Control.Parallel.Strategies.parMap CPU usage

Christian Höner zu Siederdissen choener at
Mon Mar 30 19:36:48 EDT 2009


thank you very much Simon & Don, for the answers.

The latest head gives great results on parallel programs. All cores are
now always at work as I hoped for. So, too, thanks to everybody involved
in the multicore improvements -- they should come very handy. :-)

Thanks again,

* Don Stewart <dons at> [30.03.2009 19:02]:
> choener:
> > Hi,
> >
> > having tried the 6.10.2rc1 release candidate, I still find that "parMap 
> > rnf xs" on a list of thunks xs does not optimally use all available 
> > processors. With N the number of cores, I still see that each block of N 
> > thunks (say: x_1 and x_2) has to be calculated before (x3 and x4) will be 
> > started.
> >
> > Would there be hope that compiling the latest head instead of 2009/03/14 (rc1) gives better results?
> >
> Yes, definitely. The HEAD implements all the `par` improvements
> described in the recent "multicore runtime" paper, as well as giving 
> detailed runtime statistics on spark use.
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