[Haskell-cafe] Basic questions about concurrency in Haskell

Sebastian Sylvan sebastian.sylvan at gmail.com
Wed Aug 5 15:01:09 EDT 2009

On Wed, Aug 5, 2009 at 6:59 PM, Thomas Witzel <witzel.thomas at gmail.com>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
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