[Haskell-cafe] Significant slow-down in parallel code?

[Jamie Morgenstern]

I am using 6.12... are there any good pointers as to how one uses
threadscope?

On Mon, Jan 4, 2010 at 3:14 PM, Neil Mitchell <ndmitchell at gmail.com> wrote:

> Hi Jamie,
>
> First question, what version of GHC are you using? There are
> significant performance improvements to parallel code in GHC 6.12, so
> it's worth an upgrade. Once you've upgraded you might want to try out
> threadscope which is designed to help track down these sorts of
> problems.
>
> If you are using 6.10, I recommend turning off parallel garbage
> collection with the RTS flags (see the manual) as that can cause
> slowdowns.
>
> Thanks, Neil
>
> 2010/1/4 Jamie Morgenstern <cantthinkthinkpink at gmail.com>:
> > Hello;
> >
> >  I have a piece of code in which I employ the `par` construct to add some
> implicit parallelism
> > to a theorem prover. However, when running the *same* code with
> >
> > +RTS -N1
> > +RTS -N5
> > +RTS -N10
> >
> > I see a huge slowdown (a factor of 50 with 5 processes and a factor of
> 100 for 10 on an 8-core machine).
> >
> > Very little time is being spent using the garbage collector. Any
> suggestions?
> >
> > Thanks,
> > -Jamie
> >
> > _______________________________________________
> > Haskell-Cafe mailing list
> > Haskell-Cafe at haskell.org
> > http://www.haskell.org/mailman/listinfo/haskell-cafe
> >
> >
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.haskell.org/pipermail/haskell-cafe/attachments/20100104/5efb71ab/attachment.html