{-# LANGUAGE MultiParamTypeClasses #-}
module Basement.Alg.Mutable
( inplaceSortBy
) where
import GHC.Types
import GHC.Prim
import Basement.Compat.Base
import Basement.Numerical.Additive
import Basement.Numerical.Multiplicative
import Basement.Types.OffsetSize
import Basement.PrimType
import Basement.Monad
import Basement.Alg.Class
inplaceSortBy :: (PrimMonad prim, RandomAccess container prim ty)
=> (ty -> ty -> Ordering)
-> (Offset ty)
-> (CountOf ty)
-> container
-> prim ()
inplaceSortBy :: forall (prim :: * -> *) container ty.
(PrimMonad prim, RandomAccess container prim ty) =>
(ty -> ty -> Ordering)
-> Offset ty -> CountOf ty -> container -> prim ()
inplaceSortBy ty -> ty -> Ordering
ford Offset ty
start CountOf ty
len container
mvec
= Offset ty -> Offset ty -> prim ()
qsort Offset ty
start (Offset ty
start Offset ty -> CountOf ty -> Offset ty
forall ty. Offset ty -> CountOf ty -> Offset ty
`offsetPlusE` CountOf ty
len Offset ty -> Offset ty -> Offset ty
forall a. Offset a -> Offset a -> Offset a
`offsetSub` Offset ty
1)
where
qsort :: Offset ty -> Offset ty -> prim ()
qsort Offset ty
lo Offset ty
hi
| Offset ty
lo Offset ty -> Offset ty -> Bool
forall a. Ord a => a -> a -> Bool
>= Offset ty
hi = () -> prim ()
forall a. a -> prim a
forall (f :: * -> *) a. Applicative f => a -> f a
pure ()
| Bool
otherwise = do
p <- Offset ty -> Offset ty -> prim (Offset ty)
partition Offset ty
lo Offset ty
hi
qsort lo (pred p)
qsort (p+1) hi
pivotStrategy :: Offset ty -> Offset ty -> prim ty
pivotStrategy (Offset Int
low) hi :: Offset ty
hi@(Offset Int
high) = do
let mid :: Offset ty
mid = Int -> Offset ty
forall ty. Int -> Offset ty
Offset (Int -> Offset ty) -> Int -> Offset ty
forall a b. (a -> b) -> a -> b
$ (Int
low Int -> Int -> Int
forall a. Additive a => a -> a -> a
+ Int
high) Int -> Int -> Int
forall a. IDivisible a => a -> a -> a
`div` Int
2
pivot <- container -> Offset ty -> prim ty
forall container (prim :: * -> *) ty.
RandomAccess container prim ty =>
container -> Offset ty -> prim ty
read container
mvec Offset ty
mid
read mvec hi >>= write mvec mid
write mvec hi pivot
pure pivot
partition :: Offset ty -> Offset ty -> prim (Offset ty)
partition Offset ty
lo Offset ty
hi = do
pivot <- Offset ty -> Offset ty -> prim ty
pivotStrategy Offset ty
lo Offset ty
hi
let go Offset ty
i Offset ty
j = do
let fw :: Offset ty -> prim (Offset ty, ty)
fw Offset ty
k = do ak <- container -> Offset ty -> prim ty
forall container (prim :: * -> *) ty.
RandomAccess container prim ty =>
container -> Offset ty -> prim ty
read container
mvec Offset ty
k
if ford ak pivot == LT
then fw (k+1)
else pure (k, ak)
(i, ai) <- Offset ty -> prim (Offset ty, ty)
fw Offset ty
i
let bw Offset ty
k | Offset ty
kOffset ty -> Offset ty -> Bool
forall a. Eq a => a -> a -> Bool
==Offset ty
i = (Offset ty, ty) -> prim (Offset ty, ty)
forall a. a -> prim a
forall (f :: * -> *) a. Applicative f => a -> f a
pure (Offset ty
i, ty
ai)
| Bool
otherwise = do ak <- container -> Offset ty -> prim ty
forall container (prim :: * -> *) ty.
RandomAccess container prim ty =>
container -> Offset ty -> prim ty
read container
mvec Offset ty
k
if ford ak pivot /= LT
then bw (pred k)
else pure (k, ak)
(j, aj) <- bw j
if i < j
then do
write mvec i aj
write mvec j ai
go (i+1) (pred j)
else do
write mvec hi ai
write mvec i pivot
pure i
go lo hi
{-# INLINE inplaceSortBy #-}