not fully correct crc16 implementation

vector.hs

-- Vector:

icsum16 :: Word32 -> V.Vector Word16 -> Word32
icsum16 !i bv = V.foldl' (\a -> (+a).fromIntegral) i bv
{-# INLINE icsum16 #-}

icsum16 :: Word32 -> Vector Word16 -> Word32
icsum16 =
  \ (eta :: Word32) (eta1 :: Vector Word16) ->
    let { Vector ipv ipv1 ipv2 ~ _ <- eta1 } in
    let { W32# ww ~ _ <- eta } in
    letrec {
      $s$wfoldlM'_loop :: Word# -> Int# -> Word#
      $s$wfoldlM'_loop =
        \ (sc :: Word#) (sc1 :: Int#) ->
          case >=# sc1 ipv of _ {
            False ->
              let { (# ipv3, ipv5 #) ~ _
              <- readWord16OffAddr# ipv1 sc1 realWorld#
              } in
              let { __DEFAULT ~ _ <- touch# ipv2 ipv3 } in
              $s$wfoldlM'_loop (narrow32Word# (plusWord# ipv5 sc)) (+# sc1 1);
            True -> sc
          }; } in
    let { __DEFAULT ~ ww1 <- $s$wfoldlM'_loop ww 0 } in W32# ww1

benchmarking csumNew
mean: 381.5357 ns, lb 379.4919 ns, ub 384.6853 ns, ci 0.950
std dev: 12.81831 ns, lb 9.142332 ns, ub 16.99766 ns, ci 0.950
found 12 outliers among 100 samples (12.0%)
  11 (11.0%) high severe
variance introduced by outliers: 29.670%
variance is moderately inflated by outliers




-- First approach to primops
--icsum16p :: Word32 -> V.Vector Word16 -> Word32
icsum16p !i bv = runST $ do
    let crc a x = do
        let !(W16# w#) = x
        return $ a + W32# w#
    V.foldM' crc i bv

$wicsum16p
  :: Word# -> Int# -> Addr# -> ForeignPtrContents -> Word32
$wicsum16p =
  \ (ww :: Word#)
    (ww1 :: Int#)
    (ww2 :: Addr#)
    (ww3 :: ForeignPtrContents) ->
    runSTRep
      (\ (@ s) (w :: State# s) ->
         letrec {
           $s$wa1 :: Word# -> Int# -> State# s -> (# State# s, Word32 #)
           $s$wa1 =
             \ (sc :: Word#) (sc1 :: Int#) (sc2 :: State# s) ->
               case >=# sc1 ww1 of _ {
                 False ->
                   let { (# ipv, ipv1 #) ~ _
                   <- readWord16OffAddr# ww2 sc1 realWorld#
                   } in
                   let { __DEFAULT ~ _ <- touch# ww3 ipv } in
                   $s$wa1 (narrow32Word# (plusWord# sc ipv1)) (+# sc1 1) sc2;
                 True -> (# sc2, W32# sc #)
               }; } in
         $s$wa1 ww 0 w)

icsum16p :: Word32 -> Vector Word16 -> Word32
icsum16p =
  \ (w :: Word32) (w1 :: Vector Word16) ->
    let { W32# ww ~ _ <- w } in
    let { Vector ww1 ww2 ww3 ~ _ <- w1 } in $wicsum16p ww ww1 ww2 ww3


benchmarking csumNew1
mean: 387.5422 ns, lb 385.8914 ns, ub 390.4234 ns, ci 0.950
std dev: 10.89284 ns, lb 7.120208 ns, ub 16.06513 ns, ci 0.950
found 13 outliers among 100 samples (13.0%)
  2 (2.0%) high mild
  11 (11.0%) high severe
variance introduced by outliers: 22.861%
variance is moderately inflated by outliers



-- PrimOps by hands
icsum16p2 :: Word32 -> Addr# -> Int -> Word32
icsum16p2 !(W32# i#) a# !l = runST (go i# 0)
    where
      a = P.Addr a#
      {-# INLINE a #-}
      -- go :: Word# -> Int -> m Word32
      go w# x | x >= l = return (W32# w#)
              | otherwise = do
         v <- a `P.readOffAddr` x
         let !(W16# v#) = v
         go (narrow32Word# (w# `plusWord#` v#)) (x+1)
      {-# INLINE go #-}
{-# INLINE icsum16p2 #-}

icsum16p2 :: Word32 -> Addr# -> Int -> Word32
icsum16p2 =
  \ (eta :: Word32) (eta1 :: Addr#) (eta2 :: Int) ->
    let { W32# i# ~ _ <- eta } in
    let { I# ipv ~ _ <- eta2 } in
    runSTRep
      (\ (@ s) (w :: State# s) ->
         letrec {
           $wa4 :: Word# -> Int# -> State# s -> (# State# s, Word32 #)
           $wa4 =
             \ (w1 :: Word#) (ww :: Int#) (w2 :: State# s) ->
               case >=# ww ipv of _ {
                 False ->
                   let { (# ipv1, ipv2 #) ~ _
                   <- readWord16OffAddr# eta1 ww (w2 `cast` ...)
                   } in
                   $wa4
                     (narrow32Word# (plusWord# w1 ipv2)) (+# ww 1) (ipv1 `cast` ...);
                 True -> (# w2, W32# w1 #)
               }; } in
         $wa4 i# 0 w)

benchmarking csumNew2
mean: 719.7642 ns, lb 716.4036 ns, ub 725.5346 ns, ci 0.950
std dev: 21.82769 ns, lb 14.58964 ns, ub 31.41340 ns, ci 0.950
found 8 outliers among 100 samples (8.0%)
  8 (8.0%) high severe
variance introduced by outliers: 25.761%
variance is moderately inflated by outliers