SRC/chetrf_aa_2stage.f(3)

NAME
SRC/chetrf_aa_2stage.f

SYNOPSIS

  Functions/Subroutines
subroutine chetrf_aa_2stage (uplo, n, a, lda, tb, ltb, ipiv, ipiv2, work, lwork, info)
CHETRF_AA_2STAGE

Function/Subroutine Documentation

  subroutine chetrf_aa_2stage (character uplo, integer n, complex, dimension( lda, * ) a, integer lda, complex, dimension( * ) tb, integer ltb, integer, dimension( * ) ipiv, integer, dimension( * ) ipiv2, complex, dimension( * ) work, integer lwork, integer info)

CHETRF_AA_2STAGE

Purpose:

     CHETRF_AA_2STAGE computes the factorization of a real hermitian matrix A
     using the Aasen's algorithm.  The form of the factorization is
        A = U**T*T*U  or  A = L*T*L**T
     where U (or L) is a product of permutation and unit upper (lower)
     triangular matrices, and T is a hermitian band matrix with the
     bandwidth of NB (NB is internally selected and stored in TB( 1 ), and T is
     LU factorized with partial pivoting).
     This is the blocked version of the algorithm, calling Level 3 BLAS.

Parameters
    UPLO

              UPLO is CHARACTER*1
              = 'U':  Upper triangle of A is stored;
              = 'L':  Lower triangle of A is stored.

    N

              N is INTEGER
              The order of the matrix A.  N >= 0.

    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, L is stored below (or above) the subdiagonal blocks,
              when UPLO  is 'L' (or 'U').

    LDA

              LDA is INTEGER
              The leading dimension of the array A.  LDA >= max(1,N).

    TB

              TB is COMPLEX array, dimension (LTB)
              On exit, details of the LU factorization of the band matrix.

    LTB

              LTB is INTEGER
              The size of the array TB. LTB >= 4*N, internally
              used to select NB such that LTB >= (3*NB+1)*N.
              If LTB = -1, then a workspace query is assumed; the
              routine only calculates the optimal size of LTB,
              returns this value as the first entry of TB, and
              no error message related to LTB is issued by XERBLA.

    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).

    IPIV2

              IPIV2 is INTEGER array, dimension (N)
              On exit, it contains the details of the interchanges, i.e.,
              the row and column k of T were interchanged with the
              row and column IPIV(k).

    WORK

              WORK is COMPLEX workspace of size LWORK

    LWORK

              LWORK is INTEGER
              The size of WORK. LWORK >= N, internally used to select NB
              such that LWORK >= N*NB.
              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.

    INFO

              INFO is INTEGER
              = 0:  successful exit
              < 0:  if INFO = -i, the i-th argument had an illegal value.
              > 0:  if INFO = i, band LU factorization failed on i-th column

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Definition at line 158 of file chetrf_aa_2stage.f.

Author

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