Re: [Boost-users] boost.xpressive is inefficient while seachinginraw bytes

From: Robert Ramey (ramey_at_[hidden])
Date: 2008-01-28 21:15:29

I have sort of a dumb question about this.  What would be the motivation for 
using Xpressive if its not faster than regex?  Putting it another way, I 
would have thought that Xpressive would be faster with the cost of more code 
being instantiated every time it's invoked. What else is going on here? 
Another question: How would using expressive be different than using spirit 
with a regular expression grammar?

I have no purpose for asking other than idle curiosity.

Robert Ramey

Eric Niebler wrote:
> John Maddock wrote:
>> Eric Niebler wrote:
>>>> Boost.regex: 6.859
>>>> Boost.xpressive (dynamic): 3.02
>>>> Boost.xpressive (static): 2.912
>>>>
>>>> With boost.regex, I couldn't use an independent subexpression
>>>> because it disables the optimization. That accounts for the
>>>> difference.
>>
>> I've just extended the optimization to more cases in Boost.Regex (SVN
>>  Trunk), so the two libraries should be back on a par now performance
>>  wise (I hope!)
>
> Confirmed, nice work. <tips hat>