Re: [Boost-users] [Boost.Array] surprising performance issue

From: KSpam (keesling_spam_at_[hidden])
Date: 2007-11-27 10:25:52

Bryan,

> I've discovered a situation where using boost::array results in a
> 2-fold performance degradation over other array types, including C arrays,
> tr1::array, and a simple handwritten array class.
> While the tr1::array performs well, I was suprised to find that it pads the
> array, so sizeof(tr1::array<3,float>) == sizeof(tr1::array<4,float>).  Is
> that a requirement of tr1::array?

It is very strange that you see a performance difference between tr1::array 
and boost::array.  I think that boost::array was used as a submission for 
tr1::array (they are likely one and the same).

> Anyway, the performance problem can be seen using Intel C++ (v9.1) on the
> Itanium platform, using '-O3' optimization.

In your build environment, ensure that you ARE NOT defining _DEBUG, and that 
you ARE defining NDEBUG.  These flags can make a significant difference in 
run-time performance.  Just because you are compiling with optimization flags 
does not necessarily mean you are running the most optimized code :-)

Hope This Helps,
Justin