Partial implementation

app/Main.hs

@@ -1,33 +1,46 @@
 module Main (main) where
 
 import Control.Exception
-import Data.Vector qualified as V
 import Poly
 import System.Random
 import System.TimeIt
+import Control.Monad
 
 main :: IO ()
 main = do
   do
-    let f :: Poly Int = Poly (V.fromList [1, 2, 3])
-    let g :: Poly Int = Poly (V.fromList [4, 5])
+    let f :: Poly Int = makePoly [1, 2, 3]
+    let g :: Poly Int = makePoly [4, 5]
     putStrLn $ "f: " <> show f <> ", g: " <> show g
     putStrLn $ "f + g: " <> show (f + g)
     putStrLn $ "Naive f * g: " <> show (f * g)
     putStrLn $ "Karatsuba f * g: " <> show (normalize $ karatsubaMult f g)
 
+
   putStrLn ""
+  experimentFor 250
   experimentFor 500
   experimentFor 1000
+  karatsubaFor 3000
   where
     experimentFor n = do
       setStdGen $ mkStdGen 10
-      let randomPoly size = Poly <$> V.replicateM size (randomRIO (-100, 100))
+      let randomPoly size = makePoly <$> replicateM size (randomRIO (-100, 100))
       putStrLn $ "Size " <> show n
       f :: Poly Int <- randomPoly n
       g :: Poly Int <- randomPoly n
       putStrLn "naive:"
       _ <- timeIt $ evaluate (f * g)
       putStrLn "Karatsuba:"
-      _ <- timeIt $ evaluate (f * g)
+      _ <- timeIt $ evaluate (karatsubaMult f g)
+      putStrLn "Finished"
+
+    karatsubaFor n = do
+      setStdGen $ mkStdGen 10
+      let randomPoly size = makePoly <$> replicateM size (randomRIO (-100, 100))
+      putStrLn $ "Size " <> show n
+      f :: Poly Int <- randomPoly n
+      g :: Poly Int <- randomPoly n
+      putStrLn "Karatsuba:"
+      _ <- timeIt $ evaluate (karatsubaMult f g)
       putStrLn "Finished"

src/Poly.hs

@@ -2,64 +2,67 @@ module Poly where
 
 import Data.List
 import Data.Maybe
-import Data.Vector qualified as V
+import Data.Vector.Unboxed qualified as V
 
 -- Zip two vectors while padding 0s on the shorter vector.
-vecZipPad0With :: (Num a) => (a -> a -> a) -> V.Vector a -> V.Vector a -> V.Vector a
+vecZipPad0With :: (V.Unbox a, Num a) => (a -> a -> a) -> V.Vector a -> V.Vector a -> V.Vector a
 vecZipPad0With f xs ys = V.generate (max (V.length xs) (V.length ys)) $
   \i -> fromMaybe 0 (xs V.!? i) `f` fromMaybe 0 (ys V.!? i)
 
 -- | Polynomial type.
 --
--- >>> Poly (V.fromList [1 .. 5])
+-- >>> Poly (V.fromList [1 :: Int .. 5])
 -- 1 X^0 + 2 X^1 + 3 X^2 + 4 X^3 + 5 X^4
 
--- >>> Poly (V.fromList [1, 2]) * Poly (V.fromList [3, 4, 5])
+-- >>> Poly (V.fromList [1 :: Int, 2]) * Poly (V.fromList [3 :: Int, 4, 5])
 -- 3 X^0 + 10 X^1 + 13 X^2 + 10 X^3
 
--- >>> Poly (V.fromList [1, 2]) * Poly (V.fromList [])
+-- >>> Poly (V.fromList [1 :: Int, 2]) * Poly (V.fromList [])
 -- 0 X^0
 newtype Poly a = Poly (V.Vector a)
   deriving (Eq)
 
+makePoly :: (V.Unbox a) => [a] -> Poly a
+makePoly = Poly . V.fromList
+
 -- | Degree, assuming top term is nonzero
-degree :: Poly a -> Int
-degree (Poly f) = length f - 1
+degree :: (V.Unbox a) => Poly a -> Int
+degree (Poly f) = V.length f - 1
 
 -- | Shift up polynomial by X^n
-shiftUp :: (Num a) => Int -> Poly a -> Poly a
+shiftUp :: (V.Unbox a, Num a) => Int -> Poly a -> Poly a
 shiftUp n (Poly f) = Poly $ V.replicate n 0 <> f
 
 -- | Shift down polynomial by X^n
-shiftDown :: Int -> Poly a -> Poly a
+shiftDown :: (V.Unbox a) => Int -> Poly a -> Poly a
 shiftDown n (Poly f) = Poly $ V.drop n f
 
 -- | Remainder under X^n
-remXn :: Int -> Poly a -> Poly a
+remXn :: (V.Unbox a) => Int -> Poly a -> Poly a
 remXn n (Poly f) = Poly $ V.take n f
 
 -- | Normalize polynomial, removing leading 0s
--- 
--- >>> normalize $ Poly (V.fromList [1, 0, 0])
+--
+-- >>> normalize $ Poly (V.fromList [1 :: Int, 0, 0])
 -- 1 X^0
--- 
--- >>> normalize $ Poly (V.fromList [1, 2, 3, 0])
+--
+-- >>> normalize $ Poly (V.fromList [1 :: Int, 2, 3, 0])
 -- 1 X^0 + 2 X^1 + 3 X^2
-normalize :: (Eq a, Num a) => Poly a -> Poly a
+normalize :: (Eq a, Num a, V.Unbox a) => Poly a -> Poly a
 normalize (Poly f) = Poly remain
   where
     (_, remain) = V.spanR (== 0) f
 
 -- | This Num instance implements the classical multiplication.
-instance (Num a) => Num (Poly a) where
+instance (Num a, V.Unbox a) => Num (Poly a) where
   (+) :: Poly a -> Poly a -> Poly a
   Poly f + Poly g = Poly $ vecZipPad0With (+) f g
   (-) :: Poly a -> Poly a -> Poly a
   Poly f - Poly g = Poly $ vecZipPad0With (-) f g
   (*) :: Poly a -> Poly a -> Poly a
-  Poly f * Poly g = sum (Poly <$> mults)
+  Poly f * Poly g = sum (map Poly mults)
     where
-      mults = V.imap (\i fi -> V.map (fi *) (V.replicate i 0 <> g)) f
+      mults = zipWith (\i fi -> V.map (fi *) (V.replicate i 0 <> g)) [0 ..] (V.toList f)
   negate :: Poly a -> Poly a
   negate (Poly f) = Poly $ V.map negate f
   abs :: Poly a -> Poly a
@@ -69,11 +72,10 @@ instance (Num a) => Num (Poly a) where
   fromInteger :: Integer -> Poly a
   fromInteger = Poly . V.singleton . fromInteger
 
-instance (Show a) => Show (Poly a) where
-  show :: (Show a) => Poly a -> String
-  show (Poly p) = intercalate " + " . V.toList $ V.imap (\i coeff -> show coeff <> " X^" <> show i) p
+instance (V.Unbox a, Show a) => Show (Poly a) where
+  show (Poly p) = intercalate " + " $ zipWith (\i coeff -> show coeff <> " X^" <> show i) [0 :: Int ..] (V.toList p)
 
-karatsubaMult :: (Num a) => Poly a -> Poly a -> Poly a
+karatsubaMult :: (Num a, V.Unbox a) => Poly a -> Poly a -> Poly a
 karatsubaMult a b = atLog degBound a b
   where
     degBound = fromJust $ find (> max (degree a) (degree b)) [2 ^ i | i <- [0 :: Int ..]]