SRC/chetri2x.f(3)

💖 NAME 💖

okay bestie, welcome to the SRC/chetri2x.f(3) page — the manual name is the Library Functions Manual, and we’re folding that in right here instead of copying the header line. This page is literally SRC/chetri2x.f, and its main-character routine is chetri2x / CHETRI2X. No cap. 💅

✨ SYNOPSIS ✨

🦋 Functions/Subroutines 🦋

subroutine chetri2x (uplo, n, a, lda, ipiv, work, nb, info)
    CHETRI2X

💅 Function/Subroutine Documentation 💅

subroutine chetri2x (character uplo, integer n, complex, dimension( lda, * )
a, integer lda, integer, dimension( * ) ipiv, complex, dimension(
n+nb+1,* ) work, integer nb, integer info)
    CHETRI2X

🎀 Purpose 🎀

okay so CHETRI2X computes the inverse of a complex Hermitian indefinite matrix A using the factorization A = U*D*U**H or A = L*D*L**H computed by CHETRF. That’s the whole flex. 💖

🌸 Parameters 🌸

• UPLO — CHARACTER*1. This cutie specifies whether the details of the factorization are stored as an upper or lower triangular matrix. The values are:
  • 'U': upper triangular, form is A = U*D*U**H;
  • 'L': lower triangular, form is A = L*D*L**H.
• N — INTEGER. The order of the matrix A. Constraint: N >= 0.
• A — COMPLEX array, dimension (LDA,N). On entry, this is the NNB diagonal matrix D and the multipliers used to obtain the factor U or L as computed by CHETRF. On exit, if INFO = 0, it’s the (symmetric) inverse of the original matrix. If UPLO = 'U', the upper triangular part of the inverse is formed and the part of A below the diagonal is not referenced; if UPLO = 'L', the lower triangular part of the inverse is formed and the part of A above the diagonal is not referenced. 💅
• LDA — INTEGER. The leading dimension of the array A. Constraint: LDA >= max(1,N).
• IPIV — INTEGER array, dimension (N). Details of the interchanges and the NNB structure of D as determined by CHETRF.
• WORK — COMPLEX array, dimension (N+NB+1,NB+3).
• NB — INTEGER. Block size.
• INFO — INTEGER. Exit-status tea:
  • = 0: successful exit;
  • < 0: if INFO = -i, the i-th argument had an illegal value;
  • > 0: if INFO = i, D(i,i) = 0; the matrix is singular and its inverse could not be computed. 😭

👑 Author 👑

• Univ. of Tennessee
• Univ. of California Berkeley
• Univ. of Colorado Denver
• NAG Ltd.

Definition at line 119 of file chetri2x.f.

🫶 Author 🫶

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