/home/abui.../zsytri2.f(3)

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💅 bestie, welcome to the Library Functions Manual page for /home/abui.../zsytri2.f(3) — aka zsytri2.f(3). The header repeats that path like a chorus, but we’re folding it in here so it stays cute. ✨

🎀 NAME 🎀

/home/abuild/rpmbuild/BUILD/lapack-static-3.12.0-build/lapack-3.12.0/SRC/zsytri2.f — that’s the file this page is about, bestie. It’s giving LAPACK source-file realness, and the manual name is Library Functions Manual; the page path is /home/abui.../zsytri2.f(3).

✨ SYNOPSIS ✨

🦋 Functions/Subroutines 🦋

       subroutine ZSYTRI2 (uplo, n, a, lda, ipiv, work, lwork, info)
           ZSYTRI2

💅 Function/Subroutine Documentation 💅

   subroutine ZSYTRI2 (character uplo, integer n, complex*16, dimension( lda, *
       ) a, integer lda, integer, dimension( * ) ipiv, complex*16, dimension( *
       ) work, integer lwork, integer info)
       ZSYTRI2

🌸 Purpose 🌸

Okay so ZSYTRI2 computes the inverse of a COMPLEX*16 symmetric indefinite matrix A, using the factorization A = U*D*U**T or A = L*D*L**T computed by ZSYTRF. Then ZSYTRI2 sets the LEADING DIMENSION of the workspace before calling ZSYTRI2X, and ZSYTRI2X is the one that actually computes the inverse. Delegation slay. ✨

🎀 Parameters 🎀

UPLO

UPLO is CHARACTER*1 and tells us 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**T.
  • 'L': lower triangular, form is A = L*D*L**T.

N

N is INTEGER — the order of the matrix A, and N >= 0. Periodt.

A

A is a COMPLEX*16 array, dimension (LDA,N).

On entry, it holds the block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by ZSYTRF.

On exit, if INFO = 0, it holds 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. No cap.

LDA

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

IPIV

IPIV is an INTEGER array, dimension (N). It carries the details of the interchanges and the block structure of D as determined by ZSYTRF.

WORK

WORK is a COMPLEX*16 array, dimension (N+NB+1)*(NB+3).

LWORK

LWORK is INTEGER — the dimension of the array WORK. WORK is size >= (N+NB+1)*(NB+3).

If LDWORK = -1, then a workspace query is assumed; the routine 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 LDWORK 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, 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 126 of file zsytri2.f.

📜 Author 📜

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