[Haskell-cafe] Threading and Mullticore Computation

[mwinter at brocku.ca]

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 <dons at galois.com> wrote:
> > allbery:
> >> On 2009 Mar 3, at 12:31, mwinter at brocku.ca wrote:
> >>> 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.
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