[web-devel] Data.Word8 (word8 library)

[Gregory Collins]

On Thu, Sep 20, 2012 at 11:57 PM, Bas van Dijk <v.dijk.bas at gmail.com> wrote:

> On 20 September 2012 22:55, Gregory Collins <greg at gregorycollins.net>
> wrote:
> > consequently, there seems to be no reason to use the word8 library: not
> only
> > is it not faster, it's actually a pessimization.
>
> When I run the following benchmark:
>
> main :: IO ()
> main = do
>     input <- S.readFile "bench.hs"
>     defaultMain
>         [ bench "Word8-local"    $ nf (S.length . S.map toLower8) input
>         , bench "Char8 toLowerC" $ nf (S.length . S8.map toLowerC) input
>         ]
>
> toLower8 :: Word8 -> Word8
> toLower8 w
>   | isUpper8 w = w + 32
>   | otherwise = w
> {-# INLINE toLower8 #-}
>
> isUpper8 :: Word8 -> Bool
> isUpper8 w = 0x41 <= w && w <= 0x5a
>           || 0xc0 <= w && w <= 0xd6
>           || 0xd8 <= w && w <= 0xde
> {-# INLINE isUpper8 #-}
>
> toLowerC :: Char -> Char
> toLowerC w
>     | isUpperC w = unsafeChr $ ord w + 0x20
>     | otherwise = w
>
> isUpperC :: Char -> Bool
> isUpperC w = '\x41' <= w && w <= '\x5a'
>           || '\xc0' <= w && w <= '\xd6'
>           || '\xd8' <= w && w <= '\xde'
>
> I get the following results:
>
> benchmarking Word8-local
> mean: 8.939985 us, lb 8.921876 us, ub 8.960350 us, ci 0.950
> std dev: 97.99953 ns, lb 86.79926 ns, ub 113.6396 ns, ci 0.950
>
> benchmarking Char8 toLowerC
> mean: 3.468023 us, lb 3.461577 us, ub 3.475718 us, ci 0.950
> std dev: 35.93801 ns, lb 30.56892 ns, ub 49.77021 ns, ci 0.950
>
> However when I _remove_ the INLINE pragmas they become equally fast:
>

That's what I originally expected the results to be. The fact that removing
those INLINE pragmas makes things better is........strange. I'm going to
forward this thread to Simon to see what he thinks about it.

G
-- 
Gregory Collins <greg at gregorycollins.net>
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