Hello Dan, Thursday, November 8, 2007, 9:33:12 PM, you wrote:
main = do a <- newArray (0,n-1) 1.0 :: IO (IOUArray Int Double) forM_ [0..n-2] $ \i -> do { x <- readArray a i; y <- readArray a (i+1); writeArray a (i+1) (x+y) } x <- readArray a (n-1) print x
1. ghc doesn't implement loop unrolling, even in -O2 mode 2. forM_ may have its own overheads, i'm not sure 3. add strictness annotations: forM_ [0..n-2] $ \i -> do { return $! i; x <- readArray a i; return $! x; y <- readArray a (i+1); return $! y; writeArray a (i+1) (x+y) } such cycle should be approx. 3-10 times slower than C one -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com