Eric Niebler wrote:
Sebastian Redl wrote: <snip>
http://www.linux-magazin.de/static/listings/magazin/2008/10/leser/cpp/footno...
<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
Has anyone done a proper performance comparison between Xpressive and libpcre?
Not really, no. I may look into this, if it doesn't turn out to be a simple matter of compiler optimization. Where can I find the input file you're testing with? http://www.linux-magazin.de/static/listings/magazin/2008/10/sprachen/ It's the sample4.txt.bz2. (8MB, expands to 55MB)
Thanks for looking into this. Sebastian