Bulat Ziganshin wrote:
Wednesday, January 18, 2006, 3:33:40 PM, you wrote:
SMH> and gets a runtime for the GHC-compiled binary that's about 10x as long
SMH> as for GCC. Simon M. tells me this should be much better. Here are the
attached version is only 5 times slower :) please note that
1) unsafeRead/Write indexes from 0 and don't checks bounds (just C-like :)
2) generating random values takes about 1.5-2 seconds by itself.
Haskell's RNG is very different from C's one
I squeezed a bit more out (see attached). I think the main bottleneck
is now the random number generator, in particular it is supplying boxed
Doubles which have to be unboxed again before storing in the array.
Cheers,
Simon
import Data.Array.IO
import Data.Array.Base
import System.Environment (getArgs)
import System.Random
type Vector = IOUArray Int Double
main = do (n:f:m:_) <- getArgs
let (nelems,niterations) = case f of
"elements" -> (read n, read m)
"iterations" -> (read m, read n)
x <- newArray (0,nelems-1) 0 :: IO Vector
v <- newArray_ (0,nelems-1) :: IO Vector
x `seq` v `seq` return ()
for 0 nelems $ \i ->
do r <- randomRIO (-1,1)
unsafeWrite v i r
for 0 niterations $ \_ ->
for 0 nelems $ \i ->
do xi <- unsafeRead x i
vi <- unsafeRead v i
unsafeWrite x i (xi+vi)
--for 0 nelems $ \i ->
-- do xi <- unsafeRead x i
-- putStr (show xi)
-- putChar ' '
--putChar '\n'
for :: Int -> Int -> (Int -> IO a) -> IO ()
-- Faster equivalent of "mapM_ action [from..to-1]"
for from to action | from `seq` to `seq` False = undefined
for from to action = go from
where
go i | i>=to = return ()
| otherwise = do action i
go $! (i+1)
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