Daniel Naber <daniel.na...@languagetool.org> wrote:
> Hi,
>
> there's a regex that makes tests quite slow in PatternTestTools.java:
>
> CHAR_SET_PATTERN =
> Pattern.compile("(\\(\\?-i\\))?.*(?<!\\\\)\\[^?([^\\]]+)\\]")
>
> I don't fully understand it, does it need to be that complicated? If I
> simplify it like this:
>
> CHAR_SET_PATTERN = Pattern.compile("\\[^?([^\\]]+)\\]");
>
> The tests become much faster (45 second -> 8 seconds for Polish when
> running just the disambiguation tests).
>
> Regards
> Daniel
Hi Daniel
I have not had the time to look at what this regexp is used for,
but glancing at the regexp, I see that it contains a zero-width negative
lookbehind, i.e. the (?<!…) part. This can be very slow I slow I think.
At least in Vim, regexp, zero-with lookbehind are documented as very
slow (see :help \@<! in Vim). I suspect that it's the same for other
regexp engines. Perhaps the regexp can be written in such a way to
avoid the zero-width lookbehind.
Regards
Dominique
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