Use hmatrix to generate random input with Gaussian distribution.

LowPass.hs

@@ -8,8 +8,10 @@ import Data.List                    as L
 import Data.Vector.Storable         as V
 import Data.Vector.Storable.Mutable as MV
 import Numeric.LinearAlgebra        as LA
+import Numeric.GSL.Fourier          as LA
 
 import Control.Applicative
+import Data.Complex
 import System.Random
 import System.Time
 import Text.Printf
@@ -49,13 +51,15 @@ convolve kernel input = V.generate osize $ \j -> rkernel <.> V.slice j ksize inp
 main :: IO ()
 main = do
    let isize = 2000000
-   (input,  inputTime)  <- time $ V.fromListN isize . randoms <$> newStdGen
+   seed <- randomIO
+   (input,  inputTime)  <- time $ return $ LA.randomVector seed Gaussian isize
    (_,      kernelTime) <- time $ return lowPassKernel
    (result, resultTime) <- time $ return $ convolve lowPassKernel input
-   V.mapM_ (printf "%0.6f\n") $ V.slice 0 50 result
-   printf "Input  Time: %0.6f seconds\n" $ inputTime
-   printf "Kernel Time: %0.6f seconds\n" $ kernelTime
-   printf "Result Time: %0.6f seconds\n" $ resultTime
+   V.mapM_ (printf "%10.6f\n") $ V.slice 0 50 result
+   --V.mapM_ (printf "%10.6f\n") $ V.map magnitude $ LA.fft $ V.map (:+0) result
+   printf "Input  Time: %8.6f seconds\n" $ inputTime
+   printf "Kernel Time: %8.6f seconds\n" $ kernelTime
+   printf "Result Time: %8.6f seconds\n" $ resultTime
 
 time :: IO a -> IO (a, Double)
 time f = do