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Subject: Re: [boost] [regex, xpressive] interesting(?) perf benchmark
From: Joel de Guzman (joel_at_[hidden])
Date: 2010-06-07 20:01:11

On 6/8/10 12:10 AM, Eric Niebler wrote:
> On 6/7/2010 9:20 AM, Mathias Gaunard wrote:
>> Eric Niebler wrote:
>>> On 6/7/2010 5:50 AM, Mathias Gaunard wrote:
>>>> Le 07/06/2010 04:58, Eric Niebler wrote:
>>>>> I'm always suspect of benchmarks, but I figured I'd post this anyway.
>>> <snip>
>>>> Just an idea: for static xpressive, couldn't you detect at compile-time
>>>> that the expression is truly regular, and use a DFA in that case?
>>> Oh, sure! Why don't you submit a DFA and I'll use it in xpressive? ;-)
>> How about a warning "you may not be using the optimal tool for the job"
>> until then?
> I'm having a hard time getting excited about that.
>> Are the finite state machine libraries in Boost usable for this at all?
> I don't know. At BoostCon, Christophe presented some interesting results
> pitting MSM against xpressive for some simple regexing. An interesting
> research project would be to investigate whether xpressive's hybrid
> static/dynamic NFA design can be applied to DFAs as well, with similar
> perf wins. This would be a non-trivial undertaking, like completely
> reimplementing xpressive.

Just to remind you, there's a very good DFA implementation underneath
Spirit Lex. The interface is not perfect (Ben has requested for some
input in that area), but the implementation is very good. Spirit Lex
is proto on top of lexertl (Ben's work). We find it to be one of the
fastest lexer, close to performance to the fastest (RE2C) which is a
code-gen that generates a humongous switch.


Joel de Guzman

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