Dave Jenkins wrote:
Robert Stuart wrote:
Whoa! The performance just shot up to a mere 6X the custom code (from 175X). That might well be fast enough to keep the Xpressive version because of its readability!
Can you create thread-local match_results objects and reuse them? If so, I think you'll see parsing dwindle to almost nothing and your semantic actions will account for the bulk of the time spent.
Dave, thanks for spotting the obvious perf problem I missed. I can confirm that reusing the match results object largely eliminates the remaining performance problem. I tried 3 different scenarios: 1) The original code 2) Static const regexes 3) Static const regexes with reused match results objects I ran each config for 1000000 iterations and got roughly these numbers: 1) ~950 sec 2) ~45 sec 3) ~9 sec So reusing the match results object (3) results in a 5x speedup over just using static const regexes (2). That almost completely erases any performance advantage of the hand-crafted parsing code. I'll also point out this section of the docs: http://www.boost.org/doc/libs/1_39_0/doc/html/xpressive/user_s_guide.html#bo... Both of the above optimizations (reuse regexes and match_results objects) are recommended there. Thanks, -- Eric Niebler BoostPro Computing http://www.boostpro.com