[boost] Re: new compile-time dimensional analysis and unitlibrary

From: David Abrahams (dave_at_[hidden])
Date: 2003-12-20 16:31:30

"Andy Little" <andy_at_[hidden]> writes:

> "Matthias Schabel" <boost_at_[hidden]> wrote in message
> news:3088ED01-319D-11D8-B491-000393DC6706_at_schabel-family.org...
>
>
>> suggestions on improving performance.  I am a little puzzled that
>> Mr.  Little is suddenly so fixated on compile-time performance
>
> Hi Mattihas :-)
>
> One of the major problems with Anyones heavy use of MPL is, as I
> understand, its compile time performance.  I cant remember the
> references but this is mentioned ..."compile time is a precious
> resource when using MPL" or something similar I think in the MPL
> leaflet on the files section. 

Compile time is a precious resource when doing any metaprogramming.
In fact using MPL can effectively reduce compilation times over ad-hoc
metaprogramming techniques, because optimizations have been applied to
various parts of the library... but whether it will be faster or
slower is still dependent on the problem being solved and your
approach to it.

> It is also mentioned in my Templates the complete guide book
> Vandevoord & Josuttis I am waiting for David Abrahams book to come
> out. I am sure there will be some useful info on the subject in it.

Yes.

> Dont get me wrong MPL is an important subject and the consensus
> appears to be that you have made a good start.  But there is a point
> where compile times severely affect the way I code.  It is no fun
> and expensive having to work with slow compile times.

I'm not sure from the above (and especially your mention of
Vandevoorde & Josuttis, which doesn't discuss the MPL) whether you're
talking about MPL itself or any metaprogramming at all.  Do you have
an a priori reason to think that using the MPL is going to make
compilation times longer than doing it some other way?

> (If people bang on about it the MPL guys may take notice... ;-) )

Do you think Aleksey and I haven't given compilation time a lot of
attention already?

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com