Re: [boost] [xpressive] Performance Tuning?

Subject: Re: [boost] [xpressive] Performance Tuning?
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2009-07-28 08:39:24

OvermindDL1 wrote:
>
> I did a quick first test at work, just a quick compile, got some
> errors, and quite frankly I do not know how this compiled in gcc
> either.  First error is:
> 1>r:\programming_projects\spirit_price\price_parsing\main.cpp(545) :
> error C2373: '_input' : redefinition; different type modifiers
> 1>
> r:\programming_projects\spirit_price\price_parsing\main.cpp(544)
> : see declaration of '_input'
>
> The relevant code is:
>    template <class T>
>    T
>    extract(char const * & _input, char const * _description,
>       std::string const & _input);

That was just a copy paste error in a declaration.  GCC 4.1.2 didn't complain about it for me and I have warnings up very high.  You can remove the formal parameter names, if you like.

> Why do the first and last function params have the same name (_input)?
>  And which one is the real input?  Based upon line 566, I changed the
> last _input to _value and that error (and one other) is now gone.

Yes, the third argument is _value.

> Hmm, actually the third error is gone too.  Now I am getting lots of
> Warnings (as errors since I by default have warnings treated as
> errors) about double to int64_t cast, both in  your normal code on
> line 730

I don't know where you're seeing those warnings.  I've addressed all such warnings I get from GCC 4.1.2.  My warnings are set to "-Wall -Wno-comment -Wpointer-arith -W -Wconversion -Wno-long-long."

> Also, I added a:
>    tests.reserve(450000);
> right before the load_tests call, that changed the load_tests time
> from like 10 seconds to about 2 seconds on my system.

You're assuming the full set of test inputs.  I was allowing for testing with reduced input sets.  You could read the file twice to count the number of lines and then reserve enough elements to maintain flexibility and, possible, improve performance.  However, that's done once before running all of the tests, so I certainly didn't worry about the performance of that initialization.

> Also, why are you using time(0), that only has second accuracy?

It is simple and portable.

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer, Core Software      using std::disclaimer;
Susquehanna International Group, LLP  http://www.sig.com

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