module Main where
import qualified Data.ByteString.Lazy as B
import Data.ByteString.Nums.Careless -- from bytestring-nums package
bint :: B.ByteString -> Int
bint = int
main = do
line : rest <- B.split 10 `fmap` B.getContents
let [n, k] = map int . B.split 32 $ line
putStrLn . show . length . tail . filter ((==0).(`mod`k).bint) $ rest
This does a 100MB file in 2.7s (probably because the file is cached by
the filesystem).
2009/8/30 Steve
Hi, I'm tackling a Sphere Online Judge tutorial question where it tests how fast you can process input data. You need to achieve at least 2.5MB of input data per second at runtime (on an old machine running ghc 6.6.1). This is probably close to the limit of Haskell's ability.
https://www.spoj.pl/problems/INTEST/
I can see that 24 haskell programmers have solved it, but most are very close to the 8 secs limit (and 6/24 are even over the limit!).
Here's my code. It fails with a "time limit exceeded" error. (I think it would calculate the correct result, eventually).
module Main where
import qualified Data.List as DLi import qualified System.IO as SIO
main :: IO () main = do line1 <- SIO.hGetLine SIO.stdin let k = read $ words line1 !! 1 s <- SIO.hGetContents SIO.stdin print $ count s k
count :: String -> Int -> Int count s k = DLi.foldl' foldFunc 0 (map read $ words s) where foldFunc :: Int -> Int -> Int foldFunc a b | mod b k == 0 = a+1 | otherwise = a
I tried using Data.ByteString but then found that 'read' needs a String, not a ByteString. I tried using buffered IO, but it did not make any difference.
Any suggestions on how to speed it up?
Regards, Steve
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