[Haskell-cafe] [ANNOUNCE] hashable-generics

[Clark Gaebel]

Thanks a lot!

I've updated the benchmark accordingly, and have released a new version
without the 1.3x slowdown disclaimer as generic-hashable 1.1.8.

  - Clark


On Sun, Nov 4, 2012 at 10:25 AM, Herbert Valerio Riedel <hvr at gnu.org> wrote:

> Clark Gaebel <cgaebel at uwaterloo.ca> writes:
>
> [...]
>
> > Oh yeah, and if anyone wants to help me figure out why it's 1.3x slower
> > than my hand-rolled instances, that would be really helpful.
>
> [...]
>
> I've taken a look at the bench/Bench.hs benchmark[1]:
>
> The generated Core looks almost[2] the same as your 'HandRolled'; but
> the 1.3x slow-down factor seems to be caused by the way the
> 'bigGenericRolledDS' CAF is defined in the test-harness: if I define it
> explicitly (i.e. just as 'bigHandRolledDS' is defined, and not as an
> isomorphic transformation of the 'bigHandRolledDS' value) the benchmark
> results in both versions having more or less equal performance as would
> be expected.
>
>
>  [1]:
> https://github.com/wowus/hashable-generics/blob/master/bench/Bench.hs
>
>  [2]: with the following change, it would look exactly the same (modulo
>       alpha renamings):
>
> --8<---------------cut here---------------start------------->8---
> --- a/bench/Bench.hs
> +++ b/bench/Bench.hs
> @@ -18,7 +18,7 @@ data GenericRolled = GR0
>      deriving Generic
>
>  instance Hashable HandRolled where
> -    hashWithSalt salt HR0       = hashWithSalt salt $ (Left () :: Either
> () ())
> +    hashWithSalt salt HR0       = hashWithSalt salt $ ()
>      hashWithSalt salt (HR1 mi)  = hashWithSalt salt $ (Right $ Left mi ::
> Either () (Either (Maybe Int) ()))
>      hashWithSalt salt (HR2 x y) = hashWithSalt salt $ (Right $ Right (x,
> y) :: Either () (Either () (HandRolled, HandRolled)))
> --8<---------------cut here---------------end--------------->8---
>
> hth,
> hvr
>
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