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Re: parallelism: job slots vs. levels

From: Paul D. Smith
Subject: Re: parallelism: job slots vs. levels
Date: Wed, 1 Sep 2004 02:05:53 -0400

%% Dan Jacobson <address@hidden> writes:

  dj> Anyways,
  dj> $ make x& make y& wait
  dj> cannot always be rewritten with -j.

Mm.  I don't think I believe that.  For example, of your makefile had at
the top:

    .PHONY: all rx ry
    all: rx ry

    rx: ; $(MAKE) x
    ry: ; $(MAKE) y

then I think "make -j all" gives you the same behavior.

  dj> $ make -j[whatever number] x y
  dj> will act differently except for special cases of x and y;
  dj> probably when both x and y have no dependencies.

I doubt that as well.  I've already described this in my last message:
these two constructs are identical in function _UNLESS_ their prerequite
subgraphs overlap somewhere.  If they overlap, then the result is not
deterministic in general: it may work fine, or it may fail miserably.

 Paul D. Smith <address@hidden>          Find some GNU make tips at:
 http://www.gnu.org                      http://make.paulandlesley.org
 "Please remain calm...I may be mad, but I am a professional." --Mad Scientist

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