Thank you! I am utterly buried just now (POPL) but will get to this. Simon From: glasgow-haskell-users-bounces@haskell.org [mailto:glasgow-haskell-users-bounces@haskell.org] On Behalf Of Bryan O'Sullivan Sent: 12 July 2010 13:58 To: Simon Peyton-Jones Cc: glasgow-haskell-users@haskell.org Subject: Re: Massive slowdown in mwc-random after switching to use of primitive package On Mon, Jul 12, 2010 at 10:40 AM, Bryan O'Sullivan <bos@serpentine.com<mailto:bos@serpentine.com>> wrote: I can probably cook up a smaller repro than Dan, since I depend on neither package for a standalone test case. Let me get cracking on it promptly, and I'll file a ticket later. I filed http://hackage.haskell.org/trac/ghc/ticket/4184 just now, which includes two workarounds that I found for my particular version of the problem, the second of which I stumbled upon quite by accident while creating the standalone repro.