Re: [boost] [xpressive] Performance Tuning?

Subject: Re: [boost] [xpressive] Performance Tuning?
From: Joel de Guzman (joel_at_[hidden])
Date: 2009-07-19 06:07:25

Joel de Guzman wrote:
> OvermindDL1 wrote:
> 
>> I just changed the file to use spirit for parsing where I had used
>> lexical_cast got very different timings for xpressive now, so now,
>> with xpressive using a bit of spirit I get:
>> Loop count:  10000000
>> Parsing:  42.5
>> xpressive:  15.4841
>> spirit-quick(static):  3.01117
>> spirit-quick_new(threadsafe):  3.10548
>> spirit-grammar(threadsafe/reusable):  3.81694
>>
>> Vast increase, 3x faster xpressive is now.
>> Also, how do you fix that rather bloody massive warning about
>> double->int64 truncation?
>> I also changed all int64_t to boost::long_long_type since they are the
>> same thing anyway (on 32-bit at least?), as well as it being
>> multi-platform unlike int64_t.
>> My changed file is attached.  Do not know if this is considered
>> cheating now that xpressive is using some spirit now.  ;-)
> 
> This is somewhat cheating. We've tuned the numeric parsers of Spirit
> with TMP tricks, loop unrolling, etc. Those are very finely tuned
> numeric parsers you see there that beats the fastest C code such as
> strtol and atoi. The following benchmarks reveal 2X+ speed against
> low level strtol and atoi (attached). I am getting:
> 
>   atoi: 0.82528 [s]
>   strtol: 0.792227 [s]
>   int_: 0.358016 [s]
> 
> The first and second are the low-level C routines. The third is
> Spirit's int_ parser. I need not mention that the C routines only
> accept C strings while the Spirit int_ parser can accept any
> forward iterator. So, in a sense, we're comparing apples and
> oranges. But this goes to show that you can write highly optimized
> code in generic C++.

Oh, BTW, that's MSVC 9, on a Core 2 Duo 2.4 Ghz, 3MB RAM.

Regards,
-- 
Joel de Guzman
http://www.boostpro.com
http://spirit.sf.net