I'm implementing Conway's Life in Haskell; my basic implementation is
attached. Does anyone have suggestions for optimizations (or alternative
representations)? It's interesting to note that the difference between
this with no ghc optimization, -O, and -O2 is pretty striking; on my
computer, it's about seven seconds, two seconds, and one second runtime,
respectively.
Abe
module Main where
import Data.Array.IArray
import Data.Array.Unboxed
import Data.Ix
import System.Random
type Grid = UArray (Int, Int) Int
randomGrid :: (RandomGen g) => g -> Int -> Grid
randomGrid g s = listArray b $ map (\x -> if x then 1 else 0) $ take (rangeSize b) $
randoms g
where b = ((0,0),(s-1,s-1))
getCell :: Grid -> (Int, Int) -> Int
getCell g c@(x,y) = if (x < xmin) || (x > xmax) || (y < ymin) || (y >= ymax) then 0
else g ! c
where ((xmin, ymin), (xmax, ymax)) = bounds g
update :: Grid -> Grid
update g = array (bounds g) $ map aux $ assocs g
where aux (c@(x,y),e) = let around = map (getCell g) $ filter (/= (x,y)) $ range
((x-1,y-1),(x+1,y+1))
in (c,rule (sum around) e)
rule 2 e = e
rule 3 e = 1
rule _ _ = 0
printGrid :: Grid -> IO ()
printGrid g = do let ((xmin, ymin), (xmax, ymax)) = bounds g
mapM_ aux $ map (\x -> range ((x,ymin),(x,ymax))) [xmin..xmax]
putStrLn ""
where aux ixs = do mapM_ (putStr . show) $ map (g!) ixs
putStrLn ""
main :: IO ()
main = printGrid $ (iterate update (randomGrid (mkStdGen 0) 50)) !! 100
