{-# OPTIONS_GHC -fglasgow-exts #-}
-----------------------------------------------------------------------------
{- |
Module      :  Numeric.LinearAlgebra.Algorithms
Copyright   :  (c) Alberto Ruiz 2006-7
License     :  GPL-style

Maintainer  :  Alberto Ruiz (aruiz at um dot es)
Stability   :  provisional
Portability :  uses ffi

A generic interface for a number of essential functions. Using it some higher level algorithms
and testing properties can be written for both real and complex matrices.

In any case, the specific functions for particular base types can also be explicitly
imported from the LAPACK and GSL.Matrix modules.

-}
-----------------------------------------------------------------------------

module Numeric.LinearAlgebra.Algorithms (
-- * Linear Systems
    linearSolve,
    inv, pinv,
    pinvTol, det,
-- * Matrix factorizations
-- ** Singular value decomposition
    svd,
    full, economy,
-- ** Eigensystems
    eig, eigSH,
-- ** Other 
    Numeric.LinearAlgebra.Algorithms.qr, chol,
-- * Nullspace
    nullspacePrec,
    nullVector,
-- * Misc
    eps, i,
    ctrans,
    Normed(..), NormType(..),
    GenMat(linearSolveSVD,lu,eigSH')
) where


import Data.Packed.Internal hiding (fromComplex, toComplex, comp, conj)
import Data.Packed
import Numeric.GSL.Matrix(luR,luC,qr)
import Numeric.GSL.Vector
import Numeric.LinearAlgebra.LAPACK as LAPACK
import Complex
import Numeric.LinearAlgebra.Linear

-- | Auxiliary typeclass used to define generic computations for both real and complex matrices.
class (Linear Matrix t) => GenMat t where
    svd         :: Matrix t -> (Matrix t, Vector Double, Matrix t)
    lu          :: Matrix t -> (Matrix t, Matrix t, [Int], t)
    linearSolve :: Matrix t -> Matrix t -> Matrix t
    linearSolveSVD :: Matrix t -> Matrix t -> Matrix t
    eig         :: Matrix t -> (Vector (Complex Double), Matrix (Complex Double))
    eigSH'      :: Matrix t -> (Vector Double, Matrix t)
    cholSH      :: Matrix t -> Matrix t
    -- | conjugate transpose
    ctrans :: Matrix t -> Matrix t

instance GenMat Double where
    svd = svdR
    lu  = luR
    linearSolve = linearSolveR
    linearSolveSVD = linearSolveSVDR Nothing
    ctrans = trans
    eig = eigR
    eigSH' = eigS
    cholSH = cholS

instance GenMat (Complex Double) where
    svd = svdC
    lu  = luC
    linearSolve = linearSolveC
    linearSolveSVD = linearSolveSVDC Nothing
    ctrans = conjTrans
    eig = eigC
    eigSH' = eigH
    cholSH = cholH

-- | eigensystem of complex hermitian or real symmetric matrix
eigSH :: GenMat t => Matrix t -> (Vector Double, Matrix t)
eigSH m | m `equal` ctrans m = eigSH' m
        | otherwise = error "eigSH requires complex hermitian or real symmetric matrix"

-- | Cholesky factorization of a positive definite hermitian or symmetric matrix
chol :: GenMat t => Matrix t ->  Matrix t
chol m | m `equal` ctrans m = cholSH m
       | otherwise = error "chol requires positive definite complex hermitian or real symmetric matrix"

qr :: Matrix Double -> (Matrix Double, Matrix Double)
qr = Numeric.GSL.Matrix.qr

square m = rows m == cols m

det :: GenMat t => Matrix t -> t
det m | square m = s * (product $ toList $ takeDiag $ u)
      | otherwise = error "det of nonsquare matrix"
    where (_,u,_,s) = lu m

inv :: GenMat t => Matrix t -> Matrix t
inv m | square m = m `linearSolve` ident (rows m)
      | otherwise = error "inv of nonsquare matrix"

pinv :: GenMat t => Matrix t -> Matrix t
pinv m = linearSolveSVD m (ident (rows m))

full :: Field t 
     => (Matrix t -> (Matrix t, Vector Double, Matrix t)) -> Matrix t -> (Matrix t, Matrix Double, Matrix t)
full svd m = (u, d ,v) where
    (u,s,v) = svd m
    d = diagRect s r c
    r = rows m
    c = cols m

economy :: Field t 
        => (Matrix t -> (Matrix t, Vector Double, Matrix t)) -> Matrix t -> (Matrix t, Vector Double, Matrix t)
economy svd m = (u', subVector 0 d s, v') where
    (u,s,v) = svd m
    sl@(g:_) = toList (complex s)
    s' = fromList . filter rec $ sl
    rec x = magnitude x > magnitude g*tol
    t = 1
    tol = (fromIntegral (max (rows m) (cols m)) * magnitude g * t * eps)
    r = rows m
    c = cols m
    d = dim s'
    u' = takeColumns d u
    v' = takeColumns d v


-- | The machine precision of a Double: @eps == 2.22044604925031e-16@ (the value used by GNU-Octave).
eps :: Double
eps =  2.22044604925031e-16

-- | The imaginary unit: @i == 0.0 :+ 1.0@
i :: Complex Double
i = 0:+1


-- | matrix product
mXm :: (Num t, GenMat t) => Matrix t -> Matrix t -> Matrix t
mXm = multiply

-- | matrix - vector product
mXv :: (Num t, GenMat t) => Matrix t -> Vector t -> Vector t
mXv m v = flatten $ m `mXm` (asColumn v)

-- | vector - matrix product
vXm :: (Num t, GenMat t) => Vector t -> Matrix t -> Vector t
vXm v m = flatten $ (asRow v) `mXm` m


---------------------------------------------------------------------------

norm2 :: Vector Double -> Double
norm2 = toScalarR Norm2

norm1 :: Vector Double -> Double
norm1 = toScalarR AbsSum

data NormType = Infinity | PNorm1 | PNorm2 -- PNorm Int

pnormRV PNorm2 = norm2
pnormRV PNorm1 = norm1
pnormRV Infinity = vectorMax . vectorMapR Abs
--pnormRV _ = error "pnormRV not yet defined"

pnormCV PNorm2 = norm2 . asReal
pnormCV PNorm1 = norm1 . liftVector magnitude
pnormCV Infinity = vectorMax . liftVector magnitude
--pnormCV _ = error "pnormCV not yet defined"

pnormRM PNorm2 m = head (toList s) where (_,s,_) = svdR m
pnormRM PNorm1 m = vectorMax $ constant 1 (rows m) `vXm` liftMatrix (vectorMapR Abs) m
pnormRM Infinity m = vectorMax $ liftMatrix (vectorMapR Abs) m `mXv` constant 1 (cols m)
--pnormRM _ _ = error "p norm not yet defined"

pnormCM PNorm2 m = head (toList s) where (_,s,_) = svdC m
pnormCM PNorm1 m = vectorMax $ constant 1 (rows m) `vXm` liftMatrix (liftVector magnitude) m
pnormCM Infinity m = vectorMax $ liftMatrix (liftVector magnitude) m `mXv` constant 1 (cols m)
--pnormCM _ _ = error "p norm not yet defined"

-- -- | computes the p-norm of a matrix or vector (with the same definitions as GNU-octave). pnorm 0 denotes \\inf-norm. See also 'norm'.
--pnorm :: (Container t, GenMat a) => Int -> t a -> Double
--pnorm = pnormG

class Normed t where
    pnorm :: NormType -> t -> Double
    norm :: t -> Double
    norm = pnorm PNorm2

instance Normed (Vector Double) where
    pnorm = pnormRV

instance Normed (Vector (Complex Double)) where
    pnorm = pnormCV

instance Normed (Matrix Double) where
    pnorm = pnormRM

instance Normed (Matrix (Complex Double)) where
    pnorm = pnormCM

-----------------------------------------------------------------------

-- | The nullspace of a matrix from its SVD decomposition.
nullspacePrec :: GenMat t
              => Double          -- ^ relative tolerance in 'eps' units
              -> Matrix t   -- ^ input matrix
              -> [Vector t] -- ^ list of unitary vectors spanning the nullspace
nullspacePrec t m = ns where
    (_,s,v) = svd m
    sl@(g:_) = toList s
    tol = (fromIntegral (max (rows m) (cols m)) * g * t * eps)
    rank = length (filter (> g*tol) sl)
--    ns = drop rank (toColumns v)
    ns = drop rank $ toRows $ ctrans v

-- | The nullspace of a matrix, assumed to be one-dimensional, with default tolerance (shortcut for @last . nullspacePrec 1@).
nullVector :: GenMat t => Matrix t -> Vector t
nullVector = last . nullspacePrec 1

------------------------------------------------------------------------

{-  Pseudoinverse of a real matrix with the desired tolerance, expressed as a
multiplicative factor of the default tolerance used by GNU-Octave (see 'pinv').

@\> let m = 'fromLists' [[1,0,    0]
                    ,[0,1,    0]
                    ,[0,0,1e-10]]
\ 
\> 'pinv' m 
1. 0.           0.
0. 1.           0.
0. 0. 10000000000.
\ 
\> pinvTol 1E8 m
1. 0. 0.
0. 1. 0.
0. 0. 1.@

-}
--pinvTol :: Double -> Matrix Double -> Matrix Double
pinvTol t m = v' `mXm` diag s' `mXm` trans u' where
    (u,s,v) = svdR m
    sl@(g:_) = toList s
    s' = fromList . map rec $ sl
    rec x = if x < g*tol then 1 else 1/x
    tol = (fromIntegral (max (rows m) (cols m)) * g * t * eps)
    r = rows m
    c = cols m
    d = dim s
    u' = takeColumns d u
    v' = takeColumns d v