Thanks On Thu, Mar 31, 2005 at 05:16:25PM -0500, Matt Kettler wrote: > Rocky Olsen wrote: > > >Before i pull my hair out doing bench/resource test, i was wondering if > >anyone out there knew if there was much of a speed/resource usage > >difference between the following way of writing the same rule. > > > > > >Method A: > >body rule_a /(?:feh|meh|bleh)/i > > > >vs. > > > >Method B: > > > >bod __rule_a /(?:feh)/i > >body __rule_b /(?:meh)/i > >body __rule_c /(?:bleh)/i > > > >meta rule_d (__rule_a || __rule_b || __rule_c) > > > > > >There probably isn't much difference using just 3 rules, but i'm thinking > >more along the lines of large(500+) lists and it isn't limited to just body > >stuff. So if anyone has some realworld benching/experience with what is > >preferred or if the developers know which is faster for SA, i would love > >the input. > > > > > > To start with, use perl's regex debugger as your friend: > > $perl -Mre=debug -e "/(?:feh|meh|bleh)/i" > size 11 Got 92 bytes for offset annotations. > > $ perl -Mre=debug -e "/(?:feh)/i" > Freeing REx: `","' > Compiling REx `(?:feh)' > size 3 Got 28 bytes for offset annotations. > > (repeat 2 times) > > However, this only deals with part of the story. The cost of the regex > itself. It does not deal with the per-rule overhead in SA. > > In general I'd favor the combined approach, unless for some reason your > combined rule is considerably larger than the sum of it's parts. Bigevil > ran much better once Chris S did some combining and common subexpression > elimination. > > > > > Also, I'd suggest eliminating the (?:) for the single-text-matches. It > does nothing of use, and doesn't change the evaluation of the regex any > for a simple single text match. All it does is waste 4 bytes of disk > space per rule. > > body __RULE_A /feh/i > > instead of: > body __RULE_A /(?:feh)/i > > I leave comparing the two using re=debug as an exercise for the student. > Also compare to /(feh)/i and /(feh)\1/i to see how backtracking works. > > > > > > >
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