Re: Analyzing regular expression performance

This is an archived low-energy page for bots and other anonmyous visitors. Please sign up if you are a human and want to interact.

to analyse a regex, you can use YAPE::Regex::Explain.

update: one example: perl -MYAPE::Regex::Explain -e 'print YAPE::Regex::Explain->new(qr/(<a\s(?:[^>](?!href))*href\s*)(&(&[^;]+;)?(?:.(?!\3))+(?:\3)?)([^>]+>)/)->explain'

For the performance, one thing that comes to my mind is the /o qualifier to compile once only. And if You still suffer from perfomance issues, You might want to use a debugger and/or profiler. But in that case, maybe You should first try to 'divide and conquer' the regexp into a few smaller ones.

Comment on Re: Analyzing regular expression performance Select or Download Code

Replies are listed 'Best First'.
Re^2: Analyzing regular expression performance by duff (Parson) on May 12, 2006 at 14:37 UTC
For the performance, one thing that comes to my mind is the /o qualifier to compile once only Yikes! Don't ever recommend that. It's rarely needed and causes more trouble than it is worth. Perl already does optimizations for patterns that contain no variables and for patterns that do contain variables that don't vary over the lifetime of the code in which the pattern appears, so `/o` won't buy you anything there. If you really need the "compile once" idea, just use `qr/.../` duff	[reply] [d/l] [select]
Re^3: Analyzing regular expression performance by mantadin (Beadle) on May 12, 2006 at 18:51 UTC
what You say makes sense to me. At least the 'wont buy you anything' part. What I dont understand: how can the /o cause trouble?	[reply]
Re^4: Analyzing regular expression performance by duff (Parson) on May 13, 2006 at 00:32 UTC
See this node duff	[reply]

• hippo

‥ epoptai's answer Re: how do I set a cookie and redirect was blessed by hippo!

• erzuuli

‥ Anonymous Monks are no longer allowed to use Super Search, due to an excessive use of this resource by robots.


Pathologically Eclectic Rubbish Lister
	PerlMonks