vec.hs

{-# LANGUAGE ForeignFunctionInterface #-}
import System.Environment
import qualified Data.Vector as V
import Control.Monad (join)
import Data.Word
import Criterion.Main
import Foreign.C
import Foreign.Marshal
import Foreign.Ptr


foreign import ccall "result_c" _result_c :: Int -> Ptr Int -> Ptr Int -> IO Int
result_c n = alloca (\x -> _result_c n x x)

foreign import ccall "result_llvm" _result_llvm :: Int -> Ptr Int -> Ptr Int -> IO Int
result_llvm n = alloca (\x -> _result_llvm n x x)

type W = Word32

next a = Just . join (,) $ (if even a then a else 3*a+1) `div` 2

len = (+1) . V.length . V.takeWhile (/=1) . V.unfoldr next

result :: W -> (Int,W)
result = V.maximum . V.map (\x -> (len x, x)) . V.enumFromTo 1

main' = do
  [a0] <- getArgs
  let max_a0 = read a0 :: W
  print . result $ max_a0


main = defaultMain . map group $ [100000,250000,500000,1000000]
    where group n = bgroup (show n) [
                     bench "data.vector" $ nf result n,
                     bench "gcc -O2" $ nfIO (result_c (fromIntegral n)),
                     bench "llvm -O2" $ nfIO (result_llvm (fromIntegral n))
                    ]

-- main = do r <- result_c 100000
--           print (r, result 100000)