Re: [Automake-NG] Idea: Inverse sort re-builds by time

[Stefano Lattarini]

Hi Bob, sorry for the delay.

On 08/31/2012 09:21 PM, Bob Friesenhahn wrote:
> Given the mention of 'sort' in another thread, I would like to mention
> something that I have thought about for some time.  When one does
> parallel builds on systems with many cores (particularly slow cores),
> the time to complete a build is improved if build products which take
> a long time are done first and ones which complete quickly are done
> last.  Most importantly, a really slow compilation/link should not
> be scheduled last if at all possible.  The reason for this is that
> all other objects may have already been compiled while one or two
> last objects which are slow to compile or link are still completing.
> Linking may be I/O bound and take a long time while leaving plenty
> of CPU for other compilations.
> 
> The thought is that if the time to build each component is captured
> and saved, then subsequent builds can be done in inverse order of
> build times (by listing them in that order), subject to build
> dependencies.  This could even be codified in the makefiles in the
> distribution tarball.
>
> The benefits would be greatest for non-recursive builds where all
> of the targets may be scheduled at once (modified by explicit
> dependencies) by one make process.
> 
> The maximum possible benefit would be determined by the slowest
> build product (if it had been scheduled to start last).
> 
> Thoughts?
>
I think that such a feature would be better implemented in GNU make
rather than in Automake-NG (or any other kind of make pre-processor).
Have you tried to write to the GNU make list to see their reaction
and feedback?

Regards,
  Stefano