Again: Uniques in GHC

p.k.f.holzenspies at p.k.f.holzenspies at
Tue Oct 7 16:26:24 UTC 2014

Wait, wait, wait! I wasn't talking about a parallel *runtime*. Nothing changes there. All I'm talking about is something that is a very old issue that never got added / solved / resolved. Somewhere on the commentary, or the mailing list, I seem to recall that the generation of Uniques was the bottleneck for the parallelisation of GHC *Itself*. It's about having a compiler using multiple threads and says nothing about programs coming out of it.

I'm all with you on embedded processors and that kind of stuff, but I don't see a pressing need to compile *on* them. Isn't all ARM-stuff assuming cross-compilation?


From: at < at> on behalf of Austin Seipp <austin at>
Sent: 07 October 2014 17:46
To: Holzenspies, P.K.F. (EWI)
Cc: ghc-devs at
Subject: Re: Again: Uniques in GHC

On Tue, Oct 7, 2014 at 1:32 AM,  <p.k.f.holzenspies at> wrote:
> Yes, this approach to a parallel GHC would only work on 64-bit machines. The
> idea is, I guess, that we're not going to see a massive demand for parallel
> GHC running on multi-core 32-bit systems. In other words; 32-bit systems
> wouldn't get a parallel GHC.

Let me make sure I'm understanding this correctly: in this particular
proposed solution, the side effect would be that we no longer have a
capable 32bit runtime which supports multicore parallelism?

Sorry, but I'm afraid this approach is pretty much unacceptable IMO,
for precisely the reason outlined in your last sentence. 32bit systems
are surprisingly commen. I have several multicore 32bit ARMv7 machines
on my desk right now, for example. And there are a lot more of those
floating around than you might think.

If that's the 'cure', I think I (and other users) would consider it
far worse than the disease.

> Regards,
> Philip
> _______________________________________________
> ghc-devs mailing list
> ghc-devs at


Austin Seipp, Haskell Consultant
Well-Typed LLP,

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