On 20 September 2012 22:55, Gregory Collins <greg@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.