mlkem-0.2.0.0: src/Matrix.hs

-- |
-- Module      : Matrix
-- License     : BSD-3-Clause
-- Copyright   : (c) 2025 Olivier Chéron
--
-- A matrix here is simply a vector of vectors.  The module also implements
-- 'mulz' as dot product and two utility functions 'mulw' and 'muly' that
-- multiply a matrix and a vector.
--
{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE CPP #-}
module Matrix
    ( create, mulw, muly, mulz
#ifdef ML_KEM_TESTING
    , transpose
#endif
    ) where

import Base
import Math
import Vector (Vector)
import qualified Vector

create :: (KnownNat m, KnownNat n) => (Offset ty -> Offset (Vector n ty) -> ty) -> Vector m (Vector n ty)
create f = Vector.create $ \j -> Vector.create (`f` j)
{-# INLINE create #-}

index :: Vector m (Vector n ty) -> Offset ty -> Offset (Vector n ty) -> ty
index a i j = Vector.index (Vector.index a j) i

mulw :: (KnownNat n, BiMulAdd b a) => Vector m (Vector n b) -> Vector m a -> Vector n a -> Vector n a
mulw a !u !b = Vector.create $ \(Offset i) ->
    Vector.foldIndexWith (\c (Offset j) vu -> biMulAdd (index a (Offset i) (Offset j)) vu c) (Vector.index b (Offset i)) u

muly :: BiMulAdd b a => Vector m (Vector n b) -> Vector n a -> Vector m a
muly a !u = fmap (`mulz` u) a

mulz :: BiMulAdd b a => Vector n b -> Vector n a -> a
mulz = Vector.fold1ZipWith (\c a b -> biMulAdd a b c) (..*)

#ifdef ML_KEM_TESTING
transpose :: (KnownNat m, KnownNat n) => Vector m (Vector n ty) -> Vector n (Vector m ty)
transpose a = create $ \(Offset j) (Offset i) -> index a (Offset i) (Offset j)
#endif