Parallel --make (GHC build times on newer MacBook Pros?)

From: Evan Laforge

Sent: Friday, August 26, 2011 6:35 PM Subject: Re: GHC build times on newer MacBook Pros?

On Tue, Aug 23, 2011 at 10:24 AM, David Terei wrote:

...

  I have a 16 core machine at work (with 48GB of ram, a perk of the job   :)). GHC can saturate them all. Can validate GHC in well under 10   minutes on it.

To wander a bit from the topic, when I first saw this I thought "wow, ghc builds in parallel now, I want that" but then I realized it's because ghc itself uses make, not --make.  --make's automatic dependencies are convenient, but figuring out dependencies on every build and not being parallel means make should be a lot faster.  Also, --make doesn't understand the hsc->hs link, so in practice I have to do a fair amount of manual dependencies anyway.  So it inspired me to try to switch from --make to make for my own project.

I'm confused by this as well. Parallelizing --make was one of the first case studies in the smp runtime paper, section 7 in Haskell on a Shared-Memory Multiprocessor There's also a trac ticket http://hackage.haskell.org/trac/ghc/ticket/910with a vague comment that the patch from the paper "almost certainly isn't ready for prime time", but I haven't seen any description of specific problems. Brandon