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Subject: Re: [boost] [xpressive] Performance Tuning?
From: Edward Grace (ej.grace_at_[hidden])
Date: 2009-07-19 07:27:52

> 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++.

Dear Joel,

Would you mind trying out these examples with my timer? I'd like to
see if it gives sensible answers for other people's code on other
people's machines. Attached is a reworking of your testbed code
using my timer which can be obtained from boost vault,

I haven't been able to try compiling the attached modification to
your code myself as I don't have the boost spirit libraries. Even if
I did it still wouldn't be your machine! Since I can't compile it
there *will* be some errors! The ugly global variables are sadly an
unavoidable side effect at the moment.

I have pared down the number of iterations quite significantly. The
generic_timer makes repeated calls to the functions under test - as
many as necessary to 'get the job done' - so there's no need to have
large run-times in order to effectively get an average time.



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