello") * N failed
comparisons.
I believe this can be fixed with a counter that means something
along the lines of: "this line is longer than &tw, and it has no
breaking point for the first X characters". Then X would be updated
every time more text is appended to that line.
On 19 July 2013, Marc Weber <marco-owe...@gmx.de> wrote:
> Let's discuss the use case, first. Is there one ?
Yes, there is: you run through that piece of code every time you
press "p" to paste text. It hits you particularly hard when you edit
files with very long lines.
> If not let's forgett about it ..
[...]
Perhaps we should try to understand the problem before dismissing it
as harmless?
/lcd
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