2008/2/17, Jonathan Cast <[EMAIL PROTECTED]>:
>
> 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.
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