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Subject:	RE: OT: possible project/research project
Date:	Thu, 21 Mar 2002 22:19:37 +1100
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From:	"Robert Collins" <robert DOT collins AT itdomain DOT com DOT au>
To:	"Jesper Eskilson" <jojo AT virtutech DOT se>, <cygwin AT cygwin DOT com>
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> -----Original Message-----
> From: Jesper Eskilson [mailto:jojo AT virtutech DOT se] 
> Sent: Thursday, March 21, 2002 4:52 PM
> To: cygwin AT cygwin DOT com
> Subject: Re: OT: possible project/research project
> 
> 
> "Gary R. Van Sickle" <g DOT r DOT vansickle AT worldnet DOT att DOT net> writes:
> 
> > # Why should this...:
> > rm //a/bunch/of/files/out/on/a/super/slow/server/*
> > # ...block this:
> > gcc hello.c
> > 
> > Obviously you're never going to be able to take advatage of all 
> > non-dependencies, but as a wise man once told me, "you can't win if 
> > you don't enter".
> 
> make -j?

make -j serialises at directory borders (at a minimum).
You might like to review the 'recursive make considered harmful' paper
(if you haven't already). 

such an approach allows hugely decreased make times in the general case,
by reducing
forks()
dependency recalculations
increased parallelism (partly by reduced serialisation of
non-dependencies).

I routinely do this with automake - I have One, or at most 3
Makefile.am's for projects, even quite large ones, and make -j3 just
flies along, even with lots and lots of little modular directories and
dependencies turned on.

Rob

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