4 files changed, 62 insertions, 3 deletions

diff --git a/lib/Numeric/LinearAlgebra/Algorithms.hs b/lib/Numeric/LinearAlgebra/Algorithms.hs
index 6b0fb08..0f2ccef 100644
--- a/lib/Numeric/LinearAlgebra/Algorithms.hs
+++ b/lib/Numeric/LinearAlgebra/Algorithms.hs
@@ -27,6 +27,7 @@ module Numeric.LinearAlgebra.Algorithms (
 -- * Linear Systems
     linearSolve,
     luSolve,
+    cholSolve,
     linearSolveLS,
     linearSolveSVD,
     inv, pinv,
@@ -91,6 +92,7 @@ class (Normed (Matrix t), Linear Vector t, Linear Matrix t) => Field t where
     luPacked'    :: Matrix t -> (Matrix t, [Int])
     luSolve'     :: (Matrix t, [Int]) -> Matrix t -> Matrix t
     linearSolve' :: Matrix t -> Matrix t -> Matrix t
+    cholSolve'   :: Matrix t -> Matrix t -> Matrix t
     linearSolveSVD' :: Matrix t -> Matrix t -> Matrix t
     linearSolveLS'  :: Matrix t -> Matrix t -> Matrix t
     eig'         :: Matrix t -> (Vector (Complex Double), Matrix (Complex Double))
@@ -112,6 +114,7 @@ instance Field Double where
     luPacked' = luR
     luSolve' (l_u,perm) = lusR l_u perm
     linearSolve' = linearSolveR                 -- (luSolve . luPacked) ??
+    cholSolve' = cholSolveR
     linearSolveLS' = linearSolveLSR
     linearSolveSVD' = linearSolveSVDR Nothing
     ctrans' = trans
@@ -132,6 +135,7 @@ instance Field (Complex Double) where
     luPacked' = luC
     luSolve' (l_u,perm) = lusC l_u perm
     linearSolve' = linearSolveC
+    cholSolve' = cholSolveC
     linearSolveLS' = linearSolveLSC
     linearSolveSVD' = linearSolveSVDC Nothing
     ctrans' = conj . trans
@@ -229,6 +233,10 @@ luSolve = luSolve'
 linearSolve :: Field t => Matrix t -> Matrix t -> Matrix t
 linearSolve = linearSolve'
 
+-- | Solve a symmetric or Hermitian positive definite linear system using a precomputed Cholesky decomposition obtained by 'chol'.
+cholSolve :: Field t => Matrix t -> Matrix t -> Matrix t
+cholSolve = cholSolve'
+
 -- | Minimum norm solution of a general linear least squares problem Ax=B using the SVD. Admits rank-deficient systems but it is slower than 'linearSolveLS'. The effective rank of A is determined by treating as zero those singular valures which are less than 'eps' times the largest singular value.
 linearSolveSVD :: Field t => Matrix t -> Matrix t -> Matrix t
 linearSolveSVD = linearSolveSVD'
@@ -322,7 +330,7 @@ cholSH = cholSH'
 
 -- | Cholesky factorization of a positive definite hermitian or symmetric matrix.
 --
--- If @c = chol m@ then @m == ctrans c \<> c@.
+-- If @c = chol m@ then @c@ is upper triangular and @m == ctrans c \<> c@.
 chol :: Field t => Matrix t ->  Matrix t
 chol m | exactHermitian m = cholSH m
        | otherwise = error "chol requires positive definite complex hermitian or real symmetric matrix"
diff --git a/lib/Numeric/LinearAlgebra/LAPACK.hs b/lib/Numeric/LinearAlgebra/LAPACK.hs
index a1ac1cf..5d4eb0d 100644
--- a/lib/Numeric/LinearAlgebra/LAPACK.hs
+++ b/lib/Numeric/LinearAlgebra/LAPACK.hs
@@ -18,6 +18,7 @@ module Numeric.LinearAlgebra.LAPACK (
     -- * Linear systems
     linearSolveR, linearSolveC,
     lusR, lusC,
+    cholSolveR, cholSolveC,
     linearSolveLSR, linearSolveLSC,
     linearSolveSVDR, linearSolveSVDC,
     -- * SVD
@@ -312,8 +313,10 @@ eigOnlyH = vrev . fst. eigSHAux (zheev 1) "eigH'" . fmat
 vrev = flatten . flipud . reshape 1
 
 -----------------------------------------------------------------------------
-foreign import ccall "LAPACK/lapack-aux.h linearSolveR_l" dgesv :: TMMM
-foreign import ccall "LAPACK/lapack-aux.h linearSolveC_l" zgesv :: TCMCMCM
+foreign import ccall "linearSolveR_l" dgesv :: TMMM
+foreign import ccall "linearSolveC_l" zgesv :: TCMCMCM
+foreign import ccall "cholSolveR_l" dpotrs :: TMMM
+foreign import ccall "cholSolveC_l" zpotrs :: TCMCMCM
 
 linearSolveSQAux f st a b
     | n1==n2 && n1==r = unsafePerformIO $ do
@@ -334,6 +337,15 @@ linearSolveR a b = linearSolveSQAux dgesv "linearSolveR" (fmat a) (fmat b)
 linearSolveC :: Matrix (Complex Double) -> Matrix (Complex Double) -> Matrix (Complex Double)
 linearSolveC a b = linearSolveSQAux zgesv "linearSolveC" (fmat a) (fmat b)
 
+
+-- | Solves a symmetric positive definite system of linear equations using a precomputed Cholesky factorization obtained by 'cholS'.
+cholSolveR :: Matrix Double -> Matrix Double -> Matrix Double
+cholSolveR a b = linearSolveSQAux dpotrs "cholSolveR" (fmat a) (fmat b)
+
+-- | Solves a Hermitian positive definite system of linear equations using a precomputed Cholesky factorization obtained by 'cholH'.
+cholSolveC :: Matrix (Complex Double) -> Matrix (Complex Double) -> Matrix (Complex Double)
+cholSolveC a b = linearSolveSQAux zpotrs "cholSolveC" (fmat a) (fmat b)
+
 -----------------------------------------------------------------------------------
 foreign import ccall "LAPACK/lapack-aux.h linearSolveLSR_l" dgels :: TMMM
 foreign import ccall "LAPACK/lapack-aux.h linearSolveLSC_l" zgels :: TCMCMCM
diff --git a/lib/Numeric/LinearAlgebra/LAPACK/lapack-aux.c b/lib/Numeric/LinearAlgebra/LAPACK/lapack-aux.c
index 06c2479..fd840e3 100644
--- a/lib/Numeric/LinearAlgebra/LAPACK/lapack-aux.c
+++ b/lib/Numeric/LinearAlgebra/LAPACK/lapack-aux.c
@@ -492,6 +492,42 @@ int linearSolveC_l(KCMAT(a),KCMAT(b),CMAT(x)) {
     OK
 }
 
+//////// symmetric positive definite real linear system using Cholesky ////////////
+
+int cholSolveR_l(KDMAT(a),KDMAT(b),DMAT(x)) {
+    integer n = ar;
+    integer nhrs = bc;
+    REQUIRES(n>=1 && ar==ac && ar==br,BAD_SIZE);
+    DEBUGMSG("cholSolveR_l");
+    memcpy(xp,bp,n*nhrs*sizeof(double));
+    integer res;
+    dpotrs_ ("U",
+             &n,&nhrs,
+             (double*)ap, &n,
+             xp, &n,
+             &res);
+    CHECK(res,res);
+    OK
+}
+
+//////// Hermitian positive definite real linear system using Cholesky ////////////
+
+int cholSolveC_l(KCMAT(a),KCMAT(b),CMAT(x)) {
+    integer n = ar;
+    integer nhrs = bc;
+    REQUIRES(n>=1 && ar==ac && ar==br,BAD_SIZE);
+    DEBUGMSG("cholSolveC_l");
+    memcpy(xp,bp,2*n*nhrs*sizeof(double));
+    integer res;
+    zpotrs_  ("U",
+             &n,&nhrs,
+             (doublecomplex*)ap, &n,
+             (doublecomplex*)xp, &n,
+             &res);
+    CHECK(res,res);
+    OK
+}
+
 //////////////////// least squares real linear system ////////////
 
 int linearSolveLSR_l(KDMAT(a),KDMAT(b),DMAT(x)) {
diff --git a/lib/Numeric/LinearAlgebra/Tests.hs b/lib/Numeric/LinearAlgebra/Tests.hs
index f8f8bd5..36efab6 100644
--- a/lib/Numeric/LinearAlgebra/Tests.hs
+++ b/lib/Numeric/LinearAlgebra/Tests.hs
@@ -208,6 +208,9 @@ runTests n = do
     putStrLn "------ luSolve"
     test (linearSolveProp (luSolve.luPacked) . rSqWC)
     test (linearSolveProp (luSolve.luPacked) . cSqWC)
+    putStrLn "------ cholSolve"
+    test (linearSolveProp (cholSolve.chol) . rPosDef)
+    test (linearSolveProp (cholSolve.chol) . cPosDef)
     putStrLn "------ luSolveLS"
     test (linearSolveProp linearSolveLS . rSqWC)
     test (linearSolveProp linearSolveLS . cSqWC)