[Haskell-cafe] GHC strange behavior

Don Stewart dons at galois.com
Sat Feb 16 19:09:12 EST 2008

> 2008/2/17, Jonathan Cast <jonathanccast at fastmail.fm>:
> >
> > Wild guess?  If you leave o as a thunk, to be evaluated once the
> > program has e, then it has numbers, so you keep the entire 10-million
> > entry list in memory.  Evaluating e and o in parallel allows the
> > system to start garbage collecting cons cells from numbers much
> > earlier, which reduces residency (I'd've been unsuprised at more than
> > two orders of magnitude).  Managing the smaller heap (and especially
> > not having to copy numbers on each GC) then makes the garbage
> > collector go much faster, so you get a smaller run time.
> >
> But I also tested it on P-IV 3.0 with HT and 1GB (single core) running
> Windows-XP (ghc 6.8.2), and it works fine (fast & low GC) in all three
> cases without significant difference. Sure it didn't runs faster with
> -N2 'cause it's not dual-core.

What flags did you compile the code with? 

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