No "last core parallel slowdown" on OS X

Tyson Whitehead twhitehead at
Tue Apr 21 10:14:37 EDT 2009

On April 21, 2009 04:39:40 Simon Marlow wrote:
> > These ratios match up like physical constants, or at least invariants of
> > my Haskell implementation. However, the user time is constant on OS X, so
> > these ratios reflect the actual parallel speedup on OS X. The user time
> > climbs steadily on Linux, significantly diluting the parallel speedup on
> > Linux. Somehow, whatever is going wrong in the interaction between
> > Haskell and Linux is being captured in this increase in user time.
> We can't necessarily blame this on Linux: the two machines have
> different hardware.  There could be cache-effects at play, for
> example.

Why not try booting a CD or thumb-drive linux distro (e.g., ubuntu live) on 
your 2.4 GHz Q6600 OS X box and see how things stack up.  It would certainly 
eliminate any questions of hardware differences.

Cheers!  -Tyson
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