Hi, A German journal recently published a small programming contest with a very simple text processing problem. The program needs to renumber and sort footnotes in a long text. I wrote a solution in C++ using a number of Boost libraries, among them Xpressive, but also Interprocess for memory-mapping the input file. Then I looked at the submissions page and found one C++ solution already there, an admirably short (but rather inflexible) program using libpcre. http://www.linux-magazin.de/static/listings/magazin/2008/10/leser/cpp/footno... Comparing the performance, my program was sightly but consistently slower than this small program, even when I felt that my usage of memory-mapping and then scanning the whole file instead of going line by line ought to give me a speed advantage. 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. Has anyone done a proper performance comparison between Xpressive and libpcre? Boost.Regex's performance pages lists PCRE, but in version 4.1, where 7.8 is the most recent release. My system: Athlon 64 2000MHz (64-bit mode) 1GB RAM Linux 2.6.23, GCC 4.1.2 Boost trunk as of 2008-09-11 libpcre 7.7 Sebastian Redl