Re: [boost] Question about optimizations in Boost.Regex

From: John Maddock (john_at_[hidden])
Date: 2008-04-16 04:45:07

Sam Jiang wrote:
> Hi All
>
> I'm just wondering; what kind of optimizations does the regex library
> come with?
> i.e if I was to say ^(string1|string2|string3), does it result in same
> performance as using ^string[123]?

No not currently - actually I don't know of any Perl-Regex libraries that do 
that at present (but may well be wrong).

Most of the optimisations relate to:

* Skipping over text that can't possibly match in a small tight loop when 
searching large texts.
* Pruning the search tree as aggressively as possible, to avoid the Perl 
Regex O(N!) worst case behaviour where possible.

HTH, John.