Re: [Boost-users] [Xpressive] regex-like boost libraries vs re2c

From: Lynn Allan (l_d_allan_at_[hidden])
Date: 2006-04-14 18:59:56

>> Stuart Dootson wrote:
>> Lynn - it might be interesting to use re2c (http://re2c.org/) to
>> generate regex machines and see what their performance is like -
>> after
>> all, they do clain 're2c generates warning free code that is equal
>> to
>> hand-written code in terms of size, speed and quality.' (I'm
>> offering
>> no opinion on the veracity of that statement....), so (allegedly)
>> they'd give a reasonable hand-code analogue....
>
> Lynn Allan wrote:
> I took a look at it, and it looks like it could possibly be quite
> useful if executable size was a concern .... but it is pretty 
> obscure

re2c seems very fast, and once you get the hang of it, not that 
difficult to use. For the contrived test of looking for DayOfWeek 
within a 1kb buffer, here are some results ... ymmv (WinXp-Sp2 
Microsoft ToolKit-2003 C++ Compiler with /O2 optimize flag)

regex = "(Sunday|Sun)|(Monday|Mon) etc.(Saturday|Sat)";

By-hand parser: Elapsed for 10000 loops Ms: 110.583
By-hand parser: Elapsed for 100000 loops Ms: 1107.81

re2c generator Elapsed for 10000 loops Ms: 69.4683
re2c generator Elapsed for 100000 loops Ms: 700.546

Boost::xpressive-static-iterator: Elapsed for 10000 loops Ms: 410.492
Boost::xpressive-static-iterator: Elapsed for 100000 loops Ms: 4164.45

Boost::regex: Elapsed for 10000 loops Ms: 622.377
Boost::regex: Elapsed for 100000 loops Ms: 5965.24