Re: [Haskell-cafe] Threading and Mullticore Computation

I am using GHC 6.8.3. The -O2 option made both runs faster but the 2 core run is still much slower that the 1 core version. Will switching to 6.10 make the difference? On 3 Mar 2009 at 18:46, Svein Ove Aas wrote:

On Tue, Mar 3, 2009 at 6:41 PM, Don Stewart wrote:

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allbery:

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On 2009 Mar 3, at 12:31, mwinter@brocku.ca wrote:

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In both runs the same computations are done (sequentially resp. parallel), so the gc should be the same. But still using 2 cores is much slower than using 1 core (same program - no communication).

The same GCs are done, but GC has to be done on a single core (currently; parallel GC is in development) so you will see a lot more lock contention when the GC kicks in.

Assuming he is using GHC 6.10, the parallel GC is enabled by default when you use -Nn where n > 1. That's is -N4 will use -g4   (4 cores to collect). So GC should be the same or a little faster.

Further, GHC (6.10 at least) uses one allocation area per thread, meaning there's no contention on allocation.

I'd echo the request to try it with -O2, though. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe