Re: [Haskell-cafe] Basic questions about concurrency in Haskell

On Wed, Aug 5, 2009 at 6:59 PM, Thomas Witzel wrote:

2. I started with the very simple nfib example given in the manual for Control.Parallel (Section 7.18). On my systems using multiple cores makes the code actually slower than just using a single core. While the manual cautions that this could be the case for certain algorithms, I'm wondering whether this is the desired behaviour for this example.

I'm using ghc 6.10.4 right now.

IIRC the development version of GHC has some major work to optimize concurrency, so it may be worth trying that. In particular I believe it executes sparks in batches, to reduce the overhead (which hopefully fixes your issue). -- Sebastian Sylvan