I've been using it on a 4 processor Sparc system and even a 12 processor
MVS mainframe, and it REALLY speeds things up.  Not sure that it really
helps too much on single processor systems.  You have to be careful in
the make files.  Make is smart enough to know that it can compile 2
elements that share the same target, and that that target is not to be
done, until all it's dependents are complete.  You can't start a link
until the compiles are complete.

The problem is that many makefiles use rules that do not clearly define
these dependencies.  Things like 'for' iterations and sub-makes are
easily broken when using the shotgun (-j) option.

Mike Jentges wrote:
> 
> > I've been playing with make's -j capability. -Most- of the time this works
> > great, but every now and then certain things just don't compile when I do
> a
> > -j 2, -but- compile files with a -j 1 or no -j option.
> >
> > Anyone know why this is?
> >
> > What do make constructs cause this to fail?
> 
> I always attributed it to the fact that certain things had to be made in
> certain order in certain circumstances. Other jobs it doesn't matter.
> Almost like it would get ahead of itself and what it needed to do a task was
> not done yet.
> ??
> 
> -mj
> 
> >
> >
> > --
> > Bob Tanner <tanner at real-time.com>         | Phone : (952)943-8700
> > http://www.mn-linux.org, Minnesota, Linux | Fax   : (952)943-8500
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> >
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> Minnesota
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> >
> 
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