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

 <joaquin <at>> 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:
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?


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