[Haskell-cafe] [Haskell-beginners] Int V.S. Word32
freizl at gmail.com
Sun Nov 20 07:50:09 CET 2011
Hmm... I think I made a little confusion so I put my finding here:
I do got stack overflow thus need several compile opts to fix it.
Not sure if it is what you mean by "You get overflow using 32-bit types
On Sat, Nov 19, 2011 at 10:49 PM, Daniel Fischer <
daniel.is.fischer at googlemail.com> wrote:
> On Saturday 19 November 2011, 09:09:50, Haisheng Wu wrote:
> > Hello,
> > I got great performance difference for the following code if I used
> > type `Int` rather than `Data.Word.Word32`.
> > Anyone can help to explain why such difference?
> Short answer: GHC optimises Int calculations far better than Word32
> calculations, rather, it optimises more calculations for Int than for
> Word32. It also optimises more calculations for Word than for Word32, but
> not as many as for Int.
> The reason is that Int (and Word) are (at least expected to be) far more
> often used, so the effort has gone to these types primarily. Work is being
> done to get the fixed-width types on par, but it's not around the corner
> You can try using Word instead of Word32, that's likely to be faster.
> > Thanks a lot.
> > -Simon
> > module Main where
> > import Data.Word
> > main :: IO ()
> > main = print $ p14
> > p14 = maximum [ (startChain n 0, n) | n <- [2..1000000] ]
> You get overflow using 32-bit types here.
> > startChain :: Word32 -> Int -> Int
> > startChain 1 count = count + 1
> > startChain n count = startChain (intTransform n) (count+1)
> > intTransform :: Word32 -> Word32
> > intTransform n
> > | even n = n `div` 2
> > | otherwise = 3 * n + 1
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