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Re: Faster compilation speed


--- Ziemowit Laski <zlaski@apple.com> wrote:
> 
> On Friday, August 9, 2002, at 03:12 , Stan Shebs
> wrote:
> 
> > Noel Yap wrote:
> >
> >> Build speeds are most helped by minimizing the
> number
> >> of files opened and closed during the build.
> >>
> > Is this assertion based on empirical measurement,
> and if so, for what
> > source code and what system?  For instance, the
> longest source file
> > in GCC is about 15K lines, and at -O2, only a
> small percentage of
> > time is spent messing with files.  If I use
> -save-temps on cp/decl.c on
> > one of my (Linux) machines, I get a total time of
> about 38 sec from
> > source to asm.  If I just compile decl.i, it's
> about 37 sec, so that's
> > 1 sec for *all* preprocessing, including all file
> opening/closing.
> 
> Since the preprocessor is integrated, I don't think
> you can separate
> the timings in this way. :(  A 'gcc3 -E cp/decl.c -o
> decl.i' would
> probably be more meaningful.

This is a good point.

I think an even better study would be to replicate
John Lakos's study within one's own project.  I'd be
very interested to find out how many projects (other
than the ones I've seen) fit Lakos's "largeness" and
would, therefore, be able to take advantage of
preprocessed headers.

Noel

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