on Sun Sep 14 2008, Sebastian Redl <sebastian.redl-AT-getdesigned.at> wrote:
Eric Niebler wrote:
Sebastian Redl wrote: <snip>
http://www.linux-magazin.de/static/listings/magazin/2008/10/leser/cpp/footnotes.cpp> <snip>
So to test the performance I took the existing submission and replaced libpcre with Xpressive (see attached file). I believe the solutions to be functionally equivalent. However, the original takes 6 seconds to process a 55MB file, whereas my variation takes ~15 seconds. That's on the second run of each program, meaning that the entire file is in the OS cache. This seems awfully slow.
It does seem slow, especially considering all the IO, lexical casting and memory management it's doing, besides the regexing. (I notice that the pcre version isn't doing any lexical casting, but I can't tell if it's doing something equivalent.) It is, by passing a pointer to an int to the matcher functions. libpcre converts internally.
Are you sure you compiled with full optimizations turned on, and NDEBUG defined? I use bjam's release mode. "g++" -ftemplate-depth-128 -O3 -finline-functions -Wno-inline -Wall -fPIC -march=athlon64 -DNDEBUG The other program is compiled with g++ -O2
You should really try them with identical options, as -O3 is known to be worse than -O2 in some cases. -- Dave Abrahams BoostPro Computing http://www.boostpro.com