[Boost-users] build times and Boost.MultiIndex 2

From: gast128 (gast128_at_[hidden])
Date: 2008-06-05 10:34:30

 <joaquin <at> tid.es> writes:

> 
> gast128 escribió:
> > Dear all,
> >
> > just refactored a component in our (large) application with use of
> > Boost.MultiIndex. However using a test application it seems that by only
> > including the Boost.MultiIndex header in the header files, the build time 
is 7
> > times (700%) slower than without that header file.
> >
> > Pulling Boost.MultiIndex to the cpp file is no option, because I need to
> > export the iterator as well. Of course I can make a wrapper around the
> > iterator as well (for the sole purpose to shield the inclusion of the
> > Boost.MultiIndex header), but isn't this a little bit strange? Putting
> > Boost.MultiIndex in the pch is also a no-op because, 1) every pch must be
> > adjusted, 2) VC++ 7.1 chokes on that.
> >   
> 
> I'm sorry to hear that. B.MI is certainly a template intensive library 
> and this is the price
> one has to pay to use it. PCHs should really be the approach to use, as 
> improvements
> are generally dramatic. If globally changing PCHs is not acceptable 
> maybe you can have a
> testing mode in your app that has B.MI included in PCHs, even if this is 
> not the configuration
> for final builds.
Well I tried, but I got a rare unrelated compile error in the middle of an STL 
header. Mostly they are then related to out of memory conditions or crashes 
within the compiler. Btw, we already have a crowded pch file (with STL, 
iostream, some boost libraries etc.).

> 
> Regarding the advice given by Ovanes in a previous post, I'm afraid you 
> probably can't 
> get by using the forward header, as this does not define B.MI iterators. 
I saw the file and it didn't specify the iterators.

> Another option is
> to use pointers instead of iterators in your public interface so that 
> you can move the
> B.MI headers to the cpp file; version 1.35 of B.MI provides a member 
> function
> called iterator_to that allows you to pass from pointers to iterators:
> 
> http://www.boost.org/libs/multi_index/doc/tutorial/indices.html#iterator_to
Thx, but I need the iterators for ...iteration. I can also swith back to 
std::map (or std::set); the use case here is to sort a container of 
(shared_ptrs of) objects on a member key. Using std::map or std::set is then 
either redundant or one get difficulties with key search (by using a dummy 
variable), just as specified in the documentation.
 
> I think this a quality of implementation issue that the commitee can't 
> do much about.
> Template metaprogramming is an accidental use of templates so generally 
> compilers
> are not ideally suited to the heavy compile time activity it generates. 
> Hopefully things
> are improving on this area largely due to the influence of Boost.
I hope so too. The test program didn't use any Boost.MultiIndex: it had only 
the header files. Wouldn't it be possible in someway to optimize that (but I 
am not a compiler guru), by skipping extensive parsing of the header file?

wkr, 
me