3 files changed, 61 insertions, 18 deletions

diff --git a/packages/base/src/Internal/Algorithms.hs b/packages/base/src/Internal/Algorithms.hs
index aaf6fbb..1235da3 100644
--- a/packages/base/src/Internal/Algorithms.hs
+++ b/packages/base/src/Internal/Algorithms.hs
@@ -29,7 +29,9 @@ import Internal.Conversion
 import Internal.LAPACK as LAPACK
 import Internal.Numeric
 import Data.List(foldl1')
-import Data.Array
+import qualified Data.Array as A
+import Internal.ST
+import Internal.Vectorized(range)
 
 {- | Generic linear algebra functions for double precision real and complex matrices.
 
@@ -578,11 +580,6 @@ eps =  2.22044604925031e-16
 peps :: RealFloat x => x
 peps = x where x = 2.0 ** fromIntegral (1 - floatDigits x)
 
-
--- | The imaginary unit: @i = 0.0 :+ 1.0@
-i :: Complex Double
-i = 0:+1
-
 -----------------------------------------------------------------------
 
 -- | The nullspace of a matrix from its precomputed SVD decomposition.
@@ -796,13 +793,23 @@ signlp r vals = foldl f 1 (zip [0..r-1] vals)
     where f s (a,b) | a /= b    = -s
                     | otherwise =  s
 
-swap (arr,s) (a,b) | a /= b    = (arr // [(a, arr!b),(b,arr!a)],-s)
-                   | otherwise = (arr,s)
-
-fixPerm r vals = (fromColumns $ elems res, sign)
-    where v = [0..r-1]
-          s = toColumns (ident r)
-          (res,sign) = foldl swap (listArray (0,r-1) s, 1) (zip v vals)
+fixPerm r vals = (fromColumns $ A.elems res, sign)
+  where
+    v = [0..r-1]
+    t = toColumns (ident r)
+    (res,sign) = foldl swap (A.listArray (0,r-1) t, 1) (zip v vals)
+    swap (arr,s) (a,b)
+      | a /= b    = (arr A.// [(a, arr A.! b),(b,arr A.! a)],-s)
+      | otherwise = (arr,s)
+
+fixPerm' :: [Int] -> Vector I
+fixPerm' s = res $ mutable f s0
+  where
+    s0 = reshape 1 (range (length s))
+    res = flatten . fst
+    swap m i j = rowOper (SWAP i j AllCols) m
+    f :: (Num t, Element t) => (Int, Int) -> STMatrix s t -> ST s () -- needed because of TypeFamilies
+    f _ p = sequence_ $ zipWith (swap p) [0..] s
 
 triang r c h v = (r><c) [el s t | s<-[0..r-1], t<-[0..c-1]]
     where el p q = if q-p>=h then v else 1 - v
diff --git a/packages/base/src/Internal/Util.hs b/packages/base/src/Internal/Util.hs
index f08f710..d9777ae 100644
--- a/packages/base/src/Internal/Util.hs
+++ b/packages/base/src/Internal/Util.hs
@@ -1,6 +1,5 @@
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE FunctionalDependencies #-}
 {-# LANGUAGE ViewPatterns #-}
@@ -55,7 +54,7 @@ module Internal.Util(
     -- ** 2D
     corr2, conv2, separable,
     block2x2,block3x3,view1,unView1,foldMatrix,
-    gaussElim_1, gaussElim_2, gaussElim, luST
+    gaussElim_1, gaussElim_2, gaussElim, luST, luSolve'
 ) where
 
 import Internal.Vector
@@ -65,7 +64,7 @@ import Internal.Element
 import Internal.Container
 import Internal.Vectorized
 import Internal.IO
-import Internal.Algorithms hiding (i,Normed,swap,linearSolve')
+import Internal.Algorithms hiding (Normed,linearSolve',luSolve')
 import Numeric.Matrix()
 import Numeric.Vector()
 import Internal.Random
@@ -73,7 +72,7 @@ import Internal.Convolution
 import Control.Monad(when,forM_)
 import Text.Printf
 import Data.List.Split(splitOn)
-import Data.List(intercalate,sortBy)
+import Data.List(intercalate,sortBy,foldl')
 import Control.Arrow((&&&))
 import Data.Complex
 import Data.Function(on)
@@ -690,6 +689,42 @@ luST ok (r,_) x = do
 
 --------------------------------------------------------------------------------
 
+rowRange m = [0..rows m -1]
+
+at k = Pos (idxs[k])
+
+backSust lup rhs = foldl' f (rhs?[]) (reverse ls)
+  where
+    ls  = [ (d k , u k , b k) | k <- rowRange lup ]
+      where
+        d k = lup ?? (at k, at k)
+        u k = lup ?? (at k, Drop (k+1))
+        b k = rhs ?? (at k, All)
+    
+    f x (d,u,b) = (b - u<>x) / d
+                       ===
+                        x
+
+
+forwSust lup rhs = foldl' f (rhs?[]) ls
+  where
+    ls  = [ (l k , b k) | k <- rowRange lup ]
+      where
+        l k = lup ?? (at k, Take k)
+        b k = rhs ?? (at k, All)
+    
+    f x (l,b) =     x
+                   ===
+                (b - l<>x)
+
+
+luSolve' (lup,p) b = backSust lup (forwSust lup pb)
+  where
+    pb = b ?? (Pos (fixPerm' p), All)
+
+
+--------------------------------------------------------------------------------
+
 instance Testable (Matrix I) where
    checkT _ = test
 
diff --git a/packages/base/src/Numeric/LinearAlgebra.hs b/packages/base/src/Numeric/LinearAlgebra.hs
index 2e6b8ca..e899445 100644
--- a/packages/base/src/Numeric/LinearAlgebra.hs
+++ b/packages/base/src/Numeric/LinearAlgebra.hs
@@ -77,6 +77,7 @@ module Numeric.LinearAlgebra (
     linearSolveLS,
     linearSolveSVD,
     luSolve,
+    luSolve',
     cholSolve,
     cgSolve,
     cgSolve',
@@ -158,7 +159,7 @@ import Numeric.Vector()
 import Internal.Matrix
 import Internal.Container hiding ((<>))
 import Internal.Numeric hiding (mul)
-import Internal.Algorithms hiding (linearSolve,Normed,orth,luPacked',linearSolve')
+import Internal.Algorithms hiding (linearSolve,Normed,orth,luPacked',linearSolve',luSolve')
 import qualified Internal.Algorithms as A
 import Internal.Util
 import Internal.Random