Re: parallelized configure

[Bob Friesenhahn]

On Wed, 15 Jan 2014, Alexander Holler wrote:
> Sure, people do all kind of stuff in build systems. But a lot of tests
> which do fly by when configure is called do look like taken from a
> standard repository. And many of those tests are pretty simple and
> without any dependencies.

It seems that all tests have dependencies.  What tests do you think 
don't have any dependencies?  If I specify CC on the configure command 
line, that may influence the outcome and demonstrates that there are 
dependencies.

> Hmm, I'm using the parallel feature from gnu make very successful since
> ext4 with support for nanosecond timestamps appeared (so since many
> years). Without a fs with high resolution timestamps I had a lot of
> problems, but with high resolution timestamps it works most of the time
> like a charm.

This is perhaps off-topic for the Autoconf list.  Packages with a lot 
of recursion and less than 64 target object files per directory, or 
with some targets which take substantially more time than other 
targets to compile, do not perform as well as they should for parallel 
builds on modern CPUs (with 4-64 cores available).  If the object 
files compile very quickly, then there is also less gain from parallel 
builds since the build framework may take more time than the actual 
compiles.  Lastly, if there are many linking steps, the build time is 
dramatically increased since linking is sequential in nature, and if 
there is needless re-linking (a common problem with recursive builds) 
then the problem is multiplied.

Bob
--
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/