[QuickCheck] [PATCH] Fix a performance issue

[Nick Smallbone]

Thanks Simon! I've adapted your patch slightly and pushed it.

Nick

On 18 November 2012 15:09, Simon Hengel <sol at typeful.net> wrote:
> Hi,
> here are the numbers.
>
> Without producing any output:
>
>     -- file main.hs
>     main = replicateM_ 100 . (quickCheckWith stdArgs {chatty = False}) $
>       \x y -> x /= y ==> x /= (y :: Int)
>
>     $ ghc main.hs && time ./main
>     real    0m0.851s
>     user    0m0.844s
>     sys     0m0.008s
>
>
> QuickCheck's current default behavior:
>
>     -- file main.hs
>     main = replicateM_ 100 . quickCheck $
>       \x y -> x /= y ==> x /= (y :: Int)
>
>     $ ghc main.hs && time ./main
>     real    0m6.650s
>     user    0m1.940s
>     sys     0m2.404s
>
>
> QuickCheck's default behavior with my patch:
>
>     real    0m1.697s
>     user    0m1.088s
>     sys     0m0.132s
>
> I hope it is obvious how to interpret this.
>
> The solution was pointed out by parcs in a comment to GHC #7418 [1].
>
> Cheers,
> Simon
>
> [1] http://hackage.haskell.org/trac/ghc/ticket/7418#comment:1
>
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