Re: [Boost-users] boost.regex vs perl

From: Jeff Garland (jeff_at_[hidden])
Date: 2007-11-22 10:44:34

John Maddock wrote:
> Jin Sun wrote:
>> Can anybody tell me which one has better performance?
> 
> Well it depends what you mean :-)
> 
> I'd be surprised if there was much difference between the core regex 
> engines: maybe one would be slightly better at some things the other at 
> different things.  Where you gain with Boost.Regex is in the ability to 
> write the surrounding code in a compiled language rather than have it 
> interpreted.  Whether you succeed in making your app faster as a result will 
> mainly depend on how cunning you are at avoiding unnecessary copying/memory 
> allocations in your code logic: to put it another way, badly written C++ can 
> be the slowest thing around, while well written code can be as fast as any 
> language out there.
> 
> Oh, and not all regular expressions are created equal: if the problem is the 
> speed of the regex matching, then it's likely a problem with the regex 
> you're using.
> 
> Just my - entirely biased - 2c, John Maddock. 

Keeping in mind John's caveats, I find the language shootout website to be an 
interesting way to compare.  Here's a c++ vs perl results:

http://shootout.alioth.debian.org/gp4/benchmark.php?test=all&lang=gpp&lang2=perl

http://shootout.alioth.debian.org/gp4/benchmark.php?test=regexdna&lang=all

The regex-dna test is written using boost-regex and tests out ~2.4 times 
slower and with a larger memory footprint than the perl version.  Note that 
this is the *only* benchmark where perl outperforms c++.

That said, it's one data point and what you're doing may have totally 
different results.  That's not to mention the effect of the compiler -- gcc 
doesn't have a greatest reputation for optimization although it's been 
improving.  And, you're also depending on other programmers to write good 
benchmarks.

Jeff