Re: [boost] Enabling fast swap optimization for Boost types VC9 SP1.

From: Niels Dekker - mail address until 2008-12-31 (nd_mail_address_valid_until_2008-12-31_at_[hidden])
Date: 2008-08-26 12:29:16

Michael Marcin wrote:
> I think the only real way to get it right in every case is
> to have the author of the type specify the proper traits.

Okay, I give up. A generic way to tweak MSVC's "Swaptimization" just 
doesn't seem feasable without adding a /lot/ of template 
specializations.

See also the reply by Stephan T. Lavavej on my questions at
http://blogs.msdn.com/vcblog/archive/2008/08/11/tr1-fixes-in-vc9-sp1.aspx

So any type for which default-construction + swap outperforms 
copy-construction should preferably have "Swaptimization" enabled. 
Let's call such a type "Swaptimizable". So should we add a 
specialization of std::_Move_operation_category to each Boost HPP file 
that defines a "Swaptimizable" type?  Or would it be preferable to have 
a single header file, containing std::_Move_operation_category 
specializations of for all "Swaptimizable" Boost types?

Note that for some templates whether an instantiation is "Swaptimizable" 
depends upon its template argument.  For example, "Swaptimization" 
should be applied to boost::array<std::string>, but not to 
boost::array<int>.

Kind regards, Niels