Re: parallel make help

[Bob Friesenhahn]

On Thu, 10 Apr 2008, Ralf Wildenhues wrote:
> I've thought of this, in fact just a couple of weeks ago.  It is
> possible to formulate SUBDIRS rules in a way that allows parallel
> execution of the sub makes (by something like turning each subdir
> into a target).  However, doing so by default will certainly break
> lots of existing setups.  That's why my current thinking is that
> it may be possible to introduce a new feature, say,
>  PARALLEL_SUBDIRS = ...
>
> which would then show automake that these subdirectories really
> can do work in parallel.  Maybe even get this functionality turned
> on per-project with an automake option, dunno yet.

The problem is that existing projects using SUBDIRS absolutely depend 
on each directory being completely processed before moving on to the 
next one since there is no dependency information outside of 
subdirectories.  The only way to resolve this is by adding additional 
dependency knowledge, and you soon end up with everything needed for a 
non-recursive build. :-)

Setting up a non-recursive build project with Automake would not be 
such a chore if Automake knew how to ingest per-subdirectory Makefiles 
into the overall build, adding any necessary path information.  The 
biggest chore related to setting up a non-recursive build is that all 
of the paths need to be completely specified (from the top), but 
modified to work with Automake.

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