chetrf_aa()

subroutine chetrf_aa	(	character	uplo,
		integer	n,
		complex, dimension( lda, * )	a,
		integer	lda,
		integer, dimension( * )	ipiv,
		complex, dimension( * )	work,
		integer	lwork,
		integer	info )

CHETRF_AA

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Purpose:

!>
!> CHETRF_AA computes the factorization of a complex hermitian matrix A
!> using the Aasen's algorithm.  The form of the factorization is
!>
!>    A = U**H*T*U  or  A = L*T*L**H
!>
!> where U (or L) is a product of permutation and unit upper (lower)
!> triangular matrices, and T is a hermitian tridiagonal matrix.
!>
!> This is the blocked version of the algorithm, calling Level 3 BLAS.
!> 

Parameters

[in]	UPLO	!> UPLO is CHARACTER*1 !> = 'U': Upper triangle of A is stored; !> = 'L': Lower triangle of A is stored. !>
[in]	N	!> N is INTEGER !> The order of the matrix A. N >= 0. !>
[in,out]	A	!> A is COMPLEX array, dimension (LDA,N) !> On entry, the hermitian matrix A. If UPLO = 'U', the leading !> N-by-N upper triangular part of A contains the upper !> triangular part of the matrix A, and the strictly lower !> triangular part of A is not referenced. If UPLO = 'L', the !> leading N-by-N lower triangular part of A contains the lower !> triangular part of the matrix A, and the strictly upper !> triangular part of A is not referenced. !> !> On exit, the tridiagonal matrix is stored in the diagonals !> and the subdiagonals of A just below (or above) the diagonals, !> and L is stored below (or above) the subdiagonals, when UPLO !> is 'L' (or 'U'). !>
[in]	LDA	!> LDA is INTEGER !> The leading dimension of the array A. LDA >= max(1,N). !>
[out]	IPIV	!> IPIV is INTEGER array, dimension (N) !> On exit, it contains the details of the interchanges, i.e., !> the row and column k of A were interchanged with the !> row and column IPIV(k). !>
[out]	WORK	!> WORK is COMPLEX array, dimension (MAX(1,LWORK)) !> On exit, if INFO = 0, WORK(1) returns the optimal LWORK. !>
[in]	LWORK	!> LWORK is INTEGER !> The length of WORK. !> LWORK >= 1, if N <= 1, and LWORK >= 2*N, otherwise. !> For optimum performance LWORK >= N*(1+NB), where NB is !> the optimal blocksize, returned by ILAENV. !> !> If LWORK = -1, then a workspace query is assumed; the routine !> only calculates the optimal size of the WORK array, returns !> this value as the first entry of the WORK array, and no error !> message related to LWORK is issued by XERBLA. !>
[out]	INFO	!> INFO is INTEGER !> = 0: successful exit !> < 0: if INFO = -i, the i-th argument had an illegal value. !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.