HECON_ROOK - 5.2 English - 68552

AOCL API Guide (68552)

Document ID
68552
Release Date
2025-12-29
Version
5.2 English
template<typename T, typename Ta>
void hecon_rook(char *uplo, integer *n, T *a, integer *lda, integer *ipiv, Ta *anorm, Ta *rcond, T *work, integer *info)#

HECON_ROOK estimates the reciprocal of the condition number fort HE matrices

using factorization obtained with one of the bounded diagonal pivoting methods (max 2 interchanges)

Purpose:

   HECON_ROOK estimates the reciprocal of the condition number of a complex
   Hermitian matrix A using the factorization A = U*D*U**H or
   A = L*D*L**H computed by CHETRF_ROOK.

   An estimate is obtained for norm(inv(A)), and the reciprocal of the
   condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))).
Parameters:
  • UPLO[in]

    UPLO is CHARACTER*1

    Specifies whether the details of the factorization are stored as an upper or lower triangular matrix.

    = ‘U’: Upper triangular, form is A = U*D*U**H;

    = ‘L’: Lower triangular, form is A = L*D*L**H.

  • N[in]

    N is INTEGER

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

  • A[in]

    A is COMPLEX array, dimension (LDA,N)

    The block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by CHETRF_ROOK.

  • LDA[in]

    LDA is INTEGER

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

  • IPIV[in]

    IPIV is INTEGER array, dimension (N)

    Details of the interchanges and the block structure of D as determined by CHETRF_ROOK.

  • ANORM[in]

    ANORM is REAL

    The 1-norm of the original matrix A.

  • RCOND[out]

    RCOND is REAL

    The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is an estimate of the 1-norm of inv(A) computed in this routine.

  • WORK[out] WORK is COMPLEX array, dimension (2*N)

  • INFO[out]

    INFO is INTEGER

    = 0: successful exit

    < 0: if INFO = -i, the i-th argument had an illegal value